Science – Grade 7 Learner’s Material First Edition, 2013 ISBN: ___________ Republic Act 8293, section 176 states that: No copyright shall subsist in any work of the Government of the Philippines. However, prior approval of the government agency or office wherein the work is created shall be necessary for exploitation of such work for profit. Such agency or office may, among other things, impose as a condition the payment of royalties. The borrowed materials (i.e., songs, stories, poems, pictures, photos, brand names, trademarks, etc.) included in this book are owned by their respective copyright holders. The publisher and authors do not represent nor claim ownership over them. Published by the Department of Education Secretary: Br. Armin A. Luistro FSC Undersecretary: Dr. Yolanda S. Quijano Assistant Secretary: Dr. Elena R. Ruiz
Development Team of the Learner’s Material Consultant: Merle C. Tan, Ph.D. Authors: Alvie J. Asuncion, Maria Helen D.H. Catalan, Ph.D., Leticia V. Catris, Ph.D., Marlene B. Ferido, Ph.D., Jacqueline Rose M. Gutierrez, Michael Anthony B. Mantala, Cerilina M. Maramag, Ivy P. Mejia, Eligio C. Obille, Jr., Risa L. Reyes, Ph.D., Ma. Dulcelina O. Sebastian, Merle C. Tan, Ph.D., and Rodolfo S. Treyes, Ph.D. Editors: Josefina Ll. Pabellon, Ph.D., Ma. Cristina D. Padolina, Ph.D., Risa L. Reyes, Ph.D., and Merle C. Tan, Ph.D. Reviewers: Magno R. Abueme, Ruby D. Arre, Bonifacio D. Caculitan, Jr., Marivic Rosales, and Arnold Sinen Illustrator: Alvin J. Encarnacion Layout Artists and Encoders: Rosita R. Cruz, Aro R. Rara, and Cecile N. Sales
Printed in the Philippines by ____________ Department of Education-Instructional Materials Council Secretariat (DepEd-IMCS) Office Address: Telefax: E-mail Address:
2nd Floor Dorm G, Philsports Complex, Meralco Avenue, Pasig City, Philippines 1600 (02) 634-1054, 634-1072
[email protected]
ii
Page Module 1. Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Activity 1: What solutions do you find in your home? . . . . . . . . . . . . . . . . . . . 4 Activity 2: What are some properties of solutions? . . . . . . . . . . . . . . . . . . . . . 5 Activity 3: What is the evidence that a solution is saturated? . . . . . . . . . . . . 8 Activity 4: Size matters! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Activity 5: How fast does coffee dissolve in hot water? In cold water? . . . . . 13 Activity 6: Which dissolves faster in hot and in cold water: Sugar or salt?. . . 14 Module 2. Substances and Mixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Activity 1: Seawater! See water and salts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Activity 2: Looks may be deceiving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Activity 3: My unknown sample: Substance or mixture? . . . . . . . . . . . . . . . .
16 17 20 25
Module 3. Elements and Compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Activity 1: Water, “wat-er” you made of? . . . . . . . . . . . . . . . . . . . . . . . . . . . . Activity 2: The periodic table: It’s element-ary! . . . . . . . . . . . . . . . . . . . . . . . . Activity 3: The “matter” on labels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Activity 4: The iron-y of food fortification . . . . . . . . . . . . . . . . . . . . . . . . . . . .
27 28 32 35 41
Module 4. Acids and Bases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Activity 1: How can you tell if a mixture is acidic or basic? . . . . . . . . . . . . . . . Activity 2: Color range, pH scale! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Activity 3: What happens to a metal when exposed to an acidic mixture? . .
43 44 50 53
Module 5. Metals and Nonmetals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 Activity 1: What can conduct electricity, metals or nonmetals? . . . . . . . . . . . 58 Activity 2: Acidity of the oxides of metals and nonmetals . . . . . . . . . . . . . . . . 63
Module 1. From Cell to Organism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 Activity 1: What makes up and organism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 Activity 2: Levels of organization in an organism . . . . . . . . . . . . . . . . . . . . . . . 75 Module 2. Plant and Animal Cells. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Activity 1: Comparing plant and animal cells . . . . . . . . . . . . . . . . . . . . . . . . . . Activity 2: Investigating plant cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . How to use the light microscope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
79 80 83 87
Module 3. Living Things Other than Plants and Animals . . . . . . . . . . . . . . . . . . . . 95 Activity 1: Are these also plants? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 Activity 2: What other livings things are found in the school grounds? . . . . . 99 Activity 3: What do these living things look like under the microscope? . . . . 101 Module 4. Reproduction: The Continuity of Life. . . . . . . . . . . . . . . . . . . . . . . . . . . Activity 1: Can you grow new plants from the eyes? . . . . . . . . . . . . . . . . . . . . Activity 2: Can one become two?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Activity 3: Structure of a gumamela flower. . . . . . . . . . . . . . . . . . . . . . . . . . . .
103 104 106 109
Module 5. Interactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 Activity 1: What does it mean to be alive? . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112 Activity 2: Housemates? Ecomates!. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 Activity 3: Which eats what?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 Activity 4: What to do with food wastes?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
Module 1. Describing Motion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 Activity 1: Where is it?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 Activity 2: My home to school roadmap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 Activity 3: Fun walk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 Activity 4: Doing detective work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 Module 2. Waves Around You . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Activity 1: Let’s makes waves! What happens when waves pass by? . . . . . . Activity 2: Anatomy of a wave. How do you describe waves? . . . . . . . . . . . . Activity 3: Mechanical vs. electromagnetic waves. How do waves propagate?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
145 146 151
Module 3. Sound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Activity 1: My own sounding box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Activity 2: Properties and characteristics of sound . . . . . . . . . . . . . . . . . . . . . Activity 3: Big time gig! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
161 162 165 170
155
Module 4. Light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . 173 Activity 1: Light sources: Langis, kandila or lampara . . . . . . . . . . . . . . . . . . . . 174 Activity 2: My spectrum wheel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 Activity 3: Colors of light – color of life! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 Activity 4: Light up straight!. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 Module 5. Heat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Activity 1: Warm me up, cool me down . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Activity 2: Which feels colder? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Activity 3: Move me up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv
187 188 191 193
Activity 4: Keep it cold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195 Activity 5: All at once . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196 Module 6. Electricity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Activity 1: Charged interactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Activity 2: To charge or not to charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Activity 3: Pass the charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Activity 4: When lightning strikes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Activity 5: Let there be light! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
199 200 203 205 206 207
Module 1. The Philippine Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Activity 1: Where in the world is the Philippines (Part I). . . . . . . . . . . . . . . . . Activity 2: Where in the world is the Philippines (Part II) . . . . . . . . . . . . . . . . Activity 3: What are some factors that will affect the amount of water in watersheds? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Activity 4: How are soils formed from rocks? . . . . . . . . . . . . . . . . . . . . . . . . . . Activity 5: Where are the mineral deposits in the Philippines?. . . . . . . . . . . . Activity 6: How do people destroy natural resources? . . . . . . . . . . . . . . . . . . Activity 7: Are you ready for “Make-a-Difference” day . . . . . . . . . . . . . . . . .
211 211 214 219 220 222 232 233
Module 2. Solar Energy and the Atmosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235 Activity 1: What is the basis for dividing Earth’s atmosphere into layers? . . . 235 Activity 2: Does a greenhouse retain or release heat? . . . . . . . . . . . . . . . . . . . 237 Activity 3: What happens when air is heated? . . . . . . . . . . . . . . . . . . . . . . . . . 244 Activity 4: What happens to the air in the surroundings as warm air rises? 245 Activity 5: Which warms up faster? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247 Activity 6: In what direction do winds blow – from high to low pressure pressure area or vice versa? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251 Module 3. Seasons and Eclipses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257 Activity 1: Why do seasons change? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258 Activity 2: How does the length of daytime and nighttime affect the season? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262 Activity 3: Are there shadows in space? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264 Activity 4: Does a Bakunawa cause eclipses?. . . . . . . . . . . . . . . . . . . . . . . . . . . 269
v
2
Suggested time allotment: 5 to 6 hours
Unit 1 MODULE
1
SOLUTIONS
Overview In Grade 6, you have learned about different mixtures and their characteristics. You have done activities where you mixed a solid and a liquid or combined two different liquids. In the process of mixing, you have observed that these mixtures either form homogeneous or heterogeneous mixtures. You have seen that when all parts of the mixture have the same uniform appearance and properties, it is homogeneous. You also learned that when different parts of the mixture are visible to the unaided eye and these parts are obviously different from one another, it is heterogeneous. A heterogeneous mixture consists of two or more phases. An example of a heterogeneous mixture is ice cubes (solid phase) placed in a glass of drinking water (liquid phase). Solutions are homogeneous mixtures. When you put sugar into water, the solid becomes part of the liquid and cannot be seen. You can say that the sugar dissolves in water or the sugar is soluble in water. Solutions may be solids dissolved in liquids or gases dissolved in liquids. There are also solutions where a gas is dissolved in another gas, a liquid in another liquid or a solid in another solid. Gaseous, liquid, and solid solutions are all around you. Many commercial products are sold as solutions. In this module, you will identify some important properties of solutions using different methods. You will also learn how to report the amount of the components in a given volume of solution. Towards the end of the module, you will investigate the factors that affect how fast a solid dissolves in water. At the end of Module 1, you will be able to answer the following key questions.
What common properties do solutions have? Are solutions always liquid?
3
Activity 1 What solutions do you find in your home? Objectives: After performing this activity, you should be able to: 1. describe some observable characteristics or properties of common solutions found at home or in stores; and 2. present the data gathered in table form to show some properties of common solutions you observed.
Procedure: 1. With your group mates, write the names of the products or items brought from home and describe the characteristics of each of these products. You may make a table similar to the one below. Products Found at Home or in Stores
Characteristics
2. As you observe each product, describe the products in terms of color and appearance, odor, feel, and taste (for food products). 3. Based on what you have learned so far in Grade 6, which of the products you observed are homogeneous mixtures? What common characteristics do the homogeneous mixtures in your list have? 4. Which of these products or items are solutions?
A solution is not always a liquid; it can be solid, liquid, or gas. In addition, solutions may either be found in nature or are manufactured.
4
Naturally Occurring Solutions Many materials in nature can be used efficiently only when these are in the form of solutions. For example, plants cannot absorb minerals from the soil unless these minerals are in solution. Seawater is a solution having a higher percentage of salt and minerals than other sources of water like ground water or rivers. Rainwater is a solution containing dissolved gases like oxygen and carbon dioxide. Air is a mixture of gases. Water vapor is present in different amounts depending on the location. Air above big bodies of water contains more water vapor than air above deserts. Humidity is a measure of the amount of water vapor in air. Dry air consists of about 78% nitrogen, 21% oxygen, 1% argon, 0.04% carbon dioxide and traces of argon, helium, neon, krypton, and xenon. Useful solutions are found not only in nature; many solutions are made for a specific purpose.
Manufactured and Processed Solutions Almost every household uses vinegar for cooking and cleaning purposes. Vinegar usually contains about 5% acetic acid in water. Some samples of vinegar are clear homogeneous mixtures (solutions). Other kinds of vinegar are colloidal. A metal alloy is a solid solution made up of two or more metals or nonmetals. For example, bronze is an alloy of copper and tin. Brass is an alloy of copper and zinc. Other examples of solutions that are processed include wine and liquor, and tea (but not instant tea). In the next activity, you will predict what will happen when you mix a sample solid or liquid in a given volume of water. Investigate to find out if your predictions are correct. Explain your predictions using the evidence you have gathered from your investigation.
Activity 2 What are some properties of solutions? Objectives: When you finish this activity you should be able to: 1. compare the evidence gathered with the predictions you made; and
5
2. describe some properties of solutions based on observations.
Materials Needed:
6 cups water 6 pieces, spoons either of the following: cheesecloth (katsa), old, white T-shirt or filter paper 2 tablespoons each of the following: sugar, salt, mongo seeds, powdered juice, cooking oil, two different types of vinegar (one which is clear and another which appears cloudy) 12 clear bottles or cups or small beakers 2 pieces each, measuring spoons (½ tsp and 1tsp) 2 pieces each, measuring cups (½ cup and 1 cup) 3 funnels or improvised funnel made from 500 mL plastic bottle 1 funnel rack 1 flashlight
Procedure: 1.
Predict which among the given samples will dissolve in water. Write your predictions in column 2 of Table 1.
2.
Put one cup of water in each of the cups.
3.
Add ½ teaspoon of each of the seven samples. Stir the mixture with a teaspoon to dissolve as much of each sample as possible. Use a different teaspoon for each of the cups.
Q1. Describe the mixture that resulted after mixing. Write your answer in column 3. Q2. How many phases do you observe? Write your answer and observations in column 4. 4.
Filter the mixture with filter paper using a setup similar to Figure 1. You may use katsa or old, white T-shirt with the improvised funnel from plastic bottle.
Figure 1. A filtration setup. The funnel is supported on an iron ring and the filtrate is received in another container.* *Philippines. Department of Education. (2004). Chemistry: Science and Technology textbook for 3rd year. (Revised ed.). Quezon City: Author.
6
Table 1. Data table for Activity 2 (1) Sample solid or liquid
(2) Will dissolve in one cup water (yes or no)
(3) Appearance
(4) Number of phases
(5) Can be separated by filtration (yes or no)
(6) Path of light (can or cannot be seen)
(7) Solution or not?
Sugar Salt Mongo seeds Powdered juice Cooking oil Vinegar (clear type) Vinegar (cloudy) Note: In column 3, you may describe the mixture in other ways such as homogeneous or heterogeneous. You may also describe the color of the mixture. Q3. In which mixture were you able to separate the components by filtration? Write your observations in column 5 of Table 1. 5.
Place the liquid collected from each filtration in a small beaker or clear transparent glass bottle. Shine light through the liquid using a flashlight placed on the side of the beaker. The room where you are working should be dark. Using a black background may help you see the light across the liquid. If the room is not dark, you can put the setup inside a cabinet in your laboratory.
Q4. In Column 6, write whether the path of light can be seen across the liquid. Q5. Which of the samples are solutions? Write your answer in column 7. Q6. Based on Activity 2, what are some common characteristics of solutions you observed?
There are other ways of identifying a solution. You will learn these methods in Grades 8 and 9.
7
In general, a solution has two types of components: the solute and the solvent. The solute and the solvent dissolve in each other. The component present in small amount is called the solute. The particles of solute are dissolved in a solution. Usually, the solvent is the component present in greater amount. In Activity 2, sugar is the solute and water is the solvent. Solutes and solvents may be solids, liquids, or gases. In Activity 3, you will find out how much solute can dissolve in a given amount of solvent and find out the type of solution based on whether there is excess solute or not. At higher grade levels, you will learn more of the detailed processes that happen when a solute dissolves in a solvent.
Activity 3 What is the evidence that a solution is saturated? After performing this activity you will be able to: 1. determine how much solid solute dissolves in a given volume of water; and 2. describe the appearance of a saturated solution.
Materials Needed
6 teaspoons sugar 1 cup of water 1 measuring cup (1cup capacity) 1 measuring spoon (½ tsp capacity) 2 small clear, transparent bottle 2 stirrers 1 thermometer
Procedure: 1.
Put 20 mL (approximately 2 tablespoons) of water in a small clear transparent bottle. Add ½ teaspoon of sugar and stir.
Q1. What is the appearance of the solutions? Write your observations.
8
2.
To the sugar solution in step #1, add ½ teaspoon sugar, a small portion at a time and stir the solution to dissolve the sugar. At this point, you have added 1 teaspoon sugar.
3.
Add ½ teaspoon of sugar to the sugar solution in step #2 and stir the solution. At this point, you have added one and ½ teaspoons of sugar.
4.
Continue adding ½ teaspoon sugar to the same cup until the added sugar no longer dissolves.
Q2. How many teaspoons of sugar have you added until the sugar no longer dissolves? Note: In this step, you will observe that there is already excess sugar which did not dissolve. Q3. So, how many teaspoons of sugar dissolved completely in 20 mL of water? Note: This is now the maximum amount of sugar that will completely dissolve in 20 mL of water.
In Activity 3, you have observed that there is a maximum amount of solute that can dissolve in a given amount of solvent at a certain temperature. This is what is called the solubility of the solute. From your everyday experience, you also observe that there is a limit to the amount of sugar you can dissolve in a given amount of water. A solution that contains the maximum amount of solute dissolved by a given amount of solvent is called a saturated solution. If you add more solute to the solvent, it will no longer dissolve. The solution has reached its saturation point. The presence of an excess solid which can no longer dissolve is evidence that the solution is saturated. A solution is unsaturated when it contains less solute than the maximum amount it can dissolve at a given temperature. In Activity 3, it is difficult to conclude that the containers with all solids dissolved are unsaturated simply by observing them. Some of these may already hold the maximum amount of solute, which cannot be observed by the unaided eye. If they do, then these are classified as saturated solutions. A more measurable way to find out the solubility of a solute is to determine the maximum amount that can be dissolved in 100 g of solvent at a specific temperature. There are available data from chemistry books that give the solubility of common solutes at particular temperatures. Figure 2 shows the solubility of table salt at 25oC.
9
Figure 2. At 25oC, a saturated solution of table salt has only 36.0 g (3 tablespoons) dissolved in 100 mL of water. Any additional table salt will no longer dissolve.
Concentration of Solutions The concentration describes the relative amounts of solute and solvent in a given volume of solution. When there is a large amount of dissolved solute for a certain volume of solvent, the solution is concentrated. A dilute solution has a small amount of dissolved solute in comparison to the amount of solvent. You will be able to distinguish between concentrated and dilute solutions from a simple demonstration your teacher will perform. You will describe the concentrations of solutions qualitatively (by simply observing their appearance) and quantitatively (by comparing the number of drops per volume of water). From Part 1 of the demonstration, you were able to describe the solutions as having quantitative concentrations of 1 drop/50 mL and 10 drops/50 mL. Qualitatively, you were able to distinguish the bottle with 10 drops/50 mL more concentrated (darker) than the bottle with 1 drop/50 mL. Now that you have distinguished dilute from concentrated solutions qualitatively and quantitatively from your teacher’s demonstration, you can express concentration in other ways such as:
(1) (2)
percent by volume, which is the amount of solute in a given volume of solution expressed as grams solute per 100 milliliter of solution (g/100 mL), and percent by mass, which is the amount of solute in a given mass of solvent expressed as grams solute per 100 grams of solution.
10
Labels of products sold often show the concentrations of solutes expressed as percent (%) by volume or mass. The alcohol used as a disinfectant is a solution of 70% ethyl or isopropyl alcohol, meaning 70 mL alcohol. There are also solutions sold as 40% ethyl or isopropyl alcohol. Vinegar is often labelled as “5% acidity,” which means that it contains 5 grams of acetic acid in 100 g of vinegar. Pure gold is referred to as 24 karats. Jewelry that is said to be 18 karats contains 18 grams of gold for every 24 grams of the material, the remaining 6 grams consist of the other metal like copper or silver. This material has a concentration of 75% gold, that is, [18/24(100)]. A 14 karat (14K) gold contains 14 grams gold and 10 grams of another metal, making it 58.3% gold. The following sample problems show you that there is a way to know the exact ratio of solute to solvent, which specifies the concentration of a solution. Sample problem 1 How many mL of ethyl alcohol are present in a 50 mL bottle of a 70% alcohol solution? Calculation for sample problem 1 Since the given is a 70% alcohol solution, it means that 100 mL of the alcohol solution contains 70 mL ethyl alcohol. So, the following calculations show that in 50 mL of the alcohol solution, there is 35 mL ethyl alcohol. 50 mL rubbing alcohol x
70 mL ethyl alcohol = 35 mL ethyl alcohol 100 mL alcohol solution
All portions of a solution have the same concentration. The composition of one part is also the same as the composition of the other parts. But you can change the concentration of solutions. This means you can prepare different solutions of sugar in water of different concentrations (for example, 10%, 20%, or 30%). In the same way, you can prepare different solutions of salt in water. Sample problem 2 A one peso coin has a mass of 5.5 grams. How many grams of copper are in a one peso coin containing 75% copper by mass? Calculation for sample problem 2 75% by mass means 75 grams of copper in 100 grams of one peso coin.
11
So, a 5.4 grams one peso coin contains, 75 g copper x 5.4 g coin = 4.0 g copper 100 g coin
Factors Affecting How Fast a Solid Solute Dissolves In activities 4 to 6, you will investigate factors that affect how fast a solid solute dissolves in a given volume of water.
The Effect of Stirring Your teacher demonstrated the effect of stirring in mixing a solid in water. You observed that stirring makes the solid dissolve faster in the solvent. Were you able to explain why this is so?
The Effect of Particle Size In Activity 4, you will investigate how the size of the solid being dissolved affects how fast it dissolves in water.
Activity 4 Size matters! 1. Write a hypothesis in a testable form. Describe a test you could conduct to find out which dissolve faster: granules (uncrushed) of table salt or the same amount of crushed salt. 2. Identify variables (for example, amount of table salt) that you need to control in order to have a fair test. 3. Identify the dependent and independent variables. 4. List all the materials you need, including the amount and ask these from your teacher. 5. Be sure to record your observations and tabulate them. Write everything you observed during the dissolving test. 6. What is your conclusion? Does the size of the salt affect how fast it dissolves in water? 7. Does your conclusion support or reject your hypothesis?
12
8. Based on what you know about dissolving, try to explain your results.
To help you explain the process of dissolving, imagine that in a solution, the particles of the solute (table salt) and the solvent (water) are constantly moving. Water particles collide everywhere along the surface of the particles of table salt, especially on the corners and edges. This occurs at the surface of the solid solute when it comes in contact with the solvent. The particles on the corners and edges then break away from the crystal and become surrounded by the water particles. So the solute particles are separated by the solvent particles. Can you now explain why smaller pieces of salt dissolve faster than larger ones? You may use an illustration or diagram in your explanation.
The Effect of Temperature Temperature affects how fast a solid solute dissolves in water. Your solutions in Activity 3 were at room temperature. In Activity 5 you will investigate how fast coffee dissolves in cold and in hot water. At what temperature will sugar dissolve faster?
Activity 5 How fast does coffee dissolve in hot water? In cold water? 1. Discuss with your group mates how to answer the question for investigation, “How fast does coffee dissolve in hot water? In cold water?” Write your hypothesis in a testable form. Describe a test you could conduct to find out how fast coffee dissolves in cold and in hot water. Note: Do not use 3-in-1 coffee as your sample. Use coffee granules. 2. Identify variables (for example, amount of amount of coffee) that you need to control in order to have a fair test. 3. Identify the dependent and independent variables. 4. List all the materials you need, including the amount and ask these from your teacher. 5. Do your investigation using the proper measuring devices. Be sure to record your observations and tabulate them. Write everything you observed during the dissolving test. These observations are the evidence from which you can draw your conclusions.
13
6. What is your conclusion? Does coffee dissolve faster in cold or in hot water? Use the observations and results you recorded to explain your answer. 7. Does your conclusion support or reject your hypothesis? Explain your results.
The Nature of Solute In Activity 6, you will find out if: (1) sugar dissolves faster in hot than in cold water, and (2) salt dissolves faster in hot than in cold water.
Activity 6 Which dissolves faster in hot and in cold water: Sugar or salt? 1. Discuss with your group mates how you will do your investigation. 2. Write your hypothesis in a testable form. Describe a test you could conduct to find out answers to the given two questions above. 3. Identify variables (for example, amount of coffee) that you need to control in order to have a fair test. 4. Identify the dependent and independent variables. 5. List all the materials you need, including the amount and ask these from your teacher. 6. Do your investigation using the proper measuring devices. Be sure to record your observations and tabulate them. Write everything you observed during the dissolving test. These observations are the evidence from which you can draw your conclusions. 7. What is your conclusion? Does coffee dissolve faster in cold or in hot water? Use the observations and results you recorded to explain your answer. 8. Does your conclusion support or reject your hypothesis? Explain your results. The following questions can guide you: a. Does sugar dissolve faster in hot water than in cold water? Explain your answer, based on your observations from the investigation. b. Does salt dissolve faster in hot than in cold water? Explain your answer, based on your observations from the investigation.
14
c. Which is affected more by increasing the temperature of the water—how fast salt dissolves or how fast sugar dissolves? Explain your answer.
You learned from Activity 5 that in general, a solute dissolves faster in water when you increase the temperature. But the effect of temperature is not that simple. The type or nature of the solute will affect how fast it dissolves in water. You observed from Activity 6 that increasing the temperature either makes a solid dissolve faster or slower in water. For some solutes, increasing the temperature does not have any effect on how fast the solute dissolves. Now that you have completed the activities in this module, you have learned the properties of a solution, the ways of reporting its concentration, as well as the effects of stirring, particle size, temperature, and type of solute on how fast a solid dissolves in water. While learning about solutions, you also had the chance to gather information and gain new knowledge through the process of conducting science investigations. You also learned the importance of identifying the variables that had to be controlled in order to make a good plan for measuring and testing the variables you are concerned about. What you have started doing in these investigations is what scientists usually do when they seek answers to a scientific question or problem. In the next modules, you will be challenged to ask more questions about materials around you. You will try to explain answers to your hypothesis (your suggested explanation) after you have done your investigation.
References and Links Brady, J.E. & Senese, F. (2004). Chemistry: Matter and its changes, 4th edition. River Street Hoboken, NJ: John Wiley & Sons, Inc. Bucat, R.B. (Ed.) (1984). Elements of chemistry: Earth, air, fire & water, Volume 2. Canberra City, A.C.T., Australia. Elvins, C., Jones, D., Lukins, N., Miskin, J., Ross, B., & Sanders, R. (1990). Chemistry one: Materials, chemistry in everyday life. Port Melbourne, Australia: Heinemann Educational Australia. Hill, J.W. & Kolb, D.K. (1998). Chemistry for changing times, 8th edition.Upper Saddle River, NJ: Prentice Hall. Kurtus, Ron (13 January 2006). Mixtures. Retrieved Jan 9, 2012 from http://www.school-for-champions.com/chemistry/mixtures.htm Philippines. Department of Education. (2004).Chemistry: Science technology textbook for 3rd year. (Revised ed.). Quezon City: Author.
15
and
Suggested time allotment: 5 to 6 hours
Unit 1 MODULE
2
SUBSTANCES AND MIXTURES
Many things around you are mixtures. Some are solid like brass and rocks, or liquid like seawater and fruit juices, or gas like air. Mixtures contain two or more components. These components may vary in size. The variation in size may tell whether a mixture is homogeneous or heterogeneous. In Module 1, you learned about solutions — homogeneous mixtures. They have a uniform composition. This makes the appearance of the mixture the same all throughout. Thus, the components of a solution are difficult to distinguish by the unaided eye. In this module, you will learn other examples of homogeneous mixtures. You will use these samples to differentiate them from substances. How are mixtures different from substances? How are they similar?
Separating Components of a Mixture In the earlier grades, you experienced separating the components of a mixture. You have done this in varied ways. Try to recall some. What are the separation techniques do you remember? Were you also able to recall distillation and evaporation? Different separation techniques make components of a homogeneous mixture more distinguishable, that is, those “unseen” components when they are in a solution become “seen”. Just like in the activity below, distillation and evaporation will help you “see” the two major components of seawater — water and salt.
16
Activity 1 Seawater! See water and salts! Part A Objective In this part, you should be able to collect distilled water and salts from seawater.
Materials Needed
seawater Erlenmeyer flask (sample flask) test tube (receiver) glass tube bent at right angle, with rubber/cork attachment (delivery tube) water bath small boiling chips metal tongs spoon
alcohol lamp tripod safety matches wire gauze (asbestos scraped off) evaporating dish (or aluminum foil) hand lens
Delivery tube
Procedure 1.
Prepare a distillation setup as shown in Figure 1. Place about 60 mL of seawater in the sample flask. Add 23 small boiling chips.
TAKE CARE!
Sample flask
Receiver
Water bath
Handle properly the glassware and flammable materials.
Figure 1. Simple distillation setup 2.
Apply heat to the sample flask until you have collected about 15 mL of the distilled water (distillate). Note: Make sure the source of heat is not removed while the distillation is in progress.
17
3.
Set the rest of the distillate aside. You will use it in Activity 2. Label it properly.
4.
While allowing the remaining seawater to cool, prepare an evaporation setup as shown in Figure 2.
5.
Transfer the cooled liquid to the evaporating dish. Aluminum foil may be used as an alternative for evaporating dish. Note that the aluminum foil was shaped like a bowl so it can hold the sample.
6.
Water bath
Top view of the improvised evaporating dish using aluminum foil
Figure 2. Evaporation using a water bath
Apply heat to the seawater until all the liquid has evaporated. Let it cool. Using a hand lens, examine what is left in the evaporating dish.
Q1. What do you see? Did you notice the solid that was left after all the liquid has evaporated?
7.
TAKE CARE!
The evaporating dish may still be too hot to hold. Use metal tongs.
The solid that is left behind in the evaporating dish is called the residue. Set aside this residue for part B.
Part B Objective In this part, you should be able to compare the residue collected from Part A with table salt using flame test.
Materials Needed
residue collected from Part A denatured alcohol aluminum cooking foil table salt spatula or coffee stirrer match safety eyewear (e.g., goggles, eyeglasses)
18
Procedure 1. Preparation of aluminum boxes. Cut 5x5 cm aluminum cooking foil. Fold the edges of the aluminum foil to form a box as shown in Figure 3. Make at least 6 boxes.
2. In one aluminum box, place a small amount of table salt. In another aluminum box, place a small amount of the residue from Part A. Take another aluminum box and leave it empty.
Figure 3. Aluminum Box
TAKE CARE!
Always wear your safety eyewear while doing the activity. Handle properly the glassware and flammable materials.
3. Add approximately 1mL of denatured alcohol to each box. Light the alcohol and observe the color of the flame produced. Record this color in Table 1. Compare the intensity of the flame colors.
Table 1. Color of the flame of the different samples. Sample
Color
No sample Table salt Residue from Part A
Q2. How does the color of the flame of the residue compare with that of table salt? What can you say about the identity of the residue from Part A?
Distinguishing Substances and Mixtures Seawater is a solution of many different solids, including table salt, in water. Since the solids are dissolved in water, decantation or filtration will not work in separating water from the dissolved solids. Other separation techniques are needed.
19
In the activity above, you were able to separate the components of seawater through distillation and evaporation. One of these is distilled water. It is considered as a substance. But what makes distilled water a substance? In the next activity, you will observe how a substance behaves while it is being boiled or melted. You will also find out that these behaviors will help you differentiate substances from mixtures. Moreover, some mixtures like substances are homogeneous. Given two unlabeled samples, one with water (a substance), and the other a mixture of salt in water; you would not be able to distinguish one from the other just by looking at them.
Activity 2 Looks may be deceiving Part A Objectives In this activity, you should be able to: 1. 2. 3. 4.
assemble properly the setup for boiling (see Figure 4); describe the change in temperature of a substance during boiling; describe the change in temperature of a mixture during boiling; and differentiate between substances and mixtures based on how temperature changes during boiling.
Materials Needed
distilled water seawater beaker (50-mL), 2 pcs aluminium foil, 2 pcs thermometer (with readings up to 110oC)
cork/rubber to fit thermometer iron stand/clamp alcohol lamp safety matches watch/timer graphing paper
Procedure 1.
Place about 15 mL of distilled water into a beaker. Label it properly. Describe the appearance and odor of your sample. In your worksheet, write your descriptions in Table 2.
20
TAKE CARE!
Handle properly the glassware and flammable materials.
2.
3.
Cover the mouth of the beaker with aluminum foil. Using the tip of your pen, poke a hole at the center of the foil. The hole should be big enough for the thermometer to pass through.
Thermometer
Prepare the setup as shown in Figure 4. Notes: Make sure that the thermometer bulb is just above the surface of the sample (about 1 mm). Also, make sure that the heat is evenly distributed at the bottom of the beaker.
4.
Begin recording the temperature when the sample starts to boil vigorously. Record your temperature reading in Table 2 under the column, Distilled water.
Sample in beaker
Figure 4. Setup for boiling
5.
Continue boiling and take at least 5 readings at intervals of 30 seconds after the liquid has started to boil vigorously. Note even the slight changes in temperature. Record your temperature readings in Table 2 under the column, Distilled water.
6.
Stop heating when the liquid sample reaches half of its original volume.
7.
Present your data for distilled water in a graph. Place the temperature reading along the y-axis and the time along the x-axis. Label the graphs appropriately.
Q1. Refer to the graph and your data for distilled water, what do you notice about its temperature during boiling? Q2. How would you define a substance based on what you have observed?
8.
Repeat steps 1 to 7 using seawater. This time, record your temperature readings in Table 2 under the column, Seawater. Note even the slight changes in temperature.
TAKE CARE!
Make sure that the beaker is cool enough to hold. Use another beaker for seawater. Rinse the thermometer and wipe dry before using it to test other samples.
Q3. Refer to the graph and your data for seawater, what do you notice about its temperature during boiling? Q4. How would you define a mixture based on what you have observed?
21
Table 2. Temperature readings of the liquid samples during boiling at 30-sec interval Distilled Water
Seawater
Appearance/Odor Temperature (oC) at start of boiling 30 sec 60 sec Temperature (oC) after
90 sec 120 sec 150 sec
Part B Objectives In this activity, you should be able to: 1. 2. 3. 4.
assemble properly the setup for melting (see Figure 6); describe the appearance of a substance while it is melting; describe the appearance of a mixture while it is melting; and differentiate between substances and mixtures based on how they appear as they melt.
Materials Needed
benzoic acid benzoic acid-salt mixture ballpen cap/coffee stirrer alcohol lamp tripod wire gauze safety matches
22
watch/timer cover of an ice cream can (about 7-8 cm diameter) paper scissors/cutter marker pen
Procedure 1.
Construction of an improvised melting dish from a cover of an ice cream can. This may be prepared ahead. a)
Trace the outline of the cover of an ice cream can on a piece of paper. Cut the paper following the outline. Adjust the cut-out so it fits well in the inner part of the ice cream can cover. See Figure 5a.
b)
Fold the cut-out into 4 equal parts. Place the folded cut-out on top of the cover (inner part) of the ice cream can. See Figure 5b.
c)
Following the crease of the paper, trace lines using a marker pen into the cover. Remove the cut-out. See Figure 5c.
d)
In each radius, locate points which are equidistant from the center. Using the tip of a cutter, etch and mark these points as X 1, X2, X3, and X4. See Figure 6.
5a
5b
5c
Figure 5. Guide in constructing an improvised melting dish
Your improvised melting dish should look similar as Figure 6. Samples will be placed at the X marks. This melting dish may hold as much as 4 samples at one time. Figure 6. Improvised melting dish
2.
Prepare the setup as shown in Figure 7.
23
TAKE CARE!
Handle properly flammable materials.
Figure 7. Setup for melting
3.
Using the tip of a ballpen cap, place about a scoop of benzoic acid in X1 and benzoic acid-salt mixture in X4 marks of the improvised melting dish. Do not put anything in the X2 and X3 marks. Note: The figure below illustrates how much one scoop of sample is.
Scoop of sample
Figure 8. Ballpen cap as improvised spatula with a scoop of sample
4.
Examine each sample. Describe the appearance. In your worksheet, write your descriptions for the two samples in Table 3.
5.
Make sure that each sample receives the same amount of heat. Observe each sample as they melt.
24
TAKE CARE!
Do not inhale the fumes/ vapor.
Table 3. Appearance of the solid samples
Benzoic acid (X1)
Benzoic acid-Salt mixture (X4)
Appearance
Q1. What did you observe while benzoic acid is melting? Q2. How would you define a substance based on what you have observed? Q3. What did you observe while benzoic acid-salt mixture is melting? Q4. How would you define a mixture based on what you have observed?
The salt that you recovered in Activity 1 is mainly sodium chloride. It melts at 801 C. Imagine how hot that is! It is about 700oC higher than the boiling point of water. Because of this and limited equipment, it will be difficult to perform this in a school laboratory. However, given that sodium chloride is a substance, what could be the expected observation as it melts? o
In the next activity, you will apply what you have learned from this module in classifying unknown samples. This time, you have to decide which setup fits best with the sample you are given. You have to work out a procedure to identify if the sample is a substance or a mixture. Try to design the procedure first by recalling what you have done in the previous activities. Let these activities serve as guides which you can check side by side with your design. Take note of safety measures and wait for your teacher to give you the “go signal” before proceeding.
Activity 3 My unknown sample: Substance or mixture? Objective In this activity, you should be able to design a procedure that will identify unknown samples as mixtures or substances.
25
Materials Needed
unknown sample
Procedure 1.
Design a procedure to identify if the unknown sample is a mixture or a substance. Limit the materials that you are going to use with what is already available.
2.
Perform the activity that you designed after your teacher has checked your procedure.
Q1. What is your basis in identifying the unknown sample you have?
There are mixtures that are homogeneous which may be mistaken as substances. Being so, appearance may not be the best basis to differentiate substances from mixtures. However, there are ways to tell by noting how a sample behaves during boiling and melting. In the higher grade levels, you will learn why this is so.
During boiling, the temperature of a substance changes at the start then it becomes the same; while the temperature of a mixture is different at different times. During melting, a substance melts completely/smoothly within a short time; while a mixture has portions that seem to be not melting.
In the next module, you will learn more about substances. Collect as many product labels as you can, you will refer to them as you identify and classify the substances present in the product.
26
Suggested time allotment: 5 to 6 hours
Unit 1 MODULE
3
ELEMENTS AND COMPOUNDS
All substances are homogeneous. Some mixtures are also homogeneous, particularly solutions. Being so, it is difficult to distinguish mixtures and substances based on appearance. However, there are ways to tell if a sample is a mixture or a substance. The temperature of a liquid mixture varies during boiling but for a liquid substance, it does not. A solid mixture has portions that do not melt but a solid substance melts completely within a short time. In this module, you will find out that substances may be further classified into two: compounds and elements. You will start with the primary characteristic that distinguishes them. How are elements different from compounds? How are they similar?
Compounds Like mixtures, compounds are also made up of two or more components. In Module 2, you separated the components of seawater through distillation. One of the
27
products obtained was distilled water. Also, you have identified distilled water as a substance. In the activity that you are about to do, you will again “see” for yourself components, but this time, “what water is made of”. With the passage of electric current, components of water may be separated from each other. This process is called electrolysis. You will use an improvised electrolysis apparatus like the one shown in the figure below. Commonly available materials were used to construct this improvised apparatus.
sample container
1
1
2
2
3 4 5 6 7 8
3 4 5 6 7 8
9
9
10 11
10 11
electrolysis syringe
stainless screw
Connect red wire to positive (+) terminal of the dry cell.
Connect black wire to negative (-) terminal of the dry cell.
Figure 1. An improvised electrolysis apparatus
Activity 1 Water, “wat-er” you made of? Objectives In this activity, you should be able to: 1. 2.
carry out the electrolysis of water; and identify the components of water.
28
Materials Needed
TAKE
Be careful in handling the sodium hydroxide.
improvised electrolysis apparatus CARE! 5% sodium hydroxide (NaOH) solution connecting wires (black and red insulation) 9V dry cell test tube plastic syringes will serve as “collecting syringe” incense or bamboo stick safety matches
Procedure 1.
Fill the sample container of the electrolysis apparatus half-full with 5% sodium hydroxide (NaOH) solution.
2.
Fill each “electrolysis syringe” with 5% sodium hydroxide (NaOH) solution up to the zero mark. To do this, insert the tip of the “collecting syringe” through the hole of the plastic straw and suck out the air. Refer to Figure 2. Initially, the plunger of the “collecting syringe” should be in the zero position. The 5% sodium hydroxide (NaOH) solution will rise and fill the “electrolysis syringe” as you pull the plunger of the “collecting syringe”.
3.
Figure 2. Filling up the “electrolysis syringe” with the sample
When the solution reaches the zero mark, fold the straw with the “collecting syringe”. Refer to the figure on the right. Repeat the procedure for the other syringe. Note: In case the 10mL syringe is used for sucking out the air, you may need to repeat the suction of air to fill up the “electrolysis syringe” with the 5% sodium hydroxide (NaOH) solution.
4.
Attach the connecting wires to the bottom tips of the stainless screws. Attach the black wire to the negative (-) terminal of the dry cell. Attach the red wire to the positive (+) terminal of the dry cell. The stainless screw that is attached to the black wire is the negative electrode; while the stainless screw that is attached to the red wire is the positive electrode.
5.
Once the wires are connected with the dry cell, electrolysis will start. Electrolyze until 6-8 mL of a gas is obtained at the negative electrode.
29
6.
Draw out the gas at the negative electrode with the “collecting syringe”. To do this, insert the tip of the “collecting syringe” into the straw on the side of the negative electrode. See figure on the right. Remove the clip and draw out the gas. Note: The plunger of the “collecting syringe” should be at the zero mark before drawing up the gas. While drawing out the gas, you will notice that the solution will rise up and fill the “electrolysis syringe” again. Make sure that the “collecting syringe” will only contain the gas generated. However, take this chance to refill the “electrolysis syringe” with the solution. When the level of the solution reaches the zero mark in the “electrolysis syringe”, slowly lower down the “collecting syringe” and immediately cover its tip with your finger.
7.
Refer to the figure on the right. Inject the collected gas into an inverted test tube and again cover the mouth of the test tube with your thumb. Immediately test the gas collected with a lighted match or bamboo stick/ incense.
Lighted match
Q1. What happened when you placed a lighted match near the mouth of the test tube?
8.
Continue to electrolyze until 6-8 mL of the gas is obtained at the positive electrode.
9.
Refer to the figure on the right. Draw out the gas from the positive electrode and immediately inject into a test tube held in upright position. Immediately test the gas collected by thrusting a glowing (no flame) bamboo stick all the way down towards the bottom of the test tube. Note: Extinguish any flame from the burning stick but leave it glowing before thrusting it inside the test tube.
Q2. What happened when you thrust a glowing bamboo stick inside the test tube?
30
Glowing bamboo stick
water
Collected gas
Electrolysis decomposed water, a compound, into hydrogen and oxygen. Hydrogen and oxygen are elements. As you have seen from the activity above, compounds are substances that consist of two elements. As you encounter more compounds, you will find out that there are compounds that may be composed of more than two elements. In the activity above, you noted that oxygen, the gas collected in the positive electrode, made the lighted stick burn more vigorously. This means oxygen supports burning. Hydrogen, the gas you collected in the negative electrode, gave a popping sound when a glowing stick was thrust into it. The sound comes from the rapid burning of hydrogen in the presence of air. Note how different the properties are of hydrogen and oxygen from water. Hydrogen burns and oxygen supports burning while water extinguishes fire. Hydrogen is a gas at room temperature; so is oxygen. Water, on the other hand, is a liquid at room temperature. The compound (in this case, water) that is composed of elements (in this case, hydrogen and oxygen) has properties that are distinctly different from the elements. In other words, when elements combine to form compound, a different substance is formed. In the higher grade levels, you will learn how this combination of elements happens.
Elements Each element has different set of properties. No two elements have the same set of properties. Just like the two elements that were generated in Activity 1 — hydrogen and oxygen. Even though they are both in gaseous state at room temperature, they behave differently when exposed to a flame or spark of flame. Hydrogen gives off a “pop” sound when ignited; while oxygen induces a brighter spark. This difference in behavior implies a difference in property. In effect, hydrogen and oxygen are different substances, or to be more specific, they are different elements. There are quite a number of elements known in the current time. Thanks to the works of our early scientists, they were able to systematically organize all of these elements in what we call the periodic table of elements or sometimes simply referred as periodic table. You will find one at the back page of this module. Amazingly, they were able to logically arrange the elements in the table enabling one to have an idea of the properties of several elements by knowing other elements related to them. This means that there is no need to memorize the periodic table but it is an advantage to be familiar with it. Thus, in the next activity, you will accustom yourself with the periodic table.
31
Activity 2 The periodic table: It’s element-ary! Objectives In this activity, you should be able to: 1. be familiar with the layout of the periodic table; 2. know some information about the elements that may be found in the periodic table; and 3. identify the group number an element it belongs to.
Material Needed
periodic table of elements
Procedure 1.
2.
Every element has a name. In each box of the table, you will find only one name. One box corresponds to one element. Using the partial figure of the periodic table on the right, find where oxygen is. For the next questions, please refer to the periodic table of the elements found at the end of Unit 1. Write your answers for each question in Table 1.
a.
Scientists agreed to give symbols for each element. This is very helpful especially to those elements with long names. Instead of writing the full names, a one-letter or two-letter symbol may be used. You can find these symbols in the periodic table too. It is written inside the same box for that element. For instance, O is the symbol for oxygen.
Q1. What are the symbols for elements with long names such as beryllium, phosphorus, germanium, and darmstatdtium?
32
Table 1. Name and symbol of some elements and the group number it belongs to. Name
Symbol
Group Number
Note: Please add rows as necessary
b.
Notice that most of the one-letter symbols are the first letters of these elements.
Q2. What are the symbols for boron, nitrogen, fluorine and vanadium?
c.
For the two-letter symbols, most of them start with the first letter of the element. Notice that the second letter in the symbol may be any letter found in the element’s name. Notice as well that only the first letter is capitalized for the two-letter symbols.
Q3. What are the symbols for lithium, chlorine, argon, calcium and manganese?
d.
There are symbols that use letters that were taken from the ancient name of the element. Examples of ancient names are ferrum (iron), argentum (silver), hydrargyrum (mercury) and plumbum (lead).
Q4. What are the symbols for iron, silver, mercury, and lead?
e.
In the earlier grade levels, you already encountered elements. You studied rocks and learned that some are composed of silicon and magnesium. Some even have gold.
Q5. What are the symbols for silicon, magnesium and gold?
f.
When you were recycling materials, you segregated the objects according to what these are made of. Some of them are made from aluminum, copper, tin or carbon.
Q6. What are the symbols for these 4 elements?
g.
In nutrition, you were advised to eat enough bananas because it is a good source of potassium.
Q7. What is the symbol for potassium?
h.
In each box, you will find a number on top of each symbol. This is the atomic number. In the higher grade levels, you will learn what this number
33
represents. For now, use it as a guide on how the elements are sequenced. Q8. What is the element’s name and symbol that comes before titanium? How about that comes after barium?
i.
Elements that are in the same column have similar properties. For this, each column is called a family and has a family name. However, at this point, you will refer first to each family with their corresponding group number. Notice that the columns are numbered 1 to 18 from left to right.
Q9. In which group does each of the elements listed in Table 1 belongs to?
There are many elements present in the food you eat —whether it is raw like banana or those processed like banana chips, biscuits, milk, and juice. These are mostly nutrients which the human body needs in order to function well. Some of these are calcium, magnesium, zinc, and selenium. Find these elements in the periodic table. Can you name more? Did you also find them in the periodic table? In the next activity, you will find out how these elements are present in the food you eat. From the product labels, information about the contents of the food is written — named as Nutrition Facts and Ingredients. The Nutrition Facts is a list of the different nutrients provided by the food product with their corresponding percentage share on the daily recommended dietary allowance. Refer to the figure on the right. Notice that some of these nutrients are elements such as calcium. Is this food a good source of calcium?
On the other hand, Ingredients give you a list of the materials that have been added to make the food product. These materials are the sources of the nutrients. These are the ones that are taken in by the body. Refer to the figure below. Find the ingredient ferrous sulphate (FeSO4). Ferrous is derived from the Latin name of iron. Refer to the figure on the right. This is the Nutrition Facts which corresponds to the
34
food product having these ingredients. Find the nutrient iron. How much iron does this food product give as part of the recommended dietary allowance? From this product label, you can tell that you will be getting as much as 35% of iron that you need for the day and you will get it as ferrous sulfate — a compound of iron.
Activity 3 The “matter” on labels Objectives In this activity, you should be able to: 1. 2. 3. 4.
name elements that are listed in the Nutrition Facts of a food label; recognize that the elements listed in the Nutrition Facts are not added as the elements themselves; infer the food ingredient that could be the source of those listed elements; and recognize that most of these food ingredients are examples of compounds.
Materials Needed
food labels
Procedure 1.
Refer to the labels of different food products below.
Ingredients: sucrose, creamer (glucose syrup, hydrogenated palm kernel oil, sodium caseinate containing milk, sequestrants, emulsifiers, nature-identical flavors, sodium chloride, anticaking agents), maltodextrin, cereal flakes (wheat flour, rice flour, malt extract, sucrose, corn grits, acidity regulator), sweet whey powder, cocoa powder, iodized salt, thickener, artificial flavour, zinc sulfate, iron pyrophosphate. May contain traces of soya.
Cereal drink
35
Chocolate candy
INGREDIENTS: SUGAR, GLUCOSE SYRUP, MILK NGREDIENTS, MODIFIED PALM OIL, UNSWEETENED CHOCOLATE, MODIFIED VEGETABLE OIL, PALM OIL, VEGETABLE OIL, COCOA BUTTER, SALT CALCIUM CHLORIDE, CITRIC ACID, SODIUM BICARBONATE, SOY LECITHIN, NATURAL AND ARTIFICIAL FLAVORS. MAY CONTAIN PEANUTS, TREE NUTS OR EGG.
Ingredients: water, hydrolysed soybean protein, iodized salt, sugar, natural and artificial colors with tartrazine, acidulant, monosodium glutamate, 0.1% potassium sorbate, natural flavor and flavor enhancer.
Soy sauce
36
2.
List down in Table 2 the compounds in the product label and the constituent elements. There are cases that you will need to look up the constituent elements because they may not be obvious from the compound name (e.g., citric acid, oil).
Table 2. Compounds and their constituent elements written in the food labels Food Product
Compound
Constituent Element
Cereal Drink Chocolate candy Soy sauce Note: Please add rows as necessary
3.
The elements iron and zinc are listed in the Nutrition Facts for the cereal drink. Find out from the Ingredients the source of these elements.
4.
Name three elements present in the Ingredients of the cereal drink which are not listed in the Nutrition Facts.
As you have learned from the activity above, the elements in food are in combination with other elements and the resulting compounds are referred to as minerals. Thus, you are not eating the elements themselves. A product label that lists sodium as a nutrient means that the composition of one of the ingredients includes sodium. In the case of soy sauce, one possible ingredient is monosodium glutamate. It is very rare and most of the time dangerous if you take in the element itself. In Activity 1, you have seen that water did not give off a “pop” sound nor induced a bright spark when exposed to a spark or flame, unlike its constituent elements hydrogen and oxygen, respectively. This means that the properties of compounds are different from the properties of the elements it is made up of. There are cases that the properties of a compound pose less risk than its constituent elements. An example is sodium and one of its compounds. Sodium is an element that burns Photo credits: http://www.visualphotos.com/image/1x7465368/sodium_reacting_ when it comes in contact with water. Refer to the with_water_chemical_reaction photo above. Imagine the danger that you are in to if you will be eating sodium as an element. However, sodium chloride, which is a compound made up of the elements sodium and chlorine, does not burn when it comes in contact with water. In fact, sodium chloride is sometimes used with water
37
as common food ingredient. Perhaps, you are already familiar with this. Does table salt ring a bell? Sodium chloride is commonly called as table salt. As you know, it is safe to eat. Do take note though that it should be consumed in the right amount. Excessive consumption of sodium chloride may lead to kidney failure. This stresses the importance of reading product labels. This will let you know how much of a nutrient you get from a food product. Refer to Figure 3. How much calcium do you need to consume in a day? How about magnesium? Avoid taking them beyond these recommended amounts. It may lead to sickness, and even death. It is imperative that you are aware of what makes up the food that you are eating. You may also refer to Table 3 on the next page for food sources of some minerals when preparing your meal.
Figure 3. Recommended mineral intake (WHO, 2004) 38
Table 3. Some elements essential to life* Element Macrominerals
Source
Deficiency condition Rickets in children; diseases of the bones in adults such as softening of the bones and decrease in bone mass
Zinc (Zn)
Essential to formation and maintenance of bones and teeth; regulates nerve transmission, muscle contraction, and blood clotting Catalyst in the synthesis of energy-carrier molecules; involved in the synthesis of proteins and relaxation of muscles Maintains regular heartbeat, water balance and cell integrity; needed in nerve transmission, carbohydrate and protein metabolism Part of enzymes; antioxidant Regulates amount of body fluid; involved in nerve transmission Component of biomolecules and ions Part of insulin and some 154 enzymes
Loss of insulin efficiency with age Rare
Fluorine (F)
Needed for glucose utilization Helps in the formation of hemoglobin; part of 11 enzymes Strengthens bone and tooth structure Component of hemoglobin and myoglobin
Anemia, tiredness, and apathy
Part of thyroxin, regulates rate of energy use Cofactor for a number of enzymes
Goiter
Calcium (Ca)
Magnesium (Mg)
Potassium (K)
Selenium (Se) Sodium (Na) Sulfur (S)
Milk, cheese, canned fish with bones, sesame seeds, green leafy vegetables
Function
Nuts, legumes, cereal grains, dark green vegetables, sea food, chocolate Orange juice, bananas, dried fruits, potatoes
Liver, meat, grain, vegetables Meat, table salt, salt- processed food Some proteins
Liver, shellfish, meat, wheat germs, legumes Microminerals or Trace elements Liver; animal and Chromium (Cr) plant tissues Liver, kidney, egg Copper (Cu) yolk, whole grains
Iron (Fe)
Iodine (I) Manganese (Mn)
Sea food, fluorinated drinking water Liver, meat, green leafy vegetables, whole grains, cocoa beans Sea food, iodized salts Liver, kidney, wheat germ, legumes, nuts
*Source: Chemistry S&T Textbook for Third Year, 2009
39
Fluid loss due to too much alcohol intake; heart failure due to spasms Sudden death during fasting, poor nerve function, irregular heart beat
Keshan disease (heart disease) Headache, physical weakness, thirst, poor memory, appetite loss
Anemia, stunted growth
Dental decay
Weight loss, occasional dermatitis
It is also an advantage if you know the different names of the elements and compounds. Take the case of the food product label below. Refer to the Nutrition Facts of the cereal product on the right. It tells that this cereal product provides the nutrient, sodium. Now, refer to the Ingredients. Do you find any ingredient that could be a source of sodium? It may seem not, at first. However, knowing that the other name for sodium chloride is salt, you can now identify one source ingredient for the sodium that is listed in the Nutrition Facts. Note that there are instances that the Nutrition Facts is incomplete. You may find an element unlisted but once you check the Ingredients, you can tell that the food product could be a source of that element. Refer to the label of the cereal drink you used in Activity 3. Is sodium listed in the Nutrition Facts? Is there an ingredient that could be a source of sodium? When you read product labels, make sure you do not miss out on these information. This will help you decide if the product is worth buying. Any ingredient added to food should be safe to eat in terms of quality and quantity. By quality, these ingredients must be food grade. A substance undergoes a process before it becomes food grade. It is only after that, a substance may be safely added as a food ingredient. If it is a non-food grade substance then it should not be added to products that are meant to be ingested. Refer to the product labels for a soy sauce and a lotion. Notice that potassium sorbate is a common ingredient. It has the same function for both products, that is, it acts as a preservative so the product would last longer. However, it is important to note that food grade potassium sorbate was added in soy sauce; while a non-food grade potassium sorbate may be added in the lotion. Notice that the product label does not indicate if the ingredient is food grade or not. However, there are government agencies that make sure the food products that are sold in the market uses only food grade ingredients.
40
In the next activity, you will encounter another substance that is common to materials that are not meant to be ingested. However, this substance was made food grade before it was added as a food ingredient. This substance is iron. This food grade iron is sprayed onto the food or added as a powder to the mixture. Because it is the elemental iron that was added as a mixture, its properties are retained. One of these is its magnetic property. Thus, you can recover the iron present in the food product by using a magnet.
Activity 4 The iron-y of food fortification Objective: In this activity, you should be able to recover iron from a food product. Materials Needed
processed food product rich in reduced iron magnetic stirrer (magnet with white coating) blender water beaker measuring cup forceps
Procedure 1.
Place one cup of the food sample in a blender. Add one cup of water.
2.
Transfer the crushed sample to a beaker. If the mixture is too thick, add more water.
3.
Make sure that the magnetic stirring bar is clean. Place it in the beaker containing the mixture.
4.
Stir the mixture for about 15 minutes in a magnetic stirrer.
TAKE CARE!
Do not eat the food samples and the iron that will be extracted in the activity.
Note: If the magnet does not seem to move, the mixture might still be thick. If this happens, add enough water.
5.
Using the forceps, retrieve the magnetic stirring bar from the mixture. Take a closer look at the magnetic stirring bar.
Q1. Do you notice anything that clings to the magnetic stirring bar?
41
6.
Let the magnetic stirring bar dry. Scrape off whatever has clung to it. Bring a magnet close to the dried material. Observe what happens.
Q2. What can you infer about the identity of the dried material? What made you say so?
As you have seen, elements are part of almost anything around us — food, clothes, rocks, and even this paper you are currently reading from. Elements are said to be the building blocks of matter. They are like blocks that you can put together and build something new. When you build something new from these elements, you call them as compounds.
Compounds are made up of elements. Elements are the simplest form of matter. Both elements and compounds are substances.
With the 118 elements, imagine how many combinations of elements you can make into compounds and how diverse the materials around us can be. In Modules 4 and 5, you will learn more about the compounds and elements. You will work on different samples of compounds and elements and explore their properties.
42
Suggested time allotment: 5 to 6 hours
Unit 1 MODULE
4
ACIDS AND BASES
In Module 1, you identified common properties of solutions using different methods. You learned how to report the amount of the components in a given volume of solution. You also found out that not all solutions are liquid. Some of them are solids and others are gases. Towards the end of the module, you investigated the factors that affect how fast a solid dissolves in water. In Module 3 you learned about compounds. In Module 4 you will study two special and important classes of compounds called acids and bases. Examples of acids are acetic acid in vinegar and citric acid in fruit juices. The solution used for cleaning toilet bowls and tiles is 10-12% hydrochloric acid. It is commonly called muriatic acid. These acids in these mixtures make the mixtures acidic. We can say the same about bases and basic solutions. An example of a base is sodium hydroxide used in making soaps and drain cleaners. Sodium hydroxide is also called lye or caustic soda. A common drain cleaner used in most homes in the Philippines is called sosa. Another base is aluminum hydroxide used in antacids. The bases in these mixtures make the mixtures basic. In this module you will investigate the properties of acidic and basic mixtures using an indicator, a dye that changes into a specific color depending on whether it is placed in an acidic solution or in a basic one. Aside from knowing the uses of acidic and basic mixtures, you will also find out the action of acid on metals and think of ways to reduce the harmful effects of acids. Knowing the properties of acids and bases will help you practice safety in handling them, not only in this grade level, but in your future science classes.
How acidic or basic are common household materials? Does water from different sources have the same acidity? What is the effect of acid on metals?
43
Activity 1 How can you tell if a mixture is acidic or basic? How will you know if a mixture is acidic or a basic? In this activity, you will distinguish between acidic and basic mixtures based on their color reactions to an indicator. An indicator is a dye that changes into a different color depending on whether it is in acid or in base. There are many indicators that come from plant sources. Each indicator dye has one color in an acidic mixture and a different color in a basic mixture. A common indicator is litmus, a dye taken from the lichen plant. Litmus turns red in acidic mixtures and becomes blue in basic mixtures. You will first make your own acid-base indicator from plant indicators available in your place. This is a colorful activity. You may select a local plant in your community. You can use any of the following: violet eggplant peel, purple camote peel, red mayana leaves or violet Baston ni San Jose. These plant materials contain anthocyanins. These plant pigments produce specific colors in solutions of different acidity or basicity. In this activity, you will: 1. Prepare a plant indicator from any of the following plants: violet eggplant peel, purple camote peel, red mayana leaves or violet Baston ni San Jose; and 2. Find out if a given sample is acidic or basic using the plant indicator.
TAKE CARE!
It is dangerous to taste or touch a solution in order to decide if it is acidic or a basic.
Part A. Preparation of Indicator* In this part of Activity 1, you will prepare a plant indicator that you will use to determine if a given sample is acidic or a basic.
Materials Needed
1 pc mature, dark violet eggplant or camote leaves of Mayana or Baston ni San Jose alum (tawas) powder
*University of the Philippines. National Institute for Science and Mathematics Education Development (2001). Practical work in high school chemistry: Activities for students. Quezon City: Author, pp. 29-33.
44
sharp knife or peeler small casserole or milk can brown bottle with cover alcohol lamp tripod
Procedure 1.
Peel an eggplant as thin as possible. (You may also use the skin of purple camote or the leaves of red mayana or Baston ni San Jose.) Cut the materials into small pieces and place in a small casserole or milk can. You may keep the flesh of the eggplant or camote for other purposes.
2.
Add about ⅓ to ½ cup tap water to the peel depending on the size of the eggplant or camote used. Boil for 5 minutes. Stir from time to time.
3.
Transfer the mixture into a bottle while it is still hot. There is no need to filter, just remove the solid portion. The mixture may change if left in open air for more than 5 minutes.
4.
Immediately add a pinch (2-3 matchstick head size) of alum (tawas) powder into the solution or until the solution becomes dark blue in color. Stir well while still hot. This is now the indicator solution.
Note: Alum will stabilize the extract. The extract will be more stable with alum but it is recommended that the solution be used within a few days. Keep the extract in the refrigerator or cool dark place when not in use. Part B. Determining the acidity or basicity of some common household items In this part of the activity, you will find out if a given household material is acidic or basic using the plant indicator you have prepared in Part A.
Materials Needed
plant indicator prepared in Part A vinegar distilled water tap water baking soda baking powder calamansi
45
Other food/home items with no color: (toothpaste, shampoo, soap, detergent, fruit juice like buko juice, sugar in water, soft drink) 2 plastic egg trays or 12 small plastic cups or glass bottles 6 droppers 6 plastic teaspoons stirrer (may be teaspoon, barbecue stick or drinking straw)
Procedure 1.
Place one (1) teaspoon of each sample in each well of the egg tray.
2.
Add 8-10 drops (or ½ teaspoon) of the plant indicator to the first sample.
Note: If the sample is solid, wet a pinch (size of 2-3 match heads) of the solid with about ½ teaspoon of distilled water.
TAKE CARE!
3.
Use one dropper for one kind of sample. Wash each dropper after one use. Do not mix samples!
Note the color produced. Record your observations in column 2 of Table 1.
Table 1. Acidic or basic nature of household materials Sample calamansi tap water (water from the faucet) distilled water vinegar sugar in water baking soda baking powder soft drink (colorless) coconut water (from buko) toothpaste shampoo soap
4.
Color of indicator
Repeat step number 1 of Part B for the other samples.
46
Nature of sample
5.
Determine the acidic or basic nature of your sample using the color scheme below for eggplant or camote indicator and record the nature of each sample in Table 1. Strongly acidic: red to pale red Weakly acidic: blue Weakly basic: green Strongly basic: yellow
Part C. Determining the acidity or basicity of water from different sources In this part of Activity 1, you will find out how acidic or basic the samples of water from different sources are.
Materials Needed At least one cup water from each of the following sources of water:
plant indicator prepared in Part A rainwater river, lake or stream pond canal faucet deep well or hand pump bottled water (mineral water) or distilled water 2 plastic egg trays or 8 small plastic containers 6 droppers 6 plastic teaspoons
Procedure 1.
Place one (1) teaspoon of each sample in each well of the egg tray.
2.
Add 8-10 drops (or ½ teaspoon) of the plant indicator to the first sample.
Note: If the sample is solid, wet a pinch (size of 2-3 match heads) of the solid with about ½ teaspoon of distilled water.
TAKE CARE!
Use one dropper for one kind of sample. Wash each dropper after one use. Do not mix samples!
47
3.
Note the color produced. Record your observations in column 2 of Table 2.
Table 2. Acidic or basic nature of water from different sources Water sample from source
Color of indicator
Nature of sample
rainwater river, lake or stream Pond Canal water from faucet 4.
Determine the acidic or basic nature of your sample using the color scheme below for eggplant or camote indicator and record the nature of each sample in Table 2. Strongly acidic: red to pale red Weakly acidic: blue Weakly basic: green Strongly basic: yellow
You can now operationally distinguish between acidic and basic mixtures using plant indicators. More than that, using the plant extract you have prepared allowed you to further determine the degree of acidity or basicity of a mixture, that is, you were able to find out how strongly acidic or basic the mixtures were. Another method can be used to indicate the acidity or basicity of mixtures. It is through the use of the pH scale, which extends from 0 to 14. The pH scale was proposed by the Danish biochemist S.P.L. Sorensen. In this scale, a sample with pH 7 is neutral. An acidic mixture has a pH that is less than 7. A basic mixture has a pH that is greater than 7. In general, the lower the pH, the more acidic the mixture and the higher the pH, the more basic is the mixture. It is useful for you to know the pH of some samples of matter as shown in Table 3 and illustrated in the pH scale drawn in Figure 1.
48
Table 3. Approximate pH values of some samples of matter Sample of Matter Gastric juice Lemon juice Vinegar Soft drinks Urine Rainwater (unpolluted) Milk Saliva Pure water Blood Fresh egg white Seawater Laundry detergents Household bleach Drain cleaner
pH 1.6-1.8 2.1-2.3 2.4-3.4 2.0-4.0 5.5-7.0 5.6 6.3-6.6 6.2-7.4 7.0 7.35-7.45 7.6-8.0 8.4 11 12.8 13.0
Figure 1. The pH values of some samples of matter.
49
Activity 2 Color range, pH scale! In this activity, you will use the results in Activity 1, Parts B and C, to determine the pH of the solutions you tested. Use the following pH scale for eggplant indicator to determine the pH of the common mixtures you tested in Activity 1. Present your results in a table similar to Table 4. The eggplant indicator shows the following color changes. pH 1 2 red/
3 4 pale/ red
5
6 blue
ACIDIC
becoming more acidic
7
8 9 10 /green
11 12 13 /yellow
14
BASIC
N E U T R A L
becoming more basic
Table 4. pH of samples from Activity 1 Sample
pH based on eggplant/camote indicator
Acidic or Basic
Now that you are aware of the pH of some common mixtures, why do you think is it important to know about pH? The following facts give you some information on how pH affects processes in the body and in the environment, as well as in some products you often use.
50
Importance of pH pH and the Human Body Acids and bases perform specific functions to balance the pH levels in the body. When your body has too much carbon dioxide, the blood becomes too acidic. You breathe slowly. Breathing is slowed to increase the pH in the blood. If pH in the body is too basic, you will hyperventilate to lower the pH. This acid and base control is an important part of biological homeostasis (balance) in humans. In fact, human life is sustained only if the pH of our blood and body tissues is within a small range near 7.4.
Use of pH in Food Processing and Fruit Preservation During food processing, pH is closely followed. Changes in pH affect the growth of microorganisms, which cause food spoilage. Most bacteria grow best at or near pH 7. To prevent the growth of harmful bacteria, pickling is an effective food preservation method because it lowers pH. The control of pH is also needed in wine and jam preparation. A few species of bacteria grow in a basic medium of pH 9-10. This is the pH range of stale eggs. Most molds grow within the pH range of 2- 8.5. In acidic conditions, many fruits and products made from fruits are easily attacked by molds unless the fruits are properly protected.
Control of pH in Soil The pH of soil is very important. Some plants grow well in acidic soil while others prefer basic soil. Farmers need to know the pH of their soil since plants will only grow in a narrow pH range. The pH also affects how much nutrients from the soil become available to plants. The following useful plants in the Philippines grow in acidic soils: banana, kaimito, durian, pineapple, soybean, coffee, eggplant, squash, kamote, and rice. Other plants like grapes and pechay require basic soils. Some plants grow best in almost neutral soil like orange, peanut, watermelon, beans, cabbage, tomato, corn garlic, and onion.
pH of Rainwater The average pH of rain is 5.6. This slightly acidic pH is due to the presence of carbon dioxide in the air. In many areas of the world, rainwater is much more acidic, sometimes reaching pH 3 or even lower. Rain with a pH below 5.6 is called “acid rain.” The acidic pollutants in the air that come from the burning of fuels used in power plants, factories, and vehicles produce gases which are acidic. These gases enter the atmosphere and dissolve in
51
water vapor in the air. Some acid rain is due to natural pollutants like those from volcanic eruptions and lightning.
Maintaining pH of Personal Care Products Most personal care products have pH kept at specific levels to avoid harmful effects on the body. This is true for hair products. For example, at pH 12, hair already dissolves, that is why hair removers usually have pH of 11.5 to12. Most shampoos are within the pH range of 4 to 6. This is because the pH of the product must be compatible with that of the hair, which is in the range pH 4 to 5. Hair is least swollen and is strongest at this pH range. But very often, using shampoo leaves the hair basic. So, in order to avoid eye irritation and stinging, shampoos for infants and children have a pH similar to that of tears (pH 7.4). Hair has a protective covering called sebum. The use of conditioners after using shampoo puts back this oily coating and penetrates the hair shaft itself. Now that you have discussed with your teacher the importance of keeping the proper pH in the human body, in food processing and food preservation, in farming and in personal care products, it is also essential that you know the effects of acids on some common metals. An important property of acids is their tendency to react with certain metals. At higher grade levels, you will learn that the nature of the metal determines how it is affected by specific types of acid. However, in this grade level, you will simply investigate the effect of an acid on a common metal like iron.
Effect of an Acidic Mixture on Metal What do you think will happen when an acid and a metal come in contact with each other? What happens after the metal has been in contact with the acid for some time? What changes take place? In Activity 3, you will investigate the effect of an acid on a common metal like iron. In Module 1, you have learned that vinegar is about 5% acetic acid. You will be using vinegar in this investigation since it is safe to handle and easily available. Vinegar will simply be an example that can show the action of an acidic solution when it comes in contact with a metal. There are other acids that affect metals but you will learn about them in Grades 8 and 9.
52
Activity 3 What happens to a metal when exposed to an acidic mixture? Objective In this activity, you will find out the effect of an acidic mixture, like vinegar, on iron.
Materials Needed
3 pieces, small iron nails (about 2.5 cm long) 1 cup white vinegar (with 4.5 to 5 % acidity) 3 small, clear bottles or 100 mL beaker 1 cup water 2 droppers
Procedure 1. Prepare a table similar to the one below. Setup
After one day
Observations After 2 days
After 3 days
Iron nail (1) Iron nail (2) Iron nail (3) 2.
Clean and wipe dry all the iron nails and the bottles.
3.
Place one piece of the iron nail in each bottle.
Q1. Why do you think are there three different bottles for each sample of iron nail? 4.
Put two to three drops (just enough to barely cover the sample) of vinegar on top of the iron nail in each bottle.
5.
After adding vinegar to all samples, put aside the bottles where you can observe changes for three days.
6.
Write your observations after one day, two days, and three days on the data table in step #1.
Q2. At the end of three days, describe completely what happened to each sample.
53
Q3. Give explanations for the results you have observed.
You have observed the action of vinegar, an acidic mixture, on metal such as iron in Activity 3. Do you think other types of acidic mixtures act in the same way with other metals? What about other types of materials? You will learn a lot more about the action of acids on metal and on different types of materials in Grades 8 and 9.
Safety in Handling Acids and Bases Now that you know the properties of acidic and basic mixtures, you can handle them carefully. Acids and bases with high concentrations can cause serious burns. For example, hydrochloric acid (commonly called muriatic acid) is used in construction to remove excess mortar from bricks and in the home to remove hardened deposits from toilet bowls. Concentrated solutions of hydrochloric acid (about 38%) cause severe burns, but dilute solutions can be used safely in the home if handled carefully. You can find the following caution in a bottle of muriatic acid:
Harmful or fatal if swallowed. Strong irritant to eye, skin, and mucous membrane. Do not take internally. Avoid contact with eyes, nose and mouth. Use only in well ventilated areas. Keep tightly sealed. Do not store above 60oC. Keep out of reach of children.
Acidic mixtures can easily “eat away” your skin and can make holes in clothes. However, since vinegar is only 5% acetic acid, it will not irritate the skin and destroy clothes. Sodium hydroxide (commonly called lye or liquid sosa) is used to open clogged kitchen and toilet pipes, sinks, and drains. Its product label shows the following warning:
POISON. Avoid contact with any part of the body. Causes severe eyes and skin damage and burns. Store in a cool dry place and locked cabinet. Harmful or fatal if swallowed.
54
For your safety, you should make it a habit to read product labels before using them. It is also important to know the proper way of storing these products, as shown in the label of Liquid Sosa.
What happens when acids and bases combine? Look back at the pH color chart of Activity 2. You will find a pH value that is not acidic or basic. Mixtures that are not acidic or basic are called neutral. When an acid mixes with a base, water and salt are produced. Such a process is called neutralization. If a basic mixture is added to an acidic mixture, the resulting mixture will no longer have the properties of the acidic mixture. In the same way, if enough acidic mixture is added to a basic mixture, the properties of the basic mixture are changed. This is because the acid and the base in each of the mixtures neutralize each other to produce a mixture with a different set of properties. The process of neutralization has some uses in everyday life. The following are some examples:
Treating indigestion. The acid in our stomach, gastric juice, is hydrochloric acid with low concentration. It helps in the digestion of food. If we eat too much food, the stomach produces more acid which leads to indigestion and pain. To cure indigestion, the excess acid must be neutralized by tablets called antacids. These contain bases to neutralize the excess acid in the stomach.
Using toothpaste to avoid tooth decay. Bacteria in the mouth can change sweet types of food into acid. The acid then attacks the outermost part of the tooth and leads to tooth decay. Toothpaste contains bases that can neutralize the acid in the mouth.
Treating soil. You will recall in the earlier part of this module that some plants grow well in acidic soil while others prefer basic soil. Farmers need to know the pH of their soil. Most often, the soil gets too acidic. When this happens, the soil is treated with bases such as quicklime (calcium oxide), slaked lime (calcium hydroxide) or calcium carbonate. The base is usually spread on the soil by spraying.
Treating factory waste. Liquid waste from factories often contains acid. If this waste reaches a river, the acid will kill fish and other living things. This problem can be prevented by adding slaked lime (calcium hydroxide) to the waste in order to neutralize it.
After completing this module, you learned about the properties of acidic and basic mixtures. You can now prepare indicators from plants anytime you need to use them. You are more aware of the use of the pH scale, which will become more helpful as you study science in higher grade levels. You now recognize the importance of knowing the acidity or basicity of common mixtures we use, as well as the relevant uses of the process of neutralization.
55
References and Links Brady, J.E. & Senese, F. (2004). Chemistry: Matter and its changes, 4th edition. River Street Hoboken, NJ: John Wiley & Sons, Inc Bucat, R.B. (Ed.) (1984). Elements of chemistry: Earth, air, fire & water, Volume 2. Canberra City, A.C.T., Australia: Australian Academy of Science. Bucat, R. B. (Ed.) (1983). Elements of chemistry: Earth, air, fire & water, Volume 1. Canberra City, A.C.T., Australia: Australian Academy of Science. Burns, R. A. (1999). Fundamentals of chemistry, 3rd edition. Upper Saddle River, N.J. Prentice-Hall, Inc. Elvins, C., Jones, D., Lukins, N., Miskin, J., Ross, B., & Sanders, R. (1990). Chemistry one: Materials, chemistry in everyday life. Port Melbourne, Australia: Heinemann Educational Australia. Gallagher, R. & Ingram, P. (1989). Co-ordinated science: Chemistry. Oxford, England: Oxford University Press. Heffner, K. & Dorean, E. (n.d.) Must it rust? The reaction between iron and oxygen. Retrieved Feb 16, 2012 from http://www.haverford.edu/educ/knight-booklet/mustitrust.htm Heyworth, R. M. (2000). Explore your world with science discovery 1. First Lok Yang Road, Singapore. Pearson Education South Asia Pte Ltd. Hill, J.W. & Kolb, D.K. (1998). Chemistry for changing times, 8th edition. Upper Saddle River, NJ: Prentice Hall. Philippines. Department of Education. (2004). Chemistry: Science and technology textbook for 3rd year. (Revised ed.). Quezon City: Author.
56
Suggested time allotment: 5 to 6 hours
Unit 1 MODULE
5
METALS AND NONMETALS
Elements are the simplest form of substances. This means that whatever you do with an element, it remains to be the same element. Its physical state may change but the identity of the element will not. It may form compounds with other elements but the element will never form anything simpler than it already is. There are already more than a hundred elements and are organized in a Periodic Table. Some of them are naturally occurring and some were produced in a laboratory. In this module, you will find out more about the elements. You will see that majority of them are metals, while some are nonmetals. In addition to these are the metalloids, so called because they exhibit properties of both metals and nonmetals.
How are metals different from nonmetals? How are they similar?
Properties of Metals In the earlier grades, you segregated objects according to the material they are made of. You did this when you were starting the habit of 5Rs — recycle, reuse, recover, repair or reduce. Look around you. Which objects are made of metals? What made you say that they are metals?
57
Perhaps, you have been identifying a metal based on its appearance. Most of the time, metals are shiny. They exhibit a luster which is the reason that they are used as decorations. Many metals are ductile. This means that metals can be drawn into wires. An example is copper. The ductility of copper makes it very useful as electrical wires. Gold is also a metal that is ductile; however, it is rarely used as an electrical wire. What could be the reason for this? Some metals are malleable. This means that they can be hammered or rolled into thin sheets without breaking. An example is aluminum. It is passed into mills and rolled thinly to produce the aluminum foil used to wrap food. Most soda cans are made of aluminum, too. Some metals are magnetic. This means that they are attracted by a magnet. The common ones are iron, nickel and cobalt. Get a magnet. Try them in different metals in your home or school. Were they all attracted to the magnet? What metals are these? The general properties of metals are luster, ductility, malleability and magnetic properties. Metals exhibit these properties in varying degrees.
Other properties exhibited by metals In the next activity, you will investigate the electrical conductivity of different materials. This property allows electricity to pass through a material. You will find out whether this property is exhibited by metals or nonmetals. You will use an improvised conductivity tester as the one shown on the right.
These are made from copper. Make sure they are not touching each other.
Activity 1 Which can conduct electricity, metals or nonmetals? Objective In this activity, you should be able to distinguish between metals and nonmetals based on its electrical conductivity.
58
Materials Needed
samples of copper, aluminum, sulfur, iron and iodine white paper improvised conductivity apparatus
Procedure 1.
Place a sample in a sheet of white paper. This will help you observe the samples better. In Table 1, note down the appearance of each of them.
Table 1. Electrical conductivity of different materials Sample
Appearance
Electrical Conductivity
aluminum copper iodine iron sulfur Q1. Which of the samples look like metals? How about nonmetals? 2.
Place the end tip of the improvised conductivity apparatus in contact with each sample. If the tester gives off a sound, the sample is said to be electrically conductive. Otherwise, it is electrically nonconductive. Note: Do not let the end tips of the conductivity tester touch each other.
Q2. Which of the samples are electrical conductors? Which are not? Note them down in Table 1.
In the activity above, you determined qualitatively the electrical conductivity of each sample. However, if you wish to know the electrical conductivity values, a more sophisticated tester may be used such as the one in the figure below. The metallic probe in the figure on the left is the one that comes in contact with the sample. It will measure then display the electrical conductivity value in the liquid crystal display (LCD) screen. Refer to the periodic table found at the end of this unit.
59
The electrical conductivity values are written at the bottom line of each box. It is expressed in x106 Ohm-1cm-1. What do you notice about the elements with electrical conductivity values? Where are they located in the periodic table?
One amazing feature of the periodic table is that all the metals are placed in one side. Those that are on the other side (grayish shade) are the nonmetals. Notice that there is a stair step line formed by some elements which somewhat divides the metals and nonmetals. These elements are the metalloids. They are elements exhibiting properties that are intermediate to metals and nonmetals. Name the metalloids. Name some metals. Name some nonmetals. Which are electrically conductive, metals or nonmetals? Which element has the highest electrical conductivity value? What could be the reason for using copper as an electrical wire more than this element? You might wonder why some metals do not have electrical conductivity values when supposedly all of them possess such property. Notice that these metals are the ones mostly found at the last rows of the periodic table. Elements in those rows are mostly radioactive. This means that the element is very unstable and exists in a very short period of time. In effect, it would be difficult to test for their properties. In the higher grade levels, you will learn that there are ways to infer the electrical conductivities of these elements. Electrical conductivity clearly distinguishes metals from nonmetals but there is one exception. Refer to the periodic table. Which element is electrically conductive even if it is a nonmetal? One form of carbon is graphite. It is commonly available as the black rod in your pencils. Get your sharpened pencil. Place the black rod in between the end tips of your improvised conductivity tester. Make sure that the black rod is in contact with the tips of the tester. What happened? In the higher grade levels, you will learn why carbon (graphite) though a nonmetal is electrically conductive. Look for other objects and test if they are made up of metal or nonmetal. Write down these objects in the appropriate box of the diagram below.
60
Were you able to find a cooking pot as one of your test objects? What element is it mainly made of? Refer to Table 2. This table shows the thermal conductivity values of some elements expressed in Watt/centimeter-Kelvin (W/cmK). Thermal conductivity is the ability of an element to allow heat to pass through it. The higher the value, the better heat conductor an element is. Find the elements that are mainly used for the cooking pots. What can you say about the thermal conductivity of this element compared with the other elements? Is this element, a metal or nonmetal? In general, which are better heat conductors, metals or nonmetals? Based on Table 2, what other elements can be used as cooking pots? Note as well that the malleability of a metal is a consideration in using it as a material for cooking pot. Table 2. Thermal conductivities of some elements Element Copper Aluminum Iron Selenium Sulfur Phosphorus
Symbol Cu Al Fe Se S P
Thermal Conductivity* (W/cmK) 4.01 2.37 0.802 0.0204 0.00269 0.00235
*Kenneth Barbalace. Periodic Table of Elements - Sorted by Thermal Conductivity. EnvironmentalChemistry.com. 1995 - 2012. Accessed on-line: 3/14/2012 http://EnvironmentalChemistry.com/yogi/periodic/thermal.html
Metals and Nonmetals In and Around You In the figure below, you will find the elements that your body is made up of. What element are you made up of the most? Is it a metal or a nonmetal? Of all the elements reported in the graph, how many are metals? How about nonmetals?
61
Data taken from Burns, 1999
Refer to the figure on the next page. The figure shows how much of one element is present in the Earth’s crust relative to the other elements. What element is the most abundant in the Earth’s crust? What comes second? Are these metals or nonmetals?
Data taken from Burns, 1999
62
Refer to the periodic table. What constitutes majority of the elements, metals or nonmetals? Interestingly, even with the fewer number of nonmetals, their abundance is higher than metals. As you have seen above from the two graphs, both living and nonliving systems are mainly composed of nonmetals. As you learned in Module 3, elements form compounds. The percentage abundance of the elements reported in the graphs above accounts some elements that are present in compounds, much like the food ingredients you encountered in Module 3. For instance, sodium is present in sodium chloride. The 18.0% carbon that makes up the human body is mostly compounds of carbon such as the DNA that carries your genetic code.
Oxides of Metals and Nonmetals Similarly, oxygen accounted in the graphs may also be in compounds. Some of these compounds are called oxides. These oxides may be formed when an element is burned. These oxides exhibit different acidities. In Module 4, you learned that there are indicators that you can use to determine such. One of these acid indicators is the litmus paper. What color does the litmus paper show when the sample is acidic? How about when the sample is basic? In the next activity, you will separately burn a sample of a metal and a nonmetal. You will test the acidity of the oxide of a metal and that of the oxide of a nonmetal.
Activity 2 Acidity of the oxides of metals and nonmetals Objective In this activity, you should be able to distinguish between metals and nonmetals based on the acidity of their oxides.
Materials Needed
magnesium (Mg) ribbon sulfur (S) iron wire (holder) alcohol lamp test tube beaker litmus paper (red and blue) water
63
cork watch glass dropper/stirring rod
Procedure 1.
Get a piece of iron wire. Make a small loop at one end. Insert the other end into a cork to serve as a handle.
2.
Get a piece of magnesium ribbon. Describe its appearance. Note this in Table 3.
Q1. Is magnesium a metal or a nonmetal? 3.
Coil a small piece of Mg ribbon (about 2 cm) and place on top of TAKE the loop. Place the looped end of CARE! the wire into the flame of an alcohol lamp. Note what happens. Record your observations in Table 3.
4.
Place 2 mL of water in a small test tube. Add the ash produced when you burned the Mg ribbon. Shake the test tube gently.
5.
Get a watch glass and place a piece each of red and blue litmus papers.
6.
Wet one end of a stirring rod with the solution and place a drop of this solution on a piece of blue litmus paper. Repeat the test on red litmus paper.
Do not inhale the fumes/vapor.
Q2. Which litmus paper changed in color? Describe the change. Note this in Table 3. Q3. Is the oxide of magnesium acidic or basic? 7.
Place 2 mL of water in another test tube. Clean the wire loop and dip in powdered sulfur (S).
Q4. Is sulfur a metal or nonmetal? 8.
Place the looped end of the wire containing the sample over the flame. As soon as the sulfur starts to burn, put the loop into the test tube without touching the water. Remove the loop into the test tube once the sulfur is completely burned. Cover the test tube immediately and shake well.
9.
Get a watch glass and place a piece each of red and blue litmus papers.
10.
Wet one end of a stirring rod with the solution and place a drop of this solution on a piece of blue litmus paper. Repeat the test on red litmus paper.
Q5. Which litmus paper changed in color? Describe the change. Note this in Table 3. 64
Q6. Is the oxide of sulfur acidic or basic? Table 3. Data for Activity 2 Observations Before heating
During heating
After heating
Reaction of its oxide with litmus paper
Magnesium (Mg)
Sulfur (S)
In this module, you learned about the properties of metals and nonmetals. These properties are the ones that determine their uses like aluminum’s malleability to become soda cans, and copper’s ductility to become electrical wires.
Most of the elements are metals. They are shiny, malleable and ductile but just in varying degrees – like electrical and thermal conductivity. Nonmetals are electrically nonconductive except for some forms of carbon.
It is important to note though that most objects are made not of a single material, rather of a combination of materials so they become fitter for a purpose. This is where your knowledge on the properties of materials comes in. Which materials do you combine to make it fit for a purpose? As you can see from the image in this module cover, the electrical wire made of copper was covered with rubber. Rubber is mainly made of compounds of nonmetals such as carbon, hydrogen and chlorine. As you have learned, nonmetals are nonconductors of electricity. Using a nonmetal to cover a metal makes it safer to use as an electrical wire. As you advance to another grade level, there are more properties of matter that you will encounter. It is hoped that you will be able to maximize the properties of different materials to create new beneficial products or find other uses for them.
65
PERIODIC TABLE
66
OF ELEMENTS
67
68
Suggested time allotment: 4 hours
Unit 2 MODULE
1
FROM CELL TO ORGANISM
Overview There are different materials in the environment. There are also diverse kinds of living things. This module will discuss different kinds of living things and what they are made up of. Organ systems work together to help organisms meet their basic needs and to survive. The digestive system helps organisms get energy from the food they eat. The circulatory system moves the nutrients that come from digested food, along with blood, to the different parts of the body. How do you think do the other organ systems work together? Do plants have organ systems, too? Organ systems are made up of organs that have related functions and are grouped together. For example, the mouth, esophagus, stomach, and intestines are organs of the digestive system. The heart, arteries and veins are some parts that make up the circulatory system. Are there organisms that do not have organs? This module introduces you to the different structures that make up an organism. These structures are formed from the grouping together of parts whose functions are related. You will also discover in this module that organs themselves are made up of even smaller parts. Anything that happens to these small parts will affect the functioning of the organs, organ systems, and the whole organism.
What are organisms? What makes them up?
Activity 1 What makes up an organism? Objectives In this activity, you should be able to: 1.
identify the parts that make up an organism, 69
2. 3.
describe the function of each part, and describe how these parts work together in an organism.
Materials Needed
Writing materials Posters and pictures of organisms, organ systems, organs, tissues, and cells
Procedure Read the selection below and answer the questions that follow. You are an organism just like the plants and animals.
Photos: Courtesy of Michael Anthony B. Mantala
Figure 1. Pictures of a human being, plant, and an animal
Have you ever asked yourself what makes you up and the other organisms around you? Figure 2 shows a model of a human torso.
Q1. What parts of the human body do you see? Q2. To which organ systems do these parts belong? Figure 3 shows two other organ systems that you may be familiar with. Photo: Courtesy of Michael Anthony B. Mantala Biology Laboratory, UP NISMED
Figure 2. A model of a human torso
70
Q3. Can you identify these organ systems? Q4. How do these organ systems work together?
Figure 3. Other Organ Systems
The circulatory system is one of the organ systems that make up an organism. It is made up of the heart, blood vessels, and blood. Figure 4 shows a model of a human heart. Your heart is about the size of your fist. It pumps and circulates blood to the different parts of the body through the blood vessels. Certain diseases affect the heart and cause it to function improperly. To learn more about these diseases and what they do to the heart, interview relatives or neighbors who have heart problems or who know of people who have the disease. You can also use the internet and the library to read articles about how certain diseases affect the heart, its parts, and the whole organism. Q5. Refer to Figure 4. What parts of the human heart do you see?
71
Photo: Courtesy of Michael Anthony B. Mantala, Biology Laboratory, UP NISMED
Figure 4. A model of a human heart
Q6. What do you think will happen to the heart if any of these parts were injured or diseased? Q7. If these parts of the heart were injured or diseased, what do you think will happen to the organism? The excretory system is another organ system that makes up an organism. It is made up of different organs that help the body eliminate metabolic wastes and maintain internal balance. These organs include a pair of kidneys. Figure 5 shows a model of a human kidney. What shape does it look like? The kidneys are made up of even smaller parts. Some parts eliminate wastes that are no longer needed by the body; other parts function in the reabsorption of water and nutrients. Like the heart, certain diseases also affect the kidneys and their function. To learn more about these diseases and what they do to the kidneys, interview relatives or neighbors who have kidney problems or who know of people who have the disease. You can also use the internet and library resources to read articles or news clips about how certain diseases affect the kidneys – and the other organs of the body – and the whole organism.
Photo: Courtesy of Michael Anthony B. Mantala, Biology Laboratory, UP NISMED
Figure 5. A model of a human kidney
Q8. Refer to Figure 5. What parts of the human kidney do you see? Q9. What do you think will happen to the kidneys if any of these parts were injured or diseased? Q10.
If these parts of the kidneys were injured or diseased, what do you think will happen to the organism?
Q11.
What procedure can a medical doctor do to correct an injury to these organs?
Organs are made up of tissues. The heart, kidneys, and the parts that make them up are made up of tissues. Figure 6 shows a picture of a muscle tissue. This tissue is made up of cells - the basic units of structure and function in organisms. Photo: http://www.uoguelph.ca/zoology/ devobio/miller/013638fig6-17.gif
Figure 6. Muscle tissues
72
Q12.
What do you think will happen to the organs if these tissues were injured or diseased?
Q13.
If these tissues were injured or diseased, what do you think will happen to the organ systems?
Q14.
If these tissues were injured or diseased, what do you think will happen to the organism?
Plants are also made up of organ systems: the root and shoot systems. The root system absorbs water and nutrients; the shoot system moves them to the different parts of the plant. Q15.
Q16.
In what ways are the functions of the organ systems of plants similar to those of animals?
Photo: Courtesy of Michael Anthony B. Mantala
Figure 7. An orchid showing shoot and root systems
In what ways are they different?
Figure 8 shows a picture of a flower. Flowers are the reproductive organs of plants. Together with the leaves and the stems, they make up the shoot system. Q17. In what ways are flowers similar to the reproductive organs of animals? Photo: Courtesy of Michael Anthony B. Mantala
Q18.
In what ways are they different?
Q19.
How do the flowers, leaves, and stems help plants meet their basic needs?
Q20.
What do think will happen to the plant if any of the parts that make up the shoot system were injured or diseased?
Figure 8. A Gumamela (Hibiscus) flower
Figure 9 shows a picture of the roots of a tree. What parts do you think make up these roots? Q21.
Aside from absorbing water and nutrients, what other functions do the roots serve? Photo: Courtesy of Michael Anthony B. Mantala
Figure 9. Roots of a tree 73
Figure 10 shows a model of a section of a root tip. When you get a small section of a root tip and view it under a microscope, you will see that it is made up of many layers of tissues. You will also see that these tissues are composed of similar cells that are arranged and grouped together to perform specific functions. Q22.
What do you think will happen to the roots if the tissues that make them up were injured or diseased?
Q23.
If the roots were injured or diseased, what do you think will happen to the plant? Photo: Courtesy of Michael Anthony B. Mantala Biology Laboratory, UP NISMED
Figure 10. A model of a section of a root tip showing different plant tissues
Take a closer look at the models of animal and plant cells in Figure 11. Cells are the basic units of structure and function of all organisms. These cells are grouped together to form more complex structures: tissues, organs, and organs systems. Animals and plants are very different organisms and yet, they are both made up of parts that are organized similarly.
Photo: Courtesy of Michael Anthony B. Mantala, Biology Laboratory, UP NISMED
Figure 11. Models of animal and plant cells
Q24.
What do you think will happen to the tissues, organs, and organ systems if these cells were injured or diseased?
Q25.
If the tissues, organs, and organ systems were injured or diseased, what do you think will happen to the organism?
74
Activity 2 Levels of organization in an organism Objectives In this activity, you should be able to: 1.
identify the different levels of organization in an organism,
2.
describe the parts that make up each level of organization and their functions, and
3.
describe how the parts that make up a level of organization affect the higher levels of organization and the entire organism.
Materials Needed
Writing materials Posters and pictures of organisms, organ systems, organs, tissues, and cells
Procedure 1.
From the interviews you have made in Activity 1 and the articles you have read about certain diseases that affect the heart, kidneys, and the other parts of the body, complete the table on page 8. You may use Manila paper if the spaces provided in the table are not enough.
2.
On the topmost row write a disease, which you have read about or learned from your interview, that affects parts of the human body.
3.
In each of the boxes that correspond to the levels of organization, describe how the disease affects the parts that make up each level.
4.
Opposite each level of organization, cut and paste pictures (you may use the pictures that come with the articles) that show how the disease affects the parts that make up the different levels. Another option is to show it through drawing.
75
Table. Diseases and their effects on the levels of organization in an organism Disease: How does the disease affect each of the following levels of organization?
Pictures/Drawings
Organism
Organ System
Organ
Tissue
Cell
After learning the different levels of organization in organisms, can you think of levels of organization that are bigger than the organism?
76
Try this! Complete this graphic organizer with pictures! Humans and animals are organisms... Plants are organisms...
Humans and animals are made up of organ systems...
Plants are made up of organ systems...
Organ systems are made up of organs...
Organ systems are made up of organs...
Organs are made up of tissues...
Organs are made up of tissues...
Tissues are made up of cells... All organisms are made up of cells.
77
Reading Materials/Links/Websites Bright Hub Education. (2009). Science lesson plan: Biological organization. Middle School Science Lessons. Retrieved from http://www.brighthubeducation.com/ Education. (2003). The Pyramid of Life (Levels of Biological Organization). Biology demystified: A self-teaching guide. Retrieved from http://www.education.com/ Scitable by Nature Education. (2008). Biological complexity and integrative levels of organization. Scitable Topicpage. Retrieved from http://www.nature.com/scitable
78
Suggested time allotment: 4 to 5 hours
Unit 2 MODULE
2
PLANT AND ANIMAL CELLS
Overview All organisms, big or small consist of cells. Some organisms are singlecelled, composed of only one cell. Others are multicellular, possessing many cells that work together to form an organism. The moss plant for example, may be made up of hundreds or thousands cells. Your body has billions of cells while very large animals like elephants have trillions. Most cells are so small that they can only be seen using the microscope. It is a special equipment to make small objects like cells look bigger. One kind of microscope used to study cells is called a light microscope. Light microscopes use diffused or artificial light to illuminate the object to be observed. From the simplest to the most powerful and sophisticated microscopes, scientists were able to gather information about cells. What you will see and learn about cells later have been revealed by microscopes. If your school has microscope, your teacher will teach you how to use it through activities you will perform. In this module you will study plant and animal cells, their parts and functions.
Are all cells the same? If not, in what ways are they different?
Cell Parts Use the illustrations that follow to learn about parts of plant and animal cells.
79
Activity 1 Comparing plant and animal cells Objectives After doing this activity, you should be able to: 1. 2. 3. 4.
identify parts of the cell; describe plant and animal cells; differentiate plant cells from animal cells; construct a Venn Diagram to show parts that are common to both and parts that are only found in either plant or animal cells.
Materials Needed
sheet of paper ballpen or pencil Illustrations in Figures 1 and 2
Procedure 1. Study closely Figures 1 and 2. These are diagrammatic presentations of plant and animal cells and their parts.
Figure 1. Parts of a plant cell
80
Figure 2. Parts of an animal cell
Q1. Compare the shape of a plant cell with that of an animal cell as shown in Figures 1 and 2. Q2. Which cell parts are found in both cells? Q3. Which are present only in animal cells? Q4. Which are present only in plant cells? A Venn Diagram shows relationships between and among sets or groups of objects that have something in common. It uses two circles that overlap with one another. The common things are found in the overlapping area, while the differences are in the non-overlapping areas. 2. Using the information you have gathered from Figures 1 and 2, construct a Venn diagram of plant and animal cells on a sheet of paper. Label the overlapping and non-overlapping areas. 3. Present and explain your Venn diagram to class. Q5. Based on your observations and study of plant and animal cells, cite differences and similarities between them.
81
A cell has three basic parts: the nucleus, plasma membrane and cytoplasm. The nucleus is a part of cells which is easily seen. It is very important because it controls all the activities of the other parts that occur within the cell. The nucleus contains materials that play a role in heredity. You will discuss about these materials in the later modules and grade levels. The plasma membrane encloses the cell and separates what is inside it from its environment. It also controls what goes into and out of the cell. The plasma membrane allows entry of materials needed by the cell and eliminates those which are not needed. Q6. What do you think will happen to the cell if the plasma membrane does not function properly? The cytoplasm consists of a jelly-like substance where all the other parts of the cell are located. It does not however, include the area where the nucleus is located. Many different activities of the cell occur in the cytoplasm. You have seen that plant cells have cell walls and chloroplasts that are not found in animal cells. The cell wall is made of stiff material that forms the outermost part of plant cells. This gives shape and protection to them. Recall in your elementary grades that plants make their own food. Chloroplasts are important in plant cells because it is where food is made. It contains chlorophyll, a green pigment, which absorbs energy from the sun to make food for plants.
Q7. What is the purpose of the cell wall in plants? Q8. Look at Figure 1 again. Why are there several chloroplasts in the plant cell? Vacuoles are present in both plant and animal cells. In plant cells, they are large and usually occupy more than half of the cell space. They play a role in storing nutrients and increasing cell size during growth. Some plant vacuoles contain poisonous substances. Vacuoles also store water, thereby maintaining rigidity to cells and provide support for plants to stand upright. Plant cell vacuoles are responsible for the crisp appearance of fresh vegetables. Vacuoles in animal cells are small and are called vesicles. They serve as storage of water and food and also function in the excretion of waste materials. Q9. How would vacuoles in plants serve as defense against animals that eat them? You have observed that centrioles are only found in animal cells. These have a role in cell reproduction which you will take up in Grade 8.
82
You have been introduced to the basic parts of plant and animal cells. Your teacher will discuss the functions of the mitochondrion, golgi body, endoplasmic reticulum (rough and smooth), lysosomes and ribosomes. If you have a microscope you can also study plant cells by doing the next activity. Read and do the activities in the section on “How to Use The Light Microscope” before performing Activity 2.
Activity 2 Investigating plant cells Objectives In this activity, you should be able to: 1. 2. 3. 4. 5. 6.
prepare a wet mount; describe a plant cell observed under the light microscope; stain plant cells; identify observable parts of a plant cell; draw onion cells as seen through the light microscope; and explain the role of microscopes in cell study.
Materials Needed dropper
cover slip glass slide onion bulb scale scalpel or sharp blade
tissue paper iodine solution light microscope forceps or tweezers 50-mL beaker with tap water
Procedure 1.
Prepare the onion scale by following steps indicated in Figure 3. Use the transparent skin from the inner surface of the onion scale.
Be careful in using the scalpel or blade!
CAUTION:
83
Figure 3. Preparing onion scale for microscopic study (Source: University of the Philippines. Institute for Science and Mathematics Education Development (2000). Sourcebook on practical work for teacher trainers: High School biology (vol. 2). Quezon City: Science and Mathematics Education Manpower Project (SMEMDP). p.164)
2.
Following the procedure on how to make a wet mount described in “How to Use The Light Microscope”, prepare one using the transparent onion skin from Step 1. Remember to place it on the glass slide with the inner surface (nonwaxy side) facing up. Check too that the onion skin is not folded or wrinkled.
3.
Examine the onion skin slide under the low power objective (LPO).
CAUTION :
Do not tilt the microscope!
Q10.
How much are these onion cells magnified?
Q11.
In this case, why is it not good to tilt the microscope?
4.
Shift to the high power objective (HPO).
Raise the objectives a little and look to the side while changing objectives!
REMEMBER:
Q12.
Describe the onion cells. 84
5.
Remove the slide from the stage. You can now stain the onion cells with iodine solution.
IODINE STAINS!
6.
Be careful not to spill it on your skin and clothing!
Using a dropper, place one or two drops of iodine solution along one edge of the cover slip. Place a piece of tissue paper on the other edge of the cover slip. The tissue paper will absorb the water, and iodine solution spreads out under the cover slip until the whole specimen is covered with stain (Figure 4).
Figure 4. Staining onion cells (Source: Philippines. Department of Education. (2009). Science and Technology II. Textbook (Rev. ed.). Pasig City: Instructional Materials Development Corporation. p. 23.
7.
Examine the stained onion cells under the LPO and HPO.
Q13.
Did you observe any change in the image of onion cells before and after staining?
Q14.
How did the iodine solution affect the image of the onion cells?
Q15.
What parts of the onion cell can you identify?
8.
Q16.
Draw three to four onion cells as seen under the HPO. Label the parts you have identified. Indicate how much the cells are magnified. Of what importance is the contribution of the microscope in the study of cells?
85
You have learned that the cell makes up all organisms. And that organisms can be made up of just one cell or billions of cells. The module also introduced you to the microscope which has contributed to the valuable information about cell structure and function. You also found out about the fundamental parts of the cell which are the nucleus, plasma membrane and cytoplasm. These parts play very important roles in the survival of cells. Specifically, Activity 1 showed you the similarities and differences in parts of plant and animal cells and the functions of these parts. Other than the three parts first mentioned, the mitochondrion, rough and smooth endoplasmic reticulum, Golgi body, vacuole/vesicle, ribosomes and lysosome are common to them. In fact, these are also present in fungi and protists which you will study in the next module. You have observed in the illustrations that plant cells have a cell wall, and chloroplasts which are not found in animal cells. These have something to do with the nature of plants having tough stems and their being able to produce their own food. On the other hand, animal cells have centrioles which are not found in plant cells. You have seen too the rectangular shape of plant cells as compared to the more or less rounded one in animal cells shown in the illustrations you have studied. You will know and see more of the other shapes of plant and animal cells in the next grade levels. The second activity was a good opportunity for you to have observed real plant cells using the light microscope. The use of stains in studying cells has made cell parts more easy to find, observe and identify.
86
Suggested time allotment: 2 to 3 hours
HOW TO USE THE LIGHT MICROSCOPE If your school has microscopes read this section and perform the following activities. The microscope is a tool which can help you see tiny objects and living organisms. It makes them look bigger. This ability of the microscope is called its magnifying power or magnification. The microscope also has the capacity to distinguish small gaps between two separate points which humans cannot distinguish. It is called its resolving power or resolution. The light microscope uses diffused light from the sun or artificial light to illuminate the object to be observed. From its source, visible light passes through the small or thin specimen to be observed through the glass lenses. As light passes through the lenses, it is bent so specimen appears bigger when it is projected to the eye. The form and structure of the specimen can then be seen because some of their parts reflect light. This section will introduce you to the parts of the light microscope and their functions. More importantly, it will teach you how to use it properly for successful cell study and other investigations.
What are the parts of the microscope and how does each part function? How do you use the microscope?
Objectives After performing this activity, you should be able to: 1. 2. 3. 4. 5.
handle the microscope properly; identify the parts of the microscope; describe what parts of the microscope can do; prepare materials for microscope study; focus the microscope properly; 87
6. 7.
compare the image of the object seen by the unaided eye and under the microscope; and compute for the magnification of objects observed under the microscope.
Materials Needed
lens paper light microscope tissue paper or old t-shirt newspaper page glass slide and cover slips
pencil dropper scissors tap water forceps or tweezer
Procedure A. The Microscope, Its Parts and their Functions 1. Get the microscope from its box or the cabinet. Do this by grasping the curved arm with one hand and supporting the base with the other hand. 2. Carry it to your table or working place. Remember to always use both hands when carrying the microscope. 3. Put the microscope down gently on the laboratory table with its arm facing you. Place it about 7 centimeters away from the edge of the table. 4. Wipe with tissue paper or old t-shirt the metal parts of the microscope. Q1. What are the functions of the base and the arm of the microscope? 5. Figure 1 shows a light microscope that most schools have. Study and use this to locate different parts of the microscope.
Figure 1. The light microscopes and its parts
6. Look for the revolving nosepiece. Note that objectives are attached it. should know that there are lenses inside the objectives. Q2. What have you observed about the objectives? 88
You
Most schools have light microscopes with three objectives. Others have four. Usually, the shortest one marked 3x, 4x or 5x is called the scanner. The low power objective (LPO) is marked 10x or 12x while the high power objective (HPO) is marked 40x, 43x or 60x. The objectives magnify the object to be observed to a certain size as indicated by the 3x, 10x or 40x, etc. marks. If the longest objective of your microscope is marked 97x or 100x or OIO or the word “oil” on it, then it has an oil immersion objective (OIO). This objective is used to view bacteria, very small protists and fungi. The OIO requires the use of a special oil such as quality cedarwood oil or cargille’s immersion oil. 7. Find the coarse adjustment. Slowly turn it upwards, then downwards. Q3. What is accomplished by turning the coarse adjustment upwards? downwards? 8. Looking from the side of the microscope, raise the body tube. Then, turn the revolving nosepiece in any direction until the LPO is back in position. You will know an objective is in position when it clicks. Note that the revolving nosepiece makes possible the changing from one objective to another. Q4. What is the other function of the revolving nosepiece? Q5. Which part connects the eyepiece to the revolving nosepiece with the objectives? 9. Locate the eyepiece. Notice also that it is marked with a number and an x. Know that the eyepiece further magnifies the image of the object that has been magnified by the objective. If the eyepiece is cloudy or dusty, wipe it gently with a piece of lens paper.
REMEMBER:
Only use lens paper in cleaning the lenses of the eyepiece and the objectives.
10.
Look through the eyepiece. Do you see anything?
11.
Now, locate the mirror. Then, position the microscope towards diffused light from the windows or ceiling light. Look through the eyepiece and with the concave mirror (with depression) facing up, move it until you see a bright circle of light.
89
Never use direct sunlight as a light source to view objects under the microscope. Direct sunlight can permanently damage the retina of the eye.
CAUTION:
The bright circle of light is called the field of view of the microscope. Adjust the position of the mirror so that it is not glaring to the eyes. Practice viewing through the microscope using both eyes open. This will reduce eyestrain. Q6. What are the two functions of the eyepiece? Q7. Describe the function of the mirror. 12.
Locate the diaphragm. While looking into the eyepiece, rotate the diaphragm to the next opening. Continue to do so until the original opening you used is back under the hole in the stage.
Q8. What do you notice as you change the diaphragm openings? Q9. What can you infer as to the function of the diaphragm? 13. Q10. 14.
Find the inclination joint. What parts of the microscope are being connected by the inclination joint? Grasp the arm and slowly pull it towards you. Sit down and try looking through the eyepiece.
Q11. What does this movement do?
REMEMBER:
Tilting of the microscope allows one to do observations while seating down. This is however, only done when materials observed do not contain liquids like water.
90
B. Making a Wet Mount A specimen is a part or sample of any material e.g. plant, animal, paper or mineral, for study or examination under the microscope. Specimens should be small and thin for light to pass through them. 15.
Q12.
Cut out a small letter “e” from a newspaper page. Using forceps or tweezers place it in the center of a glass slide in an upright position. What makes the letter “e” suitable for observation under the microscope?
16. Add a drop of tap water over the specimen. It will act as a mounting medium and make clear the image of the specimen. Position the cover slip at 45° with one side touching one edge of the water on the slide (Figure 2).
17.
Figure 2. Making a wet mount
Slowly lower the other edge of the cover slip until it rests on the water and the printed letter. Bubbles are perfect circles you see on your preparation. Remove or minimize trapped bubbles by gently tapping the cover slip with the eraserend of a pencil. Make the bubble move towards the edge of the cover slip.
C. Observing Specimens 18.
Put the slide on the stage. Make sure that the letter is in the center of the hole in the stage and under the LPO. Hold it firmly with the stage clips.
19.
Watching from the side, carefully lower the body tube until the end of the LPO almost touches the cover slip.
20.
Look through the eyepiece. Slowly turn the coarse adjustment upwards to raise the objective until the letter “e” appears. Continue until you see the letter clearly. This would indicate that you have focused it already.
Q13.
Describe the position of the letter as seen under the microscope.
Q14.
Compare the image of the letter that you see using your unaided eye with what you see through the microscope.
21.
Q15. 22.
Look through the microscope again. Slowly move the slide to the right, then to the left. To which direction does the image move? Move the slide to the center. To shift to the HPO, raise the body tube first. Looking from the side, turn the revolving nosepiece to put the HPO in place. 91
Then, using the fine adjustment slowly lower the objective till it almost touches the cover slip. Looking through the eyepiece, turn the fine adjustment until you see the clearest image. Q16.
Why do you have to watch from the side when changing objectives?
Q17.
Why should the fine adjustment knob be used only with the HPO?
Current microscope models are said to be parfocal. This means the image in clear focus under the low power objective, remains focused after shifting to HPO. If the microscope you are using is not parfocal, slightly turn the fine adjustment knob in either direction to get a clear picture. 23. Look through the eyepiece again. Then, shift to the LPO, and the scanner. Observe closely the image of the letter. Q18.
In which objective/s can you see the whole letter “e”?
Q19.
What are the advantages of using the HPO? the disadvantages?
Q20.
In which objective is the light darker? brighter?
D. Magnifying Power of the Light Microscope Can you recall the functions of the objectives and the eyepiece? The magnification of a specimen can be calculated by multiplying the number found in the eyepiece with the number found on the objective being used. So, if a specimen is viewed using a 10x objective and a 10x eyepiece it will be magnified 100 times. 24.
Examine the numbers indicated on the eyepiece and scanner.
Q21.
How much is the letter “e” you are now viewing under the scanner magnified? under the LPO? Under the HPO?
Q22.
If a cell being observed has been magnified 200x under the HPO, what is the magnifying power of the eyepiece used?
Q23.
In what ways would the microscope contribute to the study of different objects and organisms?
25.
After using the microscope, lift the stage clips to remove the slide from the stage. Wash and wipe or air dry the slide and cover slip. Keep them in their proper places. Dispose trash or other materials properly.
92
You have just familiarized yourself with the light microscope, its parts and their functions. Similarly, you have practiced using it. After every use of the microscope, prepare it for storage following these steps: 1. Turn the revolving nosepiece until the LPO is in place. 2. Lower down the body tube so that the end of the objective is approximately 1 cm above the stage. 3. Position the clips so that they do not extend beyond the sides of the stage. 4. Rotate the diaphragm until the smallest opening is in position. 5. Let the mirror stand on its edge with the concave side facing the user to protect it from dust. 6. Some microscope boxes have a socket for the eyepiece. In this case, remove the eyepiece from the body tube and place it in the socket. 7. Put back the microscope’s plastic cover. If the original plastic cover has been lost or destroyed, use any clean plastic bag big enough to cover the microscope. 8. Carry the microscope as described in Step 1 of Procedure A. Put it back in its case or storage cabinet or return it to your teacher. Knowledge about objects and organisms revealed by the microscope is of great value not only to students like you but also to everyone who wish to study and understand life. It is but important for you to know how to take care of this tool for an efficient and longer use. Here are some practices to achieve this: 1. Check the microscope before and after use. Report any missing or damaged part to your teacher. 2. Use a clean tissue paper or soft cloth like old t-shirt to clean the mechanical parts of the microscope. 3. Prevent liquids, especially acids and alcohol from spilling on any part of the microscope. Always use a cover slip in observing wet mounts. 4. Check for moisture (such as from condensation of human breath) in the eyepiece. This may happen due to prolonged observation of specimens. Wipe with lens paper. 5. Avoid tilting the microscope while observing wet mounts. Water might flow into the mechanical parts of the microscope causing them to rust. Select a chair with suitable height so that both forearms can be rested on the table during observation. 93
6. Never store the microscopes in a chemical laboratory or any place where there are corrosive fumes. Make sure there are silica get packs inside microscope boxes or storage cabinet to absorb moisture. The microscope has become an important investigative tool in studying objects and organisms around you. Knowing its parts as well as proper manipulation and care will make your study of science effective, interesting and more meaningful.
Reading Materials/Links/Websites Hwa, K. S., Sao-Ee, G., & Luan, K. S. (2010). My pals are here! 6A science. (International Ed.). Singapore: Marshall Cavendish. Miller, K. R., & Levine, L. (2006). Prentice Hall biology. Upper Saddle River, NJ: Pearson. Philippines. Department of Education. (2009). Science and Technology II textbook. (Rev. ed.). Pasig City: Instructional Materials Development Corporation. Reyes, V.F., & Alfonso, L. G. (1979). The microscope: Part 1. Manila: AlemarPhoenix Publishing House. http://www.cellsalive.com/cells/cell_model.htm www.microscope-microscope.org/activities/school/microscope-use.htm www.biologycorner.com/bio1/microscope.html
94
Suggested time allotment: 4 hours
Unit 2 MODULE
3
LIVING THINGS OTHER THAN PLANTS AND ANIMALS
Overview In this module, you will start examining life forms other than the plants and animals you studied in Grades 3 through 6. You will begin with the macroscopic forms or parts that you can see and move to the barely noticeable ones, using a magnifying lens. If your school has a microscope, you can observe the truly microscopic forms as well. These cannot be seen by the naked eye, not even through magnifying lenses. These life forms are in the soil, water and air all around us. They are on our body and inside it, on the food we eat and the things we use. Many are useful to humans while some are harmful and may cause disease. In studying them, we develop inquiry skills and use a powerful observation device, the microscope, if this is available. You and your classmates will perform two hands-on activities in this module, which entail observing, recording, communicating by drawing and writing, going out in the school grounds to collect specimens, inferring and answering questions. In so doing, you expand your knowledge about the living world and appreciate the diversity in life forms. What are the other living things besides plants and animals? Which are useful to us? Which are harmful?
Activity 1 Are these also plants? Objectives In this activity, you will: 1. observe life forms other than those you studied from Grades 3 through 6, 95
2. use a magnifying lens to observe them, 3. share what you know about these life forms with classmates and groupmates, and 4. compare them with known living things studied in Grades 3 to 6.
Materials Needed
Live specimens from teacher Magnifying lens
Procedure 1. Look* at the live specimen shown by your teacher which is like the photo on the right. Q1. Is it a plant? Q2. What is its name? Q3. What is the reason for your answer in Q1?
*Warning: Do not touch the specimen with your bare hands, taste or smell it, especially those of you who have known allergies and if the specimen is not eaten. It may be poisonous. 2. Look at the second live specimen your teacher will show you. It is similar to the photo below:
96
Q4. Q5. Q6.
Is it a plant? What is its name? What is your reason for your answer in Q4?
3. Compare the two specimens shown by your teacher. Q7. Q8. Q9. Q10. Q11.
How are they different? How are they alike? Do you know of other living things like the two above? If so, describe these living things. How did you know about them? Write their names if you know them.
4. Observe the third specimen to be shown by your teacher. She will show you something like this photo grabbed from an internet source.
http://www.treeboss.net/tree-trunk-splotches.htm
Q12. Q13. Q14. 5.
What do you think it is? Is it a plant? Give a reason for your answer in Q13.
Observe these three other things your teacher prepared for you to observe: a.
b.
Or,
97
c.
And, d. Photo credits: potato by A. Encarnacion, old banana peeling and bread by R. Reyes, and http://www.hawaii.edu/reefalgae /invasive_algae/chloro/enteromo rpha_flexuosa.htm downloaded 12 March 2012 for the “green stuff.”
Warning: Do not touch (a), (b), or (c) with your bare hands. Do not smell or taste them either. Some sensitive individuals may be allergic to them. 6. Describe what you see in each (a) and (b) or (c). Q15. Q16.
(a) (b or c)
7. Describe (d). Q17.
(d)
8. What do you think the growths on (a), and (b) or (c) are? Q18. Q19.
(a) (b) or (c)
9. How about (d), what do you think it is? Q20. 10.
(d) Discuss your answers with your classmates and teacher in class.
What you saw are also living things. There are living things or organisms that cannot be readily identified by the usual parts of plants we recognize like roots, stems, leaves, flowers, or fruits though they may have the green color and some plant-like parts. There are also living things that we can see only when we use magnifying lenses. Tomorrow, we will go out and look for more of these kinds of living things which are not like the plants we learned about in the lower grades. Bring plastic gloves and plastic bags at least one each.
98
Activity 2 What other living things are found in the school grounds? Objectives In this activity, you will: 1. 2. 3. 4. 5. 6. 7. 8.
hunt for life forms that are doubtfully plants, collect specimens of these life forms, observe these life forms using a magnifying lens, describe/draw them, describe their habitats, infer their needs, compare with others observed in the previous activity, and group together those that have similarities.
Materials Needed
clear plastic bag plastic gloves forceps, tweezers or tongs magnifying lens
Procedure 1. Bring the first three materials listed when you go out into the school grounds. Look for other things that are plant-like in the school grounds. Your teacher will suggest where to go and what to collect. 2. Go back to the classroom and observe what you collected with a magnifying lens. Q1.
Describe what you see. Draw it.
Q2.
Describe the place where you found it.
Q3. Q4.
What do you think it needs to live and grow? Does it look like any of the organisms you saw yesterday? If so, which one?
99
3. Find out from your teacher the names of all the living things you observed in Activities 1 and 2. Q5.
How are they different from the living things you already know about and studied in the lower grades?
For your homework, find out from reference books and the internet under which big groups the living things you studied belong. Find out the other members of these groups, the characteristics they exhibit, their uses to humans, as well as negative effects. Put the information you collected in a table like the one below: Name of organism
Big group/ Other Examples
Characteristics
Uses/ Benefits
Harmful Effects
What are the similarities among these groups? How are they different from each other? How are these big groups different from the groups of animals and plants studied in Grades 3-6? Discuss in class, with your classmates and teacher, the beneficial and harmful effects of members of these groups. What you studied in this module are the big groups of Fungi, Algae and Bacteria which are different from the two big groups of Animals and Plants studied in Grades 3-6. You did not study many other members of these groups however. There are many more interesting members of these groups which you will learn about in the higher grades. Together, these three groups plus the groups of plants and animals studied in the previous grades make up the living world. We are a part of this living world. We have to learn to live with different kinds of living things. Ensuring the survival of other kinds also ensures our own survival. If your school has a microscope, you can do Activity 3. It is an OPTIONAL activity.
100
Activity 3 What do these living things look like under the microscope? Objectives In this activity, you will: 1.
prepare slides of the growths on old banana peeling, and/or bread mold, lumot, and the bacterial colony you saw in Activities 1 and 2,
2.
observe these living things using a microscope,
3.
draw and describe these living things, and
4.
be able to label the parts and describe the function of these parts based on reference photographs or drawings and library/internet research.
Materials Needed
slides and cover slips dissecting needles (may be improvised) dropper cotton, gauze or clean absorbent cloth clean water
Procedure 1.
Get a small part of the white, cottony growth on the decomposing banana.
2.
Spread it with a needle until only a thin layer is on the middle of the glass slide.
3.
With the dropper, wet the spot with a drop of water.
4.
Cover with the cover slip by putting down one side first and gently laying down the cover slip until it is flat over the specimen.
5.
Place it on the microscope stage just under the low power objective (LPO).
Q1. 6. Q2.
Draw what you see. Focus until clear, then shift to the high power objective (HPO). Draw what you see.
101
Q3.
Describe what you see under the LPO and HPO.
Q4.
Label the parts based on a reference photo or drawing your teacher shows you.
7.
Do the same for the growth on the bread, lumot, and Z on the potato.
8.
Discuss your findings with your teacher and classmates.
102
Suggested time allotment: 5 to 6 hours
Unit 2 MODULE
4
REPRODUCTION: THE CONTINUITY OF LIFE
Overview The beginning of a new life is truly a remarkable event. The sight of a chick making its way out of the cracked shell or a germinating seed slowly pushing through the soil can leave one fascinated. The ability of an organism to produce new individuals is one of the characteristics that distinguishes living things from nonliving things. This ability is called reproduction. In the previous modules, you have already begun to explore the diversity of organisms. These organisms bring about the continuation of their own kind through reproduction. And although these organisms have different methods of reproduction, every method leads to the beginning of a new life. This module will discuss the different modes of reproduction in representative plants, animals, and microorganisms. Investigations are included in this module to help you understand the different ways that organisms reproduce and differentiate the offspring resulting from each mode of reproduction.
What are the different modes of reproduction? How can we use this knowledge in growing plants?
Modes of Reproduction In order to continue their own kind, organisms must reproduce. Organisms may reproduce either asexually or sexually. I. Asexual Reproduction There are several ways by which organisms reproduce asexually. In the following activity, let us examine how potatoes reproduce.
103
Activity 1 Can you grow new plants from “eyes”? A potato tuber is a specialized stem which functions as a food storage organ. Let us investigate how tubers can be used in growing new plants.
Objectives After you have performed this activity, you should be able to: 1. describe how potatoes reproduce. 2. explain what vegetative reproduction is. 3. describe the advantages of growing plants using vegetative reproduction.
Materials Needed
1 potato 5 big cans filled with garden soil (you may use big cans of powdered milk) trowel knife
Procedure potato eye (bud)
1. Examine the potato. Can you see depressions? These are the “eyes” or buds.
Figure 1. Potato eyes. 2. Cut the potato into pieces with each piece having an “eye”. Observe how the cut pieces look. 3. Set aside the cut pieces for 2-3 days. Draw and describe how the cut pieces look after 3 days. 4. After 3 days, plant each piece in a can, about 10-cm deep. Set the tuber so that the “eye” points upward. 104
Q1. Can you give a reason why it is better to plant the cut pieces with the “eye” pointing upward? 5. Set aside the cans in a shady area. Water the soil everyday to keep it moist. Q2. How many “eyes” from each potato were you able to get? Q3. How many new shoots grew from each potato “eye” you planted? Q4. What is the advantage of using this type of propagation? 6. Report the progress of your work to your teacher. Discuss your work in class. After this activity, you may transplant the potato plants in your school garden. You may harvest the potatoes within 10 weeks. Check how many potatoes you can harvest from one plant.
The activity that you have performed shows how potatoes are propagated vegetatively. From a single potato, several new potato plants can be produced. Potato “eyes” are axillary buds where shoots can emerge. Vegetative reproduction is a kind of asexual reproduction where a new individual, known as the offspring, is produced from a single parent. Aside from potatoes, many economically important plants can be propagated vegetatively. The kalanchoe, a medicinal plant, can reproduce through its leaves (Figure 2). Plantlets can grow around the leaf margin.
Figure 2. Plantlets grow around the leaf margins of the Kalanchoe. Do you know other examples of plants that can be propagated through vegetative reproduction? In the lower grades, you have learned that during reproduction, certain traits are passed on from parent to offspring. These traits are in the form of codes 105
contained in genes. Genes are found in chromosomes which are in turn located in the nucleus of cells. In asexual reproduction, the parent and the resulting offspring have the same genes and this is the reason why they have the same traits. In other words, we can say that they are genetically identical. Why do we use vegetative propagation to grow plants? Vegetative propagation results in plants that reach maturity faster than plants grown from seeds. Another good thing about vegetative propagation is that the same good agricultural traits such as taste, yield, and resistance to pests will be passed on from generation to generation. But one disadvantage is that the population might be wiped out if environmental conditions become unfavorable. Let us now look at other types of asexual reproduction.
Activity 2 Can one become two? While walking to school, have you noticed greenish growth on barks of trees or on slippery concrete walkways? What could this organism be? Let us observe closely what organism this might be. Objectives After you have performed this activity, you should be able to: 1. describe how Protococcus reproduce. 2. explain what fission is. 3. infer the characteristics of the offspring of Protococcus. Materials Needed
Scalpel or blade Microscope slide Cover slip
Microscope Tap water in clean bottle Dropper
Procedure Preparation for Activity 1. Look for barks of trees, stones, rocks, moist flower pots that have greenish growth. 2. Get the greenish growth by scraping the sides. 106
3. Soak the scrapings in water overnight to separate the soil particles and debris from the microorganisms. Day 1 1. Put a small amount of scraping on a slide. 2. Add a drop of water. 3. With 2 dissecting needles, carefully tease or separate the scraping and mix it with the water. 4. Gently place a cover slip on the slide. Examine the scraping under the low power objective. Look for a cell similar to the figure on the right. 5. Show your teacher the Protococcus cell that you have located. 6. Protococcus reproduces by dividing. Dividing cells are separated by a wall-like structure. Look for Protococcus cells that are dividing.
Figure 3. Protococcus is a round singlecelled green alga.
7. Shift to high power objective. Q5. Draw the dividing Protococcus cells that you have identified.
This type of asexual reproduction is called fission. The cell divides to form two identical daughter cells. Each daughter cell continues to grow until it becomes as large as the parent cell. Q6. Research on other examples of unicellular organisms that reproduce through fission.
Budding Budding is another type of asexual reproduction. Yeast, hydra, and sponges reproduce this way. Figure 4 shows how yeast, a microorganism used in baking, reproduces by budding. In budding, a new individual may form as an outgrowth of the parent. The outgrowth separates from the parent and becomes a new individual.
Figure 4. Budding in yeast. 107
Spore Formation Have you seen a piece of bread with mold growing on it? The black, round structure at the tip of a stalk is called a spore case which contains the spores. When the spore case opens, the tiny spores are released and may be carried by wind or water. Once the spore lands on a favorable environment, it develops into a new organism. Under the microscope, a bread mold with a spore case looks like the one in Figure 5.
spore case
stalk
Figure 5. Bread mold spore case Formation of spore is another type of asexual reproduction common among molds or fungi.
Regeneration Animals can also reproduce by regeneration. Did you know that when a hydra is cut into several pieces, a process known as fragmentation, each piece can grow into another hydra? In certain types of starfish, an arm that breaks off from the body can develop into a new individual.
II.
Sexual Reproduction
Sexual reproduction is a mode of reproduction that involves two parents. Parents produce reproductive cells called gametes through a type of cell division called meiosis. Meiosis will be discussed in detail in Grade 8. Gametes from the two parents unite in a process called fertilization. The fertilized cell is referred to as a zygote which develops into a new organism. Organisms reproduce sexually in a number of ways. Let us take a look at the different ways how representative microorganisms, plants, and animals reproduce sexually.
Conjugation Some microorganisms undergo sexual reproduction by a process called conjugation. An example of a microorganism that reproduces by conjugation is Spirogyra, a green alga. Spirogyra can be found in freshwater habitats such as ponds and rivers. During conjugation, a bridge forms between two cells of two Spirogyra filaments lying side by side. The contents of one cell pass into the other cell through the bridge, emptying the other cell. The contents of both cells combine in the other cell and form the zygote. This zygote is able to secrete a substance that forms a wall around itself for protection against unfavorable environmental conditions (e.g. when 108
the pond dries up). When conditions become suitable for growth and development, the zygote grows into a new individual.
Sexual Reproduction in Flowering Plants The flower is the reproductive organ in flowering plants. Flowers have structures that produce the gametes necessary for reproduction. Let us take a look at the parts of a gumamela flower.
Activity 3 Structure of a gumamela flower Objectives After you have performed this activity, you should be able to: 1. 2.
distinguish the male and the female reproductive structures of a gumamela flower describe the function of each structure in reproduction.
Materials Needed
2 gumamela flowers (1 fresh and 1 withered) 1 gumamela bud
Hand lens Scalpel or Razor blade
Procedure 1. Examine the entire flower and the part of its stem. Q6.
Describe how the flower is attached to the stem.
2. Examine the bud, an unopened flower. Identify the sepals. Q7.
What is the function of the sepals in the unopened flower?
3. Remove the sepals and petals. The most important reproductive parts remain. The innermost part is called the pistil. The pistil has a broad base called the ovary and a narrow stalk called the style. At the top of the style is the stigma. Touch the stigma in a relatively fresh opened flower, in a bud and in a withered one. Q8.
On which flower does the stigma feel sticky?
Q9.
Why do you think the stigma is sticky?
4. Cut through the ovary and examine the parts with a hand lens. Q10.
How many compartments do you find?
109
Inside the compartments are ovules which contain the egg cell (female gamete). 5. Observe the structures attached to the style. These are the stamens. Touch the tip of a stamen or tap it lightly over a piece of white paper. The powdery materials at the tips are made up of pollen grains. Sperm cells (male gamete) are produced inside these grains. 6. Take a whole flower. Measure the distance between a pollen grain on a stamen and the ovary where the ovule is. Q11. How do you think pollen grains reach the pistil? Pollination brings together the gametes of a flower and it occurs when a pollen grain of the right kind lands on the stigma of the pistil. Each pollen forms a tube that grows down through the pistil and reaches the ovule in the ovary. One of the nuclei in the pollen tube unites with the egg nucleus in the ovule to form a zygote. The other sperm nucleus combines with another bigger nucleus in the ovule which develops into the endosperm.
Sexual Reproduction in Humans and Animals Humans (and all animals that reproduce sexually) have cells called gametes. Gametes are formed during meiosis and come in the form of sperm (produced by males) or eggs (produced by females). When conditions are right, sperm and egg unite in a process known as fertilization. The resulting fertilized egg, or zygote, contains genes from both parents.
Comparison of Asexual and Sexual Reproduction In asexual reproduction, a single organism is the sole parent and the offspring is genetically identical to the parent. In sexual reproduction, two parents produce offspring that have unique combinations of genes. Offspring of sexual reproduction differ genetically from their siblings and both parents.
Summary 1. Organisms must reproduce to continue their own kind. 2. There are two major modes of reproduction: asexual and sexual reproduction. 3. Asexual reproduction gives rise to offspring that are identical to the parent. 4. Individuals that reproduce through sexual reproduction need two parents, a male and a female, that produce egg cell and sperm cell. 5. Sexual reproduction gives rise to offspring that are a combination of the traits from its parents.
110
Suggested time allotment: 8 hours
Unit 2 MODULE
5
INTERACTIONS
Overview The environment is a collection of living and nonliving things. Mosses growing on rocks, garden snails gliding on garden fences, and fish swimming in water are just a few examples of how living and nonliving things interact. The living components of the environment are also called organisms. The nonliving components make up the physical environment of these organisms. Organisms that belong to the same species and live in the same place form a population. The moss that grows on rocks makes up a population. Populations that live in the same place and interact with each other form a community; goats grazing on grass, chickens feeding on grains, and lizards preying on insects make up a community. Interactions between organisms and their environment are also a familiar sight: carabaos helping farmers till the soil, earthworms burrowing in the ground, and birds using twigs to build their nests. Organisms interact with each other and their environment to meet their basic needs and survive. Some interactions are beneficial; others are harmful. There are also interactions in which populations of organisms are neither benefitted nor harmed. All these interactions take place in ecosystems. In this module, you will discover more about ecosystems, the components that make them up, and the interactions that take place among the components of the environment. How do organisms interact with each other and with their environment? How is energy transferred from one organism to the other?
In Module 1, you have been introduced to the concept of levels of organization in organisms. This module will introduce you to levels of organization that are beyond the level of the organism. 111
Activity 1 What does it mean to be alive? Objectives In this activity, you should be able to: 1. identify the components of the environment, 2. compare living and nonliving things, and 3. describe how organisms interact with each other and with their environment.
Materials Needed
Drawing and writing materials Rocks whose surface is grown with small plants Magnifying lens
Procedure 1. Visit your school garden or a pond near your school. On a separate sheet of paper, describe or draw the place. Q1. What are the things that you see in your school garden or the pond? Q2. Which of these things are living? Which of these things are nonliving? Q3. Observe the things that you identified as living. What do they have in common? Q4. Observe the things that you identified as nonliving. What do they have in common? Q5. What interactions do you observe happening among the living and nonliving things? Q6. What makes living things different from nonliving things? 2. Observe the rocks in your school garden or the pond near your school. Do they look like that shown in Figure 1? If so, use a magnifying lens to see the details of the Photo: Courtesy of Michael Anthony B. Mantala small plants. These small plants make up a population. Figure 1. Small plants growing on rocks Q7. What do these small plants need that is provided for by the rock? 112
Q8. Where do you find these rocks that are inhabited by small plants? Q9. What other things in the environment are inhabited by these small plants? Where do you find these things? Q10. Why do you find them in these places? Figure 2 shows a fence populated by small plants. They usually grow on fences during the rainy season. Q11.
Do you also see small plants growing on the fences of your school?
Q12.
What other living and nonliving things did you see in the school garden or the pond? Do you see them in other parts of the school? Explain your answer.
Photo: Courtesy of Michael Anthony B. Mantala
Figure 2. Small plants growing on fences
Figure 3 shows a picture of populations of different kinds of plants. Together, they form a community. Q13.
Do you know of a similar place near your school where you see communities of organisms?
Q14.
Are the things you find in your school garden or the pond the same things that you find in the backyard of your house? Explain your answer.
Q15.
Photo: Courtesy of Michael Anthony B. Mantala
Figure 3. Different kinds of plants
How do living things interact with each other and with their environment?
Your environment is home to many kinds of living and nonliving things. You also see interaction between them like in the rocks and fences that are inhabited by small plants and algae. These rocks that are usually found in wet places provide anchorage and nutrients to the small plants and algae.
Activity 2 Housemates? Ecomates! Objectives In this activity, you should be able to: 1. describe interdependence among the components of the environment, 113
2. explain how organisms interact with their environment to survive, and 3. infer what happens to organisms if their environment is not able to provide them with their basic needs.
Materials Needed
Eight (8) – 500mL wide-mouthed glass jars with covers Two (2) liters of water allowed to stand overnight Hydrilla (or other aquarium plants) Snails and guppies (or other aquarium fishes) Light source Optional: Bromthymol blue solution (BTB) – an indicator that is used to test for the presence (or absence) of carbon dioxide
Procedure 1. Fill each container with water until it is two thirds full. Optional: Add 15mL of BTB to each container. Note that this volume of BTB will depend on the amount of water in the container and how diluted the indicator is. Setup A1 B1 C1 D1
1 – With strong light Water only (control)
Setup A2
Water with snails and guppies only Water with Hydrilla only
B2
Water with snails, guppies, and Hydrilla
D2
C2
2 – Without light Water only (control) Water with snails and guppies only Water with Hydrilla only Water with snails, guppies, and Hydrilla
3. Use the chart above to set up and label the containers. 4. Cover all the jars. 5. Copy Table 1 on a separate sheet of paper to record your observations of changes, if any, in the things that were placed in each of the containers. 6. Record data each day for three days. Also include in your data a description of the health or condition of the organisms and where they stay most of the time in the container. Optional: If you use BTB, get a 10 mL sample of water from each container then add 5 drops of the indicator. Observe for changes in color, if any. Do this each day for three days.
114
Table 1. Interactions among organisms and their environment Setups Day 1
Observations Day 2
Day 3
A1
A2
B1
B2 C1
C2
D1 D2
Q16.
Where did the snails and fish stay most of the time in each of the containers each day for three days? Explain your answer.
Q17.
What happened to the organisms in each of the containers after three days?
Q18.
In which container/s were the organisms still alive? Which organisms are these?
Q19.
What do you think will happen to the organisms in each of the jars when left closed for a longer period of time? Why do you think so?
Questions 19-21 are additional questions if you used BTB. Q20.
In which container/s did you observe change in color on each day for three days?
Q21.
Bromthymol blue changes color to yellow in the presence of carbon dioxide. Which jar/s contained carbon dioxide?
Q22.
What explains the presence of carbon dioxide in this/these container/s? 115
Q23.
How do plants and animals depend on each other?
The plants give off oxygen in the presence of light. The fishes and snails need oxygen to survive. Plants need carbon dioxide given off by the fishes and snails to survive. What you observed in this activity are interactions that take place in an aquarium. There are other kinds of interactions and interdependence among organisms and their environment in bigger ecosystems.
Ecological Relationships In the environment, there are plants, animals, and microscopic organisms such as bacteria and fungi. A group of organisms of the same kind living in the same place at the same time is called a population. Q24. In figure 4 below, what populations of organisms do you see?
Photo: Courtesy of Rodolfo S. Treyes
Figure 4. An example of an ecosystem with different organisms Populations that interact in a given environment form a community. In a community interactions within and among populations may have important influences to death rate and birth rates of the organisms and, in turn, on population growth and size -- these interactions may have positive, neutral, or even negative influences on interacting populations. Look at figure 5 below. What kind of interaction do the ants and aphids exhibit?
116
A
B
Figure 5. A. Interacting populations of ants and aphids. B. An ant may take honeydew from the back of an aphid. Aphids are small insects that suck liquid containing sugar from the conducting tissues of plants. These aphids get a certain amount of sugar and other nutrients from this liquid. However, much of the liquid called honeydew is released through the aphids’ anus. The ants consume this honeydew as food. The ants, in turn, protect the aphids from their insect predators. Thus, both species benefit from each other. This interaction between the populations of ants and aphids is referred to as mutualism. Some interactions among organisms are easier to determine than others, and some effects can easily be observed. Study the photographs that follow. Figure 6 shows fern plants growing on a trunk of a Narra tree. What kind of relationship do you think do these two organisms have?
Figure 6. Fern plants growing on a trunk of a Narra tree. Photo: Courtesy of Rodolfo S. Treyes
Epiphytes are plants that depend on other plants for support. Usually, epiphytes grow on trunks and branches of trees. Figure 6 shows an epiphytic fern that attached itself on a trunk of a Narra tree without harming the tree. The Narra tree is a host that provides a place for the fern to live. When it rains, the ferns get nutrients from rotting leaves and other organic materials that collect at the root base of the fern plant. This relationship is called commensalism -- one organism benefits from the host organism, while the host organism is neither positively nor negatively affected. 117
Q25. What other examples of commensalism can you give? Figure 7 shows an insect larva and a leaf of a plant. What kind of relationship do you think do these two organisms have? Figure 7. A larva of an insect lives on the leaves of the plant and causes damage by eating the leaves.
Photo: Courtesy of Rodolfo S. Treyes
The insect larva (the parasite) gets its nutrients by eating the leaves – thereby, damaging the plant (the host). This relationship is called parasitism. A parasite gets its nutrients from a living host harmed by the interaction. Another example of parasitism is the flea that thrives on a dog. The dog is harmed by the flea that feeds on its blood. Q26. What other examples of parasitism can you give?
Activity 3 Which eats what? Objectives In this activity, you should be able to: 1. identify the predators and prey animals in the environment, 2. describe how the predators capture the prey animals for food, and 3. describe how predators and prey animals interact with each other in
the environment. Materials Needed
worksheet pencil hand lens
Procedure 1. Observe each organism in the picture carefully. Fill in the appropriate box to each of the organism. 118
Organisms
Q27. What organisms are involved?
Q28. Which is the eater? Which is eaten?
Q29. Which part of the body does the eater use to get its food?
2. You may visit a school ground or garden to make more observations.
119
3. If you have observed other organisms that are not in the list, you may also add such observations to your worksheet. No need to put pictures; just write the common name of the organisms on the appropriate box.
Organisms
Q30. Which organisms are involved?
Q31. Which is the eater? Which is eaten?
Q32. How does the eater get its food?
Animals kill and eat other animals. This interaction is called predation. An animal that kills and eat other animals is called a predator. An animal that is killed and eaten by its predator is called a prey. Prey animals are usually smaller and less powerful than the predator that eats them. In a given community, predators compete with other predators for prey animals. In the wild, a predator’s prey may be another prey’s predator. This means that while an animal hunts and feeds upon another animal, it can also become prey to a larger and stronger predator. When two populations use the same resource, they participate in a biological interaction called competition. Resources for which different populations compete include food, nesting sites, habitat, light, nutrients, and water. Usually, competition occurs for resources in short supply.
Energy Transfer in the Ecosystems Why does an organism eat another organism? Plants, animals, and microorganisms must obtain energy to enable them to move, grow, repair damaged body parts, and reproduce. 120
Plants are capable of converting energy from the Sun into chemical energy in the form of glucose (food). The process is called photosynthesis; it uses water, carbon dioxide, and sunlight. Most plants make much more food each day than they need. Excess glucose is converted into starch by the plants and is stored either in the roots, stem, leaves, tubers, seeds, or in fruits, as shown in Figure 8. Q33. Why are plants considered producers? Q34. Are plants the only organisms in an ecosystem that can produce their own food?
rice grains
“petchay”
corn grains
banana
“kamote”
potato
coconut
mango
cassava
sugar cane
Photos: Courtesy of Rodolfo S. Treyes
Figure 8. Different plant parts that store chemical energy in the form of starch or sugar. Sugar cane is an example of plant with high sugar content. There are also microorganisms that can photosynthesize; examples of which are shown in Figure 9.
Spirogyra (algae)
Cyanobacteria (anabaena)
Euglena
Diatoms
Figure 9. These photosynthetic microorganisms are present in ponds, in rice paddies, or any fresh water ecosystem. Q35. How do animals and humans obtain energy to keep them alive? Humans and other animals are not capable of making their own food. They are dependent on the organic matter made by photosynthetic organisms. These organisms that include the plants and some microorganisms are considered as producers.
121
Animals and humans must eat either plants or other animals to obtain energy. Organisms that feed on other organisms are called consumers. Those that get their energy by eating plants only are called first order consumers. Q36. Q37. Q38.
In figure 10, which organisms are being eaten? Which organisms are the consumers? In your community, what other organisms do you know eat plants only?
Goats eating grass
Cows eating grass
Caterpillar eating a leaf
Mouse eating corn
Figure 10. The first-order consumers are the animals that eat plants. Some energy in the first-order consumer is not used by the consumer itself. This energy is made available to another consumer. A consumer that eats the planteaters for energy is called a second-order consumer, examples of which are shown in figure 11.
Snake eats corn-eating mouse
Chicken eats caterpillar
Figure 11. The second-order consumers are the animals that eat the plant-eaters. Q39.
In figure 11, which organisms provide energy to the snake and chicken?
A second-order consumer gets only a fraction of energy from the first-order consumer that it fed upon. A part of this energy is stored and may be passed on to another consumer. A consumer that eats a second-order consumer is called a thirdorder consumer, examples of which are shown in figure 12. Human beings are thirdorder consumers.
122
Figure 12. Third-order consumers are organisms that eat the second-order consumers. (A) A hawk eats a chicken; and (B) a crocodile eats a chicken, too.
A Q40.
B
Refer to figure 13 below. How does energy from the Sun reach the thirdorder consumers? Trace the flow of energy among organisms by filling up the boxes below. The arrow ( ) pointing to the next box means “eaten by”.
Figure 13. Tracing the flow of energy from the Sun to different organisms. The transfer of energy can be sequenced. The sequence of energy transfer among organisms to obtain energy and nutrients is called a food chain (see figure 13). A food chain starts with the energy source, the Sun. The next link in the chain is the group of organisms that make their own food – the photosynthetic organisms (producers). Next in the sequence are the organisms that eat the producers; they are the first-order consumers. The next link in the chain is the group of animals that eat the first-order consumers; they are the second-order consumers. These organisms, in turn, are eaten by larger animals – the predators; they are also called, third-order consumers. Each food chain ends with a top predator – an animal with no natural enemies.
123
Photos: Courtesy of Grace Reyes and Rodolfo S. Treyes
Figure 14. A transfer of energy shown in a food chain. The “gabi” plant produces its own food through photosynthesis. Grasshopper eats the leaves of “gabi” plant to get its energy and nutrients. The chicken eats the grasshopper. Then the chicken is eaten by humans. Q41.
List down the organisms found in your community. Classify them according to the following categories:
Organism
Q42.
Producer
First-Order Consumer
Second-Order Consumer
Third-Order Consumer
Construct a food chain using the organisms listed on the table above.
When plants and animals die, the energy in their bodies can be transferred to another group of organisms. Consumers that look for and eat dead animals or plants are considered scavengers. House flies, cockroaches, maggots and ants are scavengers (see figure 15). Earthworms feed on dead grass and leaves if they are above ground. They also feed on fruits, berries, and vegetables. If they are under the soil, earthworms may feed on algae, fungi, and bacteria.
124
Photos: Courtesy of Rodolfo S. Treyes
Figure 15. Common scavengers: housefly, earthworm, ants, and cockroach. Once the scavengers are done with eating a dead organism, the decomposers (microorganisms) take over and consume whatever was left by the scavengers. Decomposers consume any dead plants and animals. There are different kinds of decomposers performing different functions in the ecosystem. Some groups of bacteria prefer breaking down meat or waste from the consumers that eat meat.
Figure 16. A group of bacteria.
What do you see on bread or rice that had been kept for some time? They have molds! Sometimes, you see a trunk of a tree with mushrooms growing on it (refer to figure 17). These are fungi and they are decomposers; they prefer to grow on starchy food, fruits, vegetables, and dead plants.
Photos: Courtesy of Rodolfo S. Treyes
Figure 17. Fungi growing on leftover rice and bread, fruit, and dead trunk of a tree. 125
Microorganisms that include bacteria and fungi break down proteins, starches, and other complex organic substances that were once part of living things. During the process of decomposition, decomposers release nutrients from the organic material back into the soil, making the soil available to plants and other producers.
Activity 4 What to do with food wastes? At the end of this activity you will decide on the best way to deal with food wastes in your home or school. You will record your observations and draw inferences. You will construct food chains starting with the food wastes, which are actually dead organisms, and the living organisms found in the compost pots. You will supplement your observations and inferences with information found from the internet or in the library.
Materials Needed
Two small, clear jars with covers (and with holes all over) At least three large clay flower pots, Soil Rubber gloves Trowel Microscope Slides and cover slips Magnifying lens Pole for aerating composting materials Wire covers for the clay pots
Procedure 1. Set up the composting pots and jars in advance. In one covered jar, put some food wastes. In the other covered jar, put a layer of soil at the bottom, followed by a layer of food wastes covered with a layer of soil. Repeat until the jar is full. Do the same for the clay pots, filling one first before moving to the second pot, until the third (or last pot) is full. Water the jar and pots with soil if the soil dries up. 2. Do not water the jar of food wastes without soil. Observe the food wastes and living organisms that you find in the jar daily. Record your observations on a table like the one below:
126
Day/Date
Observations about food wastes and living organisms
Note: Write your answers on your notebook. Add rows as needed. 3.
Do the same for the jar with soil and the clay pots as soon as they are full. Include observations about the soil.
4.
After a week, and every week thereafter, mix the contents of a clay pot to provide air to the organisms underneath the surface the soil.
5.
Continue your observations until the food wastes can no longer be seen and everything looks like soil. This means that decomposition of the food wastes is complete or nearly so. You have made compost.
Q43.
What organisms did you find in the compost jar or pot from Day 1? List them down in the order of appearance. You may draw those you cannot identify. (Write your answers on your notebook.)
Use the magnifying lens and microscope to examine very small and microscopic organisms. On Day 1, get small samples of the soil and make wet mounts to examine it under the microscope. Repeat this after a week and every week thereafter until the observations are concluded. Q44.
Draw the microscopic organisms you observe and try to identify them with the help of reference books.
Q45.
Construct at least one food chain and one food web based on your observations.
Q46.
What is the benefit of composting food wastes?
Q47.
What other methods would you recommend to dispose of food wastes?
Energy transfer in an ecosystem follows a process. The ultimate source of energy for all living things is the Sun. The producers of the ecosystem take energy from sunlight and convert it to chemical energy. This energy is passed on to consumers and then to decomposers. The energy flows only in one direction and is not cycled back. In contrast, the materials in the form of nutrients needed by living things are cycled between organisms and the environment. These materials are used up by the producers to make other forms of materials that are cycled among the consumers and finally returned to the environment by the decomposers. Energy flows and materials are cycled in the ecosystem. We live in a dynamic world, indeed!
127
Reading Materials/Links/Websites About Our Earth, Panda. (2008). Ecological interactions. Teacher Resources, Web Fieldtrips. Retrieved from http://wwf.panda.org/ Global Change, University of Michigan. (2008). Ecological communities: networks of interacting species. Global Change Lectures. Retrieved from http://www.globalchange.umich.edu/ Johnson, George B., & Raven, Peter H. Biology. Holt, Rinehart & Winston: A Harcourt Education Company, U.S.A. 2004 Nature, International Weekly Journal of Science. (2010). Ecological interactions. Nature Journal. Retrieved from http://www.nature.com/nature/index.html Reece, Jane B., et al. Campbell Biology: Concepts and Connections, 7th ed. Pearson Education Inc., U.S.A. 2012
128
129
130
Suggested time allotment: 8 to 10 hours
Unit 3 MODULE
1
DESCRIBING MOTION
Many of the things around us move. Some move slowly like the turtles and clouds, others move much more quickly like the satellites. Because motion is so common, it seems to be very simple. But in science, describing motion actually entails careful use of some definitions. This module provides you with scientific knowledge and skills necessary to describe motion along a straight path. You will learn to describe the motion of objects in terms of position, distance travelled, and speed. You will also learn to analyze or represent motion of objects using charts, diagrams, and graphs. While these all provide the same information about the motion of objects, you will find out that one may be more helpful than the other depending on your particular objective.
At the end of this module, you are expected to answer the following questions:
When can we say that an object is in motion? How do we describe the motion of an object?
Where? Before you will be able to describe the motion of an object, you must first be able to tell exactly where it is positioned. Describing exact position entails two ideas: describing how far the object is from the point of reference and describing its direction relative to that point of reference. You will learn about the importance of point of reference and direction when you perform Activity 1.
131
Activity 1 Where is it? Objective In this activity, you should be able to describe in words the position of an object within the room or the school ground.
Procedure 1.
Obtain from your teacher the piece of paper that describes where you will find the object.
Q1. Were you able to find the object? Was it easy or difficult? Q2. Is the instruction clear and easy to follow? What made it so? 2.
Put back the object to its place, if you found it. Otherwise, ask your teacher first where it is located before you move on to the next step.
3.
Revise the instruction to make it more helpful. Write it on a separate sheet of paper and let another group use it to find the object.
Q3. Were they successful in finding the object? Was it easy for them or difficult? Q4. What other details or information included in your instruction that made it clearer and easier to follow? Q5. In your own words, what is point of reference and how important it is? Describing through visuals The position of an object can be described in many ways. You can use words, like what you did in Activity 1. You can also use visuals, like diagrams or graphs. Use the examples to explore how these help in providing accurate descriptions of positions of objects. Using diagrams Consider the diagram in Figure 1. The positions of the objects are described in the diagram by their coordinates along the number line.
-15m
-10m
- 5m
0m Figure 1
132
5m
10m
15m
Q6. Q7. Q8. Q9.
What is the position of the dog? What is the position of the tree? What is the position of the dog with respect to the house? What is the position of the tree with respect to the dog?
Here is another example. In this diagram, the positions of the ball rolling are shown at equal intervals of time. You can use the diagram to describe the position of the ball at any given time. (Timer)
00 : 00
min
00 : 05
sec
min
0m
00 : 10
sec
min
5m
sec
10m
00 : 15
min
sec
15m
Figure 2 Q10. What is the initial position of the ball? What is its final position? Q11. What is the position of the ball at 10 seconds? Q12. At what time is the position of the ball equal to 5 meters?
Using graphs Another way to describe the motion of the ball is by the use of motion graphs. Convert the diagram in Figure 2 to graph by following the guide below. I.
Fill up Table 1 using the data in Figure 2. Note that the positions of the ball are shown every 5 seconds. Table 1: Position of the ball vs time Time (s) 0
Position of the ball (m) 0
II. Plot the values in Table 1 as points on the graph in Figure 3. Note that time is plotted on the X-axis while position is plotted on the Y-axis. An example is given below.
133
Position (m)
15
10
5
(20s, 5m)
0
5
10
15
20 Time (s)
Figure 3
III. Lastly, draw a straight diagonal line through the points in the graph.
The graph that you have just drawn in Figure 3 is called position-time graph. You can also use this graph to describe the position of the ball at any given time. For example, if you are asked to find the position of the ball at 10 seconds, all you need to do is to find the point along the diagonal line where the vertical line at the 10 second-mark intersects (Figure 4). Then find where the horizontal line from that point of intersection will cross the Y axis, which is the position axis. This will give you the position of the ball at 10 seconds.
Position (m)
Point of intersection
0
10
Figure 4 134
Time (s)
Now try answering the following questions using your own position-time graph. Q13. What is the position of the ball at 7.5 seconds? Q14. At what time is the position of the ball equal to 12.5 meters?
How Far? In science, motion is N defined as the change in position E W for a particular time interval. You can then start describing motion 10m S 5m with the question, “How far did the object travel?” There are actually 10m two ways to answer this question. First is by getting the total length of the path travelled by the object. In Figure 5 for example, the dog ran 10m to the east, then 5m to Figure 5 the south, and another 10m to the west. So it has travelled a total of 25 meters. The other way is by measuring the distance between the initial position and final position of the object. Based again on Figure 5, the dog has travelled 5 meters to the south. In science, the first measurement gives the distance travelled by the object (represented by broken lines) while the second measurement gives its displacement (represented by continuous line). Here are more illustrations showing the difference between distance travelled (represented by broken lines) by an object and its displacement (represented by continuous lines).
a. b.
c. Figure 6 135
Can you give one difference between distance and displacement based on the given examples? When can displacement be equal to zero? Is it possible to get zero displacement? What if the ball, the car, and the dog in the illustration go back to their starting positions, what will happen to their respective distances? How about their displacements? If you answered these questions correctly, then you have most probably understood the difference between distance and displacement.
Distance refers to the length of the entire path that the object travelled. Displacement refers to the shortest distance between the object’s two positions, like the distance between its point of origin and its point of destination, no matter what path it took to get to that destination.
When a graph is plotted in terms of the distance travelled by the object and the time it took to cover such distance, the graph can be called distance-time graph. If the graph is plotted in terms of displacement and time, it is called displacementtime graph. Refer to the graph in Figure 7. What is the displacement of the object after 2 seconds? What is its displacement after 6 seconds? How will you describe the motion of the object between 0s and 2s, between 2s and 4s, and between 4s and 6s?
Displacement (m)
4 3 2 1 0 1
2
3
Figure 7
136
4
5 6 Time (s)
Activity 2 My home to school roadmap Objective In this activity you should be able to make a roadmap that shows how you get to school from your house.
Procedure 1. 2.
3.
Devise a way to easily measure distance. Let your teacher check your nonstandard measurement for precision. Using your measuring device, gather the data that you will need for your roadmap. Make sure that you take down notes of all names of the roads, landmarks, corners, posts, and establishments you pass by. Record your data properly. Using your gathered data, draw your house-school roadmap on a short bond paper. Decide on the most convenient scale to use when you draw your roadmap. An example is shown below. 1 cm
Scale: 1 cm = 1 km 5 km
2 km
3 km Figure 8 4.
Label your roadmap properly, including names of the roads, establishments, etc. Specify also the length of road. 5. Finally, let your teacher check again your work. Q1. What is the total length of your travel from your house to your school? Q2. What is the total displacement of your travel?
How fast? After determining how far the object moves, the next question will be “How fast did the object move?” This information can be provided by the object’s speed or velocity. Are you familiar with the traffic signs below? These signs tell us the maximum or minimum speed limits allowed by law for road vehicles. In general, the minimum speed limit in the Philippines is 60 km/h and the maximum speed limit is 100 km/h. What are the units used in the above examples of speed limits? What quantities do these units represent that are related to speed? 137
Activity 3 Fun walk Objective In this activity you should be able to gather data to determine who walks fastest.
Procedure 1. Start by choosing a spacious place to walk straight. 2. Half of the group will walk while the other half will observe and record data. 3. Mark on the ground the starting line. All participants must start from the starting line at the same time. 4. Upon receiving the go signal, all participants must start to walk as fast as they could. The other members should observe closely as the participants walk and determine who walks fastest. 5. Repeat #4 but this time, collect data to support your conclusion. Discuss within your group how you are going to do this. Q1. What quantities did you measure for your data? Q2. How did you combine these quantities to determine how fast each participant was walking? Q3. How did you use the result to determine who walked fastest? Speed The questions in the above activity are actually referring to speed. If you know the speed of each participant, you can tell who is the fastest. Speed is defined as distance travelled divided by the time of travel.
speed
distance travelled time of travel
The units of speed can be miles per hour (mi/h), kilometres per hour (km/h), or meters per second (m/s). Q4. At constant distance, how is speed related to the time of travel? 138
Q5. At constant time to travel, how is speed related to the distance travelled? Q6. Who was travelling faster than the other, a person who covered 10 meters in 5 seconds or the one who took 10 seconds to cover 20 meters? Speed and direction In describing the motion of an object, we do not just describe how fast the object moves. We also consider the direction to where it is going. Speed with direction is referred to as velocity. The sample weather bulletin below will show you the importance of knowing not just the speed of the storm but also its direction.
Table 2: Sample weather bulletin Weather Bulletin: Tropical Storm "Juaning" Wednesday, 27 July 2011 at 09:27:14 AM Location of 90 km East of Infanta, Center Quezon Coordinates 14.8°N, 122.5°E Strength of the winds Movement
Max. wind speed of 85 km/hr near the center & gustiness of up to 100 km/hr
Forecast
On Wednesday AM: Expected to make landfall over Polillo Island between 8am to 10am and over Southern Aurora by 1pm to 3pm and will traverse Central Luzon
11km/hr going West-Northwest
Whenever there is a storm coming, we are notified of its impending danger in terms of its speed and direction. Aside from this, we are also informed about its strength. Do you know that as the storm moves, its winds move in circles? The circular speed of the winds of the storm determines its strength. Different storm signals are given in places depending on the circular speed of the winds of the storm and the distance from the center. Study again the weather bulletin above. Which is the speed for the circular motion of the typhoon winds? Which is the speed for the motion of the storm as a whole along the path? How important are speed and direction in determining the weather forecast for the next hours? Constant speed vs instantaneous speed 139
If you solved for the distance travelled by each participant over the time he took to cover such distance, then you have computed for his average speed. But why average speed and not just speed? It is considered average speed because it represents the speed of the participant throughout his travel. During his travel, there were instants that his speed would vary. His speed at an instant is called instantaneous speed. Similarly, the velocity of a moving body at an instant is called instantaneous velocity. The instantaneous speed may be equal, greater than, or less than the average speed. When an object’s instantaneous speed values are always the same, then it means that the object is moving with constant speed. We refer to this as constant motion. Where you will be and what time you will reach your destination is easily predicted when you move at constant speed or velocity. Are you familiar with the speedometer? Speedometer is a device used to measure the instantaneous speed of a vehicle. Speedometers are important to the drivers because they need to know how fast they are going so they know if they are already driving beyond the speed limit or not.
How fast is the velocity changing?
Source: http://drrm.region4a.dost.gov.ph/
Figure 9. Track of tropical storm “Juaning” In reality, objects do not always move at constant velocity. Storms like “Juaning” also do change their speeds, directions, or both. The next activity will help you analyze examples of motion with changing velocities (or with changing speed, since we are only trying to analyze examples of motion in only one direction) using tape charts and motion graphs.
140
Activity 4 Doing detective work Consider this situation below: Supposed you were having your on-the-job training in a private investigating company. You were asked to join a team assigned to investigate a ‘hit and run’ case. The alleged suspect was captured by the CCTV camera driving down a road leading to the place of incident. The suspect denied the allegation, saying that he was then driving very slowly with a constant speed. Because of the short time difference when he was caught by the camera and when the accident happened, he insisted that it was impossible that he would already be at the place when the crime happened. But when you were viewing the scene again on the camera, you noticed that his car was leaving oil spots on the road. When you checked these spots on site, you found out that they are still evident. So you began to wonder if the spots can be used to investigate the motion of the car of the suspect and check whether he was telling the truth or not. Here is an activity that you can do to help you with your investigation. You will analyze the motion using strips of papers with dots. For this activity, assume that the dots represent the ‘oil drops’ left by the car down the road.
Materials
ruler paper strips with dots cutter or pair of scissors
Procedure A. Using tape chart 1. 2.
Obtain from your teacher paper strips with dots. Label each dot. Start from 0, then 1, 2, 3, and so on. In this example, each dot occurred every 1 second. 1 sec
0
1
2
3 Figure 10
3.
Examine the distances between successive dots.
Q1. How will you compare the distances between successive dots?
141
4.
Cut the strip at each drop, starting from the first to the last drop, and paste them side by side on a graph paper to form a tape chart as shown in Figure 11.
4 3
Q2. How do the compare?
lengths
of
the tapes 2
Q3. If each tape represents the distance travelled by the object for 1 second, then what ‘quantity’ does each piece of tape provide?
1
Figure 11. Sample tape chart
Q4. What does the chart tell you about the speed of the car? The difference in length between two successive tapes provides the object’s acceleration or its change in speed or velocity for a time interval of 1 second. Q5. How will you compare the changes in the lengths of two successive tapes? Q6. What then can you say about the acceleration of the moving car? B. Using motion graphs 5.
Measure the distance travelled by the car after 1 second, 2 seconds, and so on by measuring the distance between drops 0 and 1, 0 and 2, and so on. Enter your measurements in Table 3 on the right. Table 3 Time of travel (s)
Distance travelled (m)
1 2 3 4 5
6.
Plot the values in Table 3 as points on the graph in Figure 12 on the right.
Q7. How does your distance-time graph look like?
142
Distance (cm) 0 Time (sec)
Figure 12
Join the mid-points of the tops of the tapes with a line. You have now converted your tape chart to a speed-time graph.
Q8. How does you graph look like? How is this different from your graph in Figure 12?
4
Speed (cm/s)
7.
3 2 1
Q9. How will you interpret this graph in terms of the speed and acceleration of the moving car?
1
2
3
4
Time (s)
Figure 13
Q10. If you found out in your investigation that the arrangement of oil drops left by the car is similar to what you used in this activity, was the suspect telling the truth when he said that he was driving with constant speed?
In this module, you have learned how to describe the motion of objects in terms of position, distance and displacement, speed and velocity, and acceleration. You have also learned how to represent motion of objects using diagrams, charts, and graphs. Let us summarize what you have learned by relating distance, displacement, speed, velocity, and acceleration.
If an object does not change its position at a given time interval, then it is at rest or its speed is zero or not accelerating.
143
If an object covers equal distance at equal intervals of time, then it is moving at constant speed and still not accelerating.
If an object covers varying distances at equal intervals of time, then it is moving with changing speed or velocity. It means that the object is accelerating.
Links and References Chapter 2: Representing Motion. Retrieved March 14, 2012 from http://igcse-physics-41-p2-yrh.brentsvillehs.schools.pwcs.edu/modules Chapter 3: Accelerated Motion. Retrieved March 14, 2012 from http://igcse-physics-41-p2-yrh.brentsvillehs.schools.pwcs.edu/modules HS Science IV: Physics in your environment. Teacher’s Edition. 1981. Science Education Center. Quezon City
144
Suggested time allotment: 4 to 5 hours
Unit 3 MODULE
2
WAVES AROUND YOU
Waves occur all around you in the physical world. When you throw a stone into a lake, water waves spread out from the splash. When you strum the strings of a guitar, sound waves carry the noise all around you. When you switch on a lamp, light waves flood the room. Water, sound, and light waves differ in important ways but they all share the basic properties of wave motion. For instance, you can see water waves and surfers would say that they enjoy riding the waves. On the other hand, you don’t see sound waves and light waves but you experience them in other ways. Your ears can detect sound waves and your skin can get burned by ultraviolet waves if you stay under the sun for too long. A wave is a periodic disturbance that moves away from a source and carries energy with it. For example, earthquake waves show us that the amount of energy carried by a wave can do work on objects by exerting forces that move objects from their original positions. Have you personally experience an earthquake? How did it feel? Did you know that you can understand earthquakes by studying waves? In this module, you would be doing three activities that would demonstrate the properties of wave motion. After performing these activities, you should be able to:
1. explain how waves carry energy f rom one place to another; 2. dist inguish bet ween transverse and longitudinal waves; 3. dist inguish bet ween mechanical and electromagnet ic waves; and 4. create a model to demonstrate the relationshi p among f requency, amplit ude, wavelengt h, and wave velocit y.
145
Warm up. What are Waves? Activity 1 will introduce you to different types of waves distinguished according to the direction of vibrations of p articles with respect to the direction in which the waves travel. Activity 2 will give you a background of the terms and quantities used in describing periodic waves. Finally, Activity 3 will strengthen your understanding of the properties of waves and how they propagate. Try to wave at your seatmate and observe the motion of your hand. Do you make a side-to-side motion with the palm of your hand? Do you do an up-and-down motion with your hand? 1.
Describe your personal hand wave.
The repetitive motion that you do with your hand while waving is called a vibration. A vibration causes wave motion. When you observe a wave, the source is always a vibration. 2.
Think of a still lake. How would you generate water waves on the lake?
Waving is a common gesture that people do to catch someone’s attention or to convey a farewell.
Activity 1. Let’s make waves! What happens when waves pass by? Objective In this activity, you will observe and draw different types of waves and describe how they are produced. You will also describe the different types of waves.
Time Allotment: 30 minutes Materials
A rope (at least five meters long) A colored ribbon A coil spring (Slinky™) A basin filled with water A paper boat
146
Procedure A.
What are transverse waves? 1.
Straighten the rope and place it above a long table. Hold one end of the rope and vibrate it up and down. You would be able to observe a pulse. Draw three sketches of the rope showing the motion of the pulse at three subsequent instances (snapshots at three different times). Draw an arrow to represent the direction of the pulse’s motion. Time 1
Time 2
Time 3
a.
What is the source of the wave pulse?
b.
Describe the motion of your hand as you create the pulse.
c.
Describe the motion of the pulse with respect to the source.
You will now tag a specific part of the rope while making a series of pulses. A periodic wave can be regarded as a series of pulses. One pulse follows another in regular succession.
Figure 1. Periodic wave
147
Tie one end of the rope on a rigid and fixed object (e.g heavy table, door knob, etc).
Figure 2. Rope tied to a rigid object Attach a colored ribbon on one part of the rope. You may use adhesive tape to fix the ribbon. Make a wave by continuously vibrating the end of the rope with quick up-and-down movements of your hand. Draw the waveform or the shape of the wave that you have created.
Ask a friend to vibrate the rope while you observe the motion of the colored ribbon. Remember that the colored ribbon serves as a marker of a chosen segment of the rope.
B.
a.
Does the wave transport the colored ribbon from its original position to the end of the rope?
b.
Describe the vibration of the colored ribbon. How does it move as waves pass by? Does it move in the same direction as the wave?
What are longitudinal waves? 1.
Connect one end of a long table to a wall. Place coil spring on top of table. Attach one end of the coil spring to the wall while you hold the other end.
148
Figure 3. Coil spring on a flat table with one end attached to a wall Do not lift the coil spring. Ask a friend to vibrate the end of the coil spring by doing a back-and-forth motion parallel to the length of the spring. Observe the waves along the coil spring. Draw how the coil spring looks like as you move it back-and-forth.
2.
Attach a colored ribbon on one part of the coil spring. You may use an adhesive tape to fix the ribbon. Ask a friend to vibrate the coil spring back-and-forth while you observe the motion of the colored ribbon. Remember that the colored ribbon serves as a marker of a chosen segment of the coil spring. a. Does the wave transport the colored ribbon from its original position to the end of the rope? b. Describe the vibration of the colored ribbon. How does it move as waves pass by?
C.
What are surface waves? 1.
Place a basin filled with water on top of a level table. Wait until the water becomes still or motionless. Create a wave pulse by tapping the surface of the water with your index finger and observe the direction of travel of the wave pulse. Tap the surface of the water at regular intervals to create periodic waves. View the waves from above and draw the pattern that you see. In your drawing, mark the source of the disturbance.
149
2.
Wait for the water to become still before you place your paper boat on the surface. Create periodic waves and observe what happens to your paper boat. a. Do the waves set the paper boat into motion? What is required to set an object into motion? b. If you exert more energy in creating periodic waves by tapping the surface with greater strength, how does this affect the movement of the paper boat?
3.
If you were somehow able to mark individual water molecules (you used a colored ribbon to do this earlier) and follow them as waves pass by, you would find that their paths are like those shown in the figure below.
Water molecules move in circular orbits when waves passes by
Figure 4. Surface waves a. As shown in the figure, the passage of a wave across a surface of a body of water involves the motion of particles following a ___________ pattern about their original positions. b. Does the wave transport water molecules from the source of the vibration? Support your answer using the shown figure. D.
Summary 1.
Waves can be typified according to the direction of motion of the vibrating particles with respect to the direction in which the waves travel. a. Waves in a rope are called ____________ waves because the individual segments of the rope vibrate ____________ to the direction in which the waves travel. b. When each portion of a coil spring is alternatively compressed and extended, ____________ waves are produced. c. Waves on the surface of a body of water are a combination of transverse and longitudinal waves. Each water molecule moves in a _______________ pattern as the waves pass by. 150
2.
How do we know that waves carry energy?
3.
What happens when waves pass by?
Activity 2. Anatomy of a Wave How do you describe waves? Background You had the experience of creating periodic waves in Activity 1. In a periodic wave, one pulse follows another in regular succession; a certain waveform – the shape of individual waves – is repeated at regular intervals. Most periodic waves have sinusoidal waveforms as shown below. The highest point and lowest point of a wave are called the crest and the trough respectively. The amplitude is the maximum displacement of a vibrating particle on either side of its normal position when the wave passes.
Figure 5. Sinusoidal wave
Objective In this activity, you will identify the quantities used in describing periodic waves.
Time Allotment: 40 minutes Materials
A ruler A basin filled with water A rope (at least five meters long) A colored ribbon A watch or digital timer 151
Procedure A.
How can you measure the wavelength of a wave? 1.
The wavelength of a wave refers to the distance between any successive identical parts of the wave. For instance, the distance from one crest to the next is equal to one full wavelength. In the following illustration, this is given by the interval B to F. Identify the other intervals that represent one full wavelength.
__________________________________________________________ __________________________________________________________ 2.
Place a basin filled with water on top of a level table. Wait for the water to become still. Create a vibration by regularly tapping the surface of the water with your index finger. You would be able to see the subsequent crest of the water waves.
Figure 6. Crest and trough on a water wave Draw the water waves as you see them from the top of the basin. Label one wavelength in your drawing.
152
3.
Increase the rate of the vibrations you create by tapping the surface of the water rapidly. What happens to the wavelength of the waves? Draw the water waves as you see them from the top of the basin. Compare it with your drawing in number 2.
B.
How do you measure the frequency of a wave? 1.
The frequency of a series of periodic waves is the number of waves that pass a particular point every one second. Just like what you have done in Activity 1, attach a colored ribbon on a rope to serve as a tag. Tie one end of the rope on a fixed object and ask a friend to create periodic waves by regularly vibrating the other end of the rope.
2.
You will count how many times the colored ribbon reached the crest in 10 seconds. You will start counting once the ribbon reaches the crest a second time. It means that one wave has passed by the ribbon’s position. Ask another friend with a watch or a digital timer to alert you to start counting and to stop counting after 10 seconds. Record the results in Table 1.
3.
It is also useful to consider the period of a wave, which is the time required for one complete wave to pass a given point. The period of each wave is
From the identified frequency of the observed periodic waves, the period can be calculated. For example, if two waves per second are passing by, each wave has a period of ½ seconds. Table 1. Frequency and period of the wave Number of waves Frequency (N cycles) that passed of the waves by the ribbon in 10 (N cycles/10 seconds) seconds
Period of the waves (seconds)
The unit of frequency is the hertz (Hz); 1 Hz = 1 cycle/second. 153
4.
C.
If you increase the frequency of vibration by jerking the end of the rope at a faster rate, what happens to the wavelength?
How do you measure the speed of a wave? 1.
Using the rope with ribbon. Create periodic waves and estimate their wavelength. Count the number of waves that pass by the ribbon in ten seconds. Compute the frequency of the waves. Record the results in Table 2.
2.
The wave speed is the distance traveled by the wave per second.
wave speed = distance traveled per second = frequency x wavelength From the basic formula that applies to all periodic waves, you can see that wave speed, frequency and wavelength are independent of the wave’s amplitude. a. Using the data from number 1, calculate the wave speed of the observed periodic waves. Record the result in Table 2. Table 2. The speed of a wave Number of waves Estimated (N cycles) that wavelength passed by the (meters) ribbon in 10 seconds
Frequency of the waves (N cycles/10 seconds)
Wave speed (meter/second)
Summary 1.
What is the relationship between wave speed, wavelength and frequency?
2.
Suppose you observed an anchored boat to rise and fall once every 4.0 seconds as waves whose crests are 25 meters apart pass by it. a. What is the frequency of the observed waves? b. What is the speed of the waves?
154
Activity 3. Mechanical vs. Electromagnetic Waves How do waves propagate? Objective In this activity, you will differentiate between mechanical waves and electromagnetic waves.
Time Allotment: 30 minutes Materials A.
Findings from Activity 1 Chart of the electromagnetic spectrum What are mechanical waves? 1.
When you created waves using a rope in Activity 1 Part A, you were able to observe a moving pattern. In this case, the medium of wave propagation is the rope. a. In Activity 1 Part B, what is the medium of wave propagation? b. In Activity 1 Part C, what is the medium of wave propagation?
2.
The waves that you have created in Activity 1 all require a medium for wave propagation. They are called mechanical waves. a. How can you generate mechanical waves?
3.
The medium of propagation for the wave shown above is the rope.
All three kinds of waves – transverse, longitudinal, and surface – are sent out by an earthquake and can be detected many thousands of kilometers away if the quake is a major one. a. What do you think is the source of earthquake waves? b. What is the medium of propagation of earthquake waves?
155
B.
What are electromagnetic waves? 1.
Energy from the sun reaches the earth through electromagnetic waves. As opposed to mechanical waves, electromagnetic waves require no material medium for their passage. Thus, they can pass through empty space. Locate the electromagnetic spectrum chart in your classroom. A smaller image of the chart is shown below. Identify the common name of each wave shown in the chart. 1. _____________________
5. _____________________
2. _____________________
6. _____________________
3. _____________________
7. _____________________
4. _____________________ 2.
The electromagnetic spectrum shows the various types of electromagnetic waves, the range of their frequencies and wavelength. The wave speed of all electromagnetic waves is the same and equal to the speed of light which is approximately equal to 300 000 000 m/s.
Figure 7. The electromagnetic spectrum
a.
Examine the electromagnetic spectrum. 1.
Describe the relationship between frequency wavelength of each electromagnetic wave.
156
and
2.
Draw waves to represent each electromagnetic wave. Your illustrations must represent the wavelength of a wave relative to the others. For instance, gamma rays have a very small wavelength compared to the other waves in the spectrum.
1. Gamma Rays
2. __________
3. __________
4. __________
5. __________
6. __________
7. __________
b.
The Sun is an important source of ultraviolet (UV) waves, which is the main cause of sunburn. Sunscreen lotions are transparent to visible light but absorb most UV light. The higher a sunscreen’s solar protection factor (SPF), the greater the percentage of UV light absorbed. Why are UV rays harmful to the skin compared to visible light? Compare the frequency and energy carried by UV waves to that of visible light.
157
C.
Summary 1.
Mechanical waves like sound, water waves, earthquake waves, and waves in a stretched string propagate through a _______________ while __________________ waves such as radio waves, visible light, and gamma rays, do not require a material medium for their passage.
Review. Waves Around You The activities that you have performed are all about wave motion or the propagation of a pattern caused by a vibration. Waves transport energy from one place to another thus they can set objects into motion.
What happens when waves pass by? Activity 1 introduced you to transverse waves, longitudinal waves, and surface waves. You observed the motion of a segment of the material through which the wave travels. 1.
Transverse waves occur when the individual particles or segments of a medium vibrate from side to side perpendicular to the direction in which the waves travel.
2.
Longitudinal waves occur when the individual particles of a medium vibrate back and forth in the direction in which the waves travel.
3.
The motion of water molecules on the surface of deep water in which a wave is propagating is a combination of transverse and longitudinal displacements, with the result that molecules at the surface move in nearly circular paths. Each molecule is displaced both horizontally and vertically from its normal position.
4.
While energy is transported by virtue of the moving pattern, it is important to remember that there is not net transport of matter in wave motion. The particles vibrate about a normal position and do not undergo a net motion.
158
How can you describe waves? In Activity 2, you have encountered the important terms and quantities used to describe periodic waves. 1.
The crest and trough refer to the highest point and lowest point of a wave pattern, respectively.
2.
The amplitude of a wave is the maximum displacement of a particle of the medium on either side of its normal position when the wave passes.
3.
The frequency of periodic waves is the number of waves that pass a particular point for every one second while the wavelength is the distance between adjacent crests or troughs.
4.
The period is the time required for one complete wave to pass a particular point.
5.
The speed of the wave refers to the distance the wave travels per unit time. It is related to the frequency of the wave and wavelength through the following equation: wave speed = frequency x wavelength
How do waves propagate? Finally, Activity 3 prompted you to distinguish between mechanical and electromagnetic waves. 1.
In mechanical waves, some physical medium is being disturbed for the wave to propagate. A wave traveling on a string would not exist without the string. Sound waves could not travel through air if there were no air molecules. With mechanical waves, what we interpret as a wave corresponds to the propagation of a disturbance through a medium.
2.
On the other hand, electromagnetic waves do not require a medium to propagate; some examples of electromagnetic waves are visible light, radio waves, television signals, and x-rays.
159
References and Web Links Anatomy of an electromagnetic wave. Available at: http://missionscience.nasa.gov/ems/02_anatomy.html Electromagnetic waves. Available at: http://www.colorado.edu/physics/2000/waves_particles/ [3] Hewitt, P. (2006). Conceptual Physics 10th Ed. USA: Pearson Addison-Wesley. The anatomy of a wave. Available at: http://www.physicsclassroom.com/class/waves/u10l2a.cfm The nature of a wave. Available at: http://www.physicsclassroom.com/class/waves/u10l1c.cfm
160
Suggested time allotment: 8 to 10 hours
Unit 3 MODULE
3
SOUND
Would you like to try placing your palm on your throat while saying – “What you doin?” What did your palm feel? Were there vibrations in the throat? Try it again and this time, say – “Mom! Phineas and Ferb are making a title sequence!” In the previous module you learned about wave properties and common characteristics like pitch and loudness. You will also learn the 2 kinds of waves according to propagation. These are the longitudinal and transverse waves. Sound is an example of a longitudinal wave. It is also classified as a mechanical wave. Thus there has to be matter for which sound should travel and propagate. This matter is better known as medium.
Terms to Remember Longitudinal Wave - Wave whose motion is parallel to the motion of the particles of the medium Mechanical wave - Wave that need a medium in order to propagate
Figure 1. Longitudinal wave
How does sound propagate?
In Activity 1, you will try to explore how sound is produced. You are going to use local materials available in your community to do this activity. You can do “Art Attack” and be very creative with your project.
161
Activity 1 My own sounding box Objectives In this activity, you should be able to construct a sounding box to 1.
demonstrate how sound is produced; and
2.
identify factors that affect the pitch and loudness of the sound produced.
Materials Needed
shoe box variety of elastic or rubber bands (thin and thick) extra cardboard – optional pair of scissors or cutter ruler
TAKE CARE!
Handle all sharp tools with care.
Procedure 1.
Cut and design your shoe box as shown in Figure 2.
2.
Put the rubber bands around the box. Make sure that the rubber bands are almost equally spaced and that the rubber bands are arranged according to increasing thickness from the lower end to the other end of the box.
3.
Use your finger to pluck each rubber band. Listen to the sound produced. Figure 2. My sounding box Q1.
What physical signs did you observe when you plucked each band. Did you hear any sound? What produced the sound?
162
Q2.
4.
This time use the fingers of one hand to stretch one of the elastics. Pluck the elastic with the fingers of the other hand and observe. Q3.
5.
How different are the sounds produced by each band with different thickness?
Are there changes in the note when you plucked the stretched band?
Repeat step 4 with the other elastic bands. Q4.
Arrange the elastics in sequence from the highest note to the lowest note produced.
When we talk or make any sound, our vocal cords vibrate. When there are no vibrations felt, no sound is produced. This means that sounds are caused by vibrations. Vibrations of molecules are to the to-and-fro or back-and-forth movement of molecules. Vibrations are considered as a disturbance that travels through a medium. This vibratory motion causes energy to transfer to our ears and is interpreted by our brain. Sound waves are examples of longitudinal waves. They are also known as mechanical waves since sound waves need medium in order to propagate. In Activity 1, vibrations produced by the elastic band produced sound. The sounding box amplified (increase in amplitude) this sound. Sound waves can travel in air. When they come in contact with our eardrums, the vibrations of the air force our eardrums to vibrate which is sensed and interpreted by our brain. Can sound waves also travel in other media like solids and liquids?
You can try this one. Place your ear against one end of a tabletop. Ask a friend to gently tap the other end of the table with a pencil or a ruler. What happens? Then ask your friend to again gently tap the other end of the table but this time, make sure that your ear is not touching the table. What happens? In which situation did you encounter louder and more pronounced sound? In which situation did you encounter the sound clearly? Sound is produced by the slight tapping of the table with a pencil or a ruler. This can be heard clearly at the other end of the table. This shows that sound waves can also travel through wood or solid. Sound is more distinct in solids than in air. This also means that sound is heard much louder when it travels in solids than in air.
163
What about in liquids? Can sound travel in liquids too? Liquids are better transmitters of sound than gases. If two bodies are struck together underwater, the sound heard by a person who is underwater is louder than when heard in air, but softer than in solids.
Figure 3: Molecules of different media
As you can see in Figure 3, particles of solids are more closely packed than particles of liquid and gas. This is why sound produced in solids is much more distinct and loud than when it is propagated or produced in liquids and gas. Between liquids and gases, on the other hand, liquid particles appear more closely spaced than gases. This means that louder sound will be produced in liquids than in gases. Spacing of particles of the medium like solid, liquid and gas is an important factor on how would is transmitted. Take a look at Figure 3, liquid particles are closer to each other than the particles in the gas. Sound waves are transmitted easier in liquids. Between liquids and solids, the particles of solids are even closer together than the liquid molecules; therefore, sound travels even faster in solids than in liquids. Since different media transmit sound differently, sound travels at different speeds in different materials. Since solid is the best transmitter of sound, sound travels fastest in solids and slowest in gases. The table below shows the speed of sound in different materials. Table 1: Speed of sound in different materials Materials
Speed of Sound V (m/s)
Air (0oC) He (0oC) H (20oC) Water Seawater Iron and Steel Aluminum Hard wood
331 1005 1300 1440 1560 5000 5100 4000
Sound speed is dependent on several factors such as (1) atmospheric pressure, (2) relative humidity, and (3) atmospheric temperature. Remember these weather elements you studied in your earlier grades? High values of these elements lead to faster moving sound. When you are in the low lands and the surrounding is hot, sound travels fast. Do you want to know why sound travels faster in hot air? There are more molecular interactions that happen in hot air. This is because the hot particles of air gain more kinetic energy and so there is also an increase in the mean velocity of the molecules. Since sound is a consequence of energy transfer through collisions, more collisions and faster collisions means faster sound. 164
Going a little deeper on this, speed of sound basically depends on the elastic property and the inertial property of the medium on which it propagates. The elastic property is concerned with the ability of the material to retain or maintain its shape and not to deform when a force is applied on it. Solids as compared to liquids and gases have the highest elastic property. Consequently, solid is the medium on which sound travels fastest. This means that the greater the elastic property, the faster the sound waves travel. The inertial property, on the other hand, is the tendency of the material to maintain its state of motion. More inertial property means the more inert (more massive or greater mass density) the individual particles of the medium, the less responsive they will be to the interactions between neighboring particles and the slower that the wave will be. Within a single phase medium, like air for example, humid air is more inert than humid air. This is because water that has changed to vapor is mixed with the air. This phenomenon increases the mass density of air and so increases the inertial property of the medium. This will eventually decrease the speed of sound on that medium. Sound cannot travel in a vacuum. Remember that sound is a mechanical wave which needs medium in order to propagate. If no matter exists, there will be no sound. In the outer space, sound would not be transmitted. Sound waves possess characteristics common to all types of waves. These are frequency, wavelength, amplitude, speed or velocity, period and phase. Just like other waves, sound also exhibits wave properties just like reflection, refraction, diffraction, and interference. More than these properties are pitch and loudness of sound. Pitch refers to the highness or lowness of sound. Loudness is how soft or how intense the sound is as perceived by the ear and interpreted by the brain. Do you want to find out more characteristics and properties of sound? Activity No. 2 will let your discover some of these properties using your sounding box.
Activity 2 Properties and characteristics of sound Objective In this activity, you will use your sounding box to describe the characteristics of sound and compare them with those of sound produced by a guitar.
Materials Needed
Sounding Box Wooden rod Ruler Guitar
165
Procedure Part 1: Sounding the Box... 6.
Label the rubber bands of your sounding box as S1, S2 and so on. Labeling should start with the thinnest rubber band.
7.
Pluck each rubber band. Listen to the sounds produced.
Q1. What did you observed when you plucked each of the rubber bands and sound is produced? How then is sound produced? Q2. Is there a difference in the sound produced by each of the rubber bands? How do they differ? Q3. Which band produced a higher sound? Which band produced a lower sound? Q4. How can you make a softer sound? How can you make a louder sound? Q5. What factors affect the pitch and loudness of the sound produced by the rubber bands? 8.
Stretch one of the rubber bands and while doing so, pluck it again.
Q6. Is there a change in the sound produced when you pluck the rubber band while stretching it? How does stretching the rubber band affect the pitch of the sound produced? 9.
Place a ruler (on its edge) across the sounding box as shown in Figure 4. Pluck each rubber band and observe.
ruler
ruler
Q7. Is there a difference in the sound produced when the ruler is placed across the box? Figure 4: With stretch rubber bands
10.
Move the ruler off center to the left or to a diagonal position so that one side of each rubber band is shorter than the other side (Figure 5). Pluck again each rubber band on each side of the ruler and observe. Figure 5: Diagonal stretching of the bands 166
Q8. Which part of the rubber band (shorter side or longer side) provides higher pitch? Which part provides lower pitch? Q9. Again, what factors affect the pitch of the sound produced by the rubber bands?
Part 2: The Guitar... 11.
Strum each guitar string without holding the frets. (String #0 is the lower most string while string #6 is the uppermost string.)
12.
Record all you observations in the table provided. String # 0 1 2 3 4 5 6
Pitch (High or Low)
Q10.
Which string vibrates fastest when strummed?
Q11.
Which string vibrates slowest when strummed?
Q12.
Which string has the highest frequency?
Q13.
Which string has the highest pitch?
Q14.
Which has the lowest frequency?
Q15.
Which string has the lowest pitch?
Q16.
How would you relate pitch and frequency?
The highness or lowness of sound is known as the pitch of a sound or a musical note. In Activity 2, you were able to relate vibrations, frequency and pitch using your improvised sounding box and a guitar. The pitch of a high frequency sound is also high and a low frequency sound is also; lower in pitch.
167
When you were in your earlier grades you studied about the human ear. Our ear and that of animals are the very sensitive sound detectors. The ear is a part of the peripheral auditory system. It is divided into three major parts: the outer ear, the middle ear and the inner ear. The outer ear called the pinna collects the sound waves and focuses them into the ear canal. This canal transmits the sound waves to the eardrum. Figure 6 The human ear The ear canal is the eardrum membrane or the tympanum. It separates the outer and the middle ears physically. Air vibrations set the eardrum membrane in motion that causes the three smallest bones (hammer, anvil and stirrup) to move. These three bones convert the small-amplitude vibration of the eardrum into largeamplitude oscillations. These oscillations are transferred to the inner ear through the oval window. Behind the oval window is a snail-shell shaped liquid –filled organ called the cochlea. The large-amplitude oscillations create waves that travel in liquid. These sounds are converted into electrical impulses, which are sent to the brain by the auditory nerve. The brain, interprets these signals as words, music or noise. Did you know that we can only sense within the frequency range of about 20 Hz to about 20000 Hz? Vibrational frequencies beyond 20 000 Hz is called ultrasonic frequencies while extremely low frequencies are known as infrasonic frequencies. Our ear cannot detect ultrasonic or infrasonic waves. But some animals like dogs can hear sounds as high as 50 000 Hz while bats can detect sounds as high as 100 000 Hz. We can see images of your baby brother or sister when the OB-Gyne asks your mommy or nanay to undergo ultrasound. Ultrasonic waves are used to help physicians see our internal organs. Nowadays, ultrasonic technology is of three kinds: 2-dimensional, 3-dimensional, and 4-dimensional categories. In the 3- and 4dimensional ultrasonic technologies, the features of the fetus are very clearly captured.
168
It has also been found that ultrasonic waves can be used as rodent and insect exterminators. The very loud ultrasonic sources in a building will usually drive the rodents away or disorient cockroaches causing them to die from the induced erratic behavior. What other applications of sound do you have in mind? Do you want to share them too?
Loudness and Intensity Do you still remember intensity of light in the previous module? In sound, intensity refers to the amount of energy a sound wave. Figure 7 shows varying intensity of sound. High amplitude sounds usually carry large energy and have higher intensity while low amplitude sound carry lesser amount of energy and have lower intensity.
Figure 7: Varying sounds
Sound intensity is measured by various instruments like the oscilloscope. Loudness is a psychological sensation that differs for different people. Loudness is subjective but is still related to the intensity of sound. In fact, despite the subjective variations, loudness varies nearly logarithmically with intensity. A logarithmic scale is used to describe sound intensity, which roughly corresponds to loudness. The unit of intensity level for sound is the decibel (dB), which was named after Alexander Graham Bell who invented the telephone. On the decibel scale, an increase of 1 dB means that sound intensity is increased by a factor of 10. Father and son duo interprets the loudness of a sound differently. The son considers the rock music a soft music while the father considers it a loud sound. The father may even interpret the sound as a distorted sound, which is known as noise. Noise is wave that is not pleasing to the senses.
169
Table 2. Sound Levels of different sound sources Source of sound Jet engine, 30 m away Threshold of pain Amplified rock music Old subway train Average factory Busy street traffic Normal conversation Library Close whisper Normal breathing Threshold of hearing
Level (dB) 140 120 115 100 90 70 60 40 20 10 0
Let’s see how you interpret sound yourselves. Look for 3 more classmates and try Activity 3. This will test your ability to design and at the same time show your talents!
Activity 3 Big time gig! Objectives In this activity, you should be able to: 1. create musical instruments using indigenous products and 2. use these instruments to compose tunes and present in a Gig. Students may also utilize other indigenous musical instruments.
Materials Needed
Indigenous materials such as sticks, bottles or glassware available in your locality to be used as musical instrument Localized or improvised stringed instruments Localized or improvised drum set
Procedure 1.
2. 3. 4.
Form a group of four (4). One can play a stringed instrument, while the other can play the drum and the 3rd member can use the other instrument that your group will design or create. The last member will be your group’s solo performer. Look for local materials which you can use to create different musical instruments. Try to come up with your own composition using the instruments you have created. In the class GIG you are to play and sing at least 2 songs (any song of your choice and your original composition).
170
5.
Check the Rubric included to become familiar with the criteria for which you will be rated.
Big Time Gig! Rubric Scoring Task/ Criteria Improvised/ Localized musical instruments
Composition
Performance
Cooperation and Team Work
4
3
2
1
Makes use of local or indigenous materials The improvised instruments produce good quality sound comparable to standard musical instruments.
Makes use of local materials only. The improvised instruments produce good quality sound.
Makes use of local materials only. The improvised instruments produce fair quality sound.
Makes use of local materials only. The sound produced by the improvised instruments is not clear and distinct.
The group’s original composition has good melody.
The group’s original composition has fair melody and the lyrics provided are thematic and meaningful
The group’s original composition has fair melody and the lyrics provided are NOT thematic but meaningful
The group’s original composition has fair melody and the lyrics provided are NEITHER thematic nor meaningful
The group was able to successfully use the improvised musical instruments in their GIG. The group was able to provide fair rendition.
The group was able to use the improvised musical instruments but some were out of tune The group was able to provide fair rendition.
The group was able to use the improvised musical instruments but MOST were out of tune The group was able to provide fair rendition
3 out of 4 members completed their task so as to come up with the expected output - GIG
2 out of 4 completed their task so as to come up with the expected output - GIG
Only 1 out of the 4 members did his/her job
The lyrics provided are thematic and meaningful The group was able to successfully use the improvised musical instruments in their GIG. The group was able to provide good quality rendition or performance Each one of them completed their task so as to come up with the expected output - GIG
TOTAL:
171
Score
How was your GIG? Did you enjoy this activity? Aside from the concepts and principles in sound you learned and applied for a perfect performance what other insights can you identify? Can you extend your designs to come up with quality instruments using indigenous materials? You can be famous with your artworks... Sound waves are mechanical waves than need for a medium for sound to propagate. Vibrations of the medium create a series of compression and rarefaction which results to longitudinal waves. Sound can travel in all media but not in vacuum. Sound is fastest in matter that is closely packed like solid and slowest in gas. Speed of sound is dependent on factors like temperature, humidity and air pressure. High temperature brings much faster sound. Increased humidity, on the other hand makes sound travel slower. As pressure is increased, speed is also increased. Inertial and elastic properties of the medium also play an important part in the speed of sound. Solids tend to be highly elastic than gases and thus sound travel fastest in solids. In a single phase matter however, the inertial property which is the tendency of the material to maintain its motion also affect speed of sound. Humid air is more massive and is more inert than dry air. This condition brings lesser molecular interactions and eventually slower sound. Sound, just like other waves do have characteristics such as speed, frequency, wavelength, amplitude, phase and period. Like any other wave, sound exhibit properties like reflection, refraction, interference and diffraction. Other properties are loudness and pitch. Pitch is dependent on the frequency of sound wave. The higher frequency the higher the pitch of the sound produced. Organisms like us are capable of sensing sound through our ears. Just like other organism, our ears do have parts that perform special tasks until the auditory signals reach and are interpreted by our brain. Frequencies beyond the audible to human are known as ultrasonic (beyond the upper limit) and infrasonic (below the lower limit). Intensity and loudness are quantitative and qualitative descriptions of the energy carried by the wave. High amplitude waves are intense and are sensed as loud sound. Low amplitude sound waves are soft sound. Music is a special sound that forms patterns and are appealing to our sense of hearing.
Up Next. Light In the next module, you would learn about visible light, the most familiar form of electromagnetic waves, since it is the part of the electromagnetic spectrum that the human eye can detect. Through some interesting activities, you would come across the characteristics of light, how it is produced and how it propagates. You would need the concepts that you learned from this module to fully understand and appreciate the occurrence of light.
Reading Materials/Links/Websites http://www.physicsclassroom.com/Class/sound/u11l2c.cfm http://en.wikipedia.org/wiki/Sound#Sound_wave_properties_and_characteristics http://personal.cityu.edu.hk/~bsapplec/characte.htm http://www.slideshare.net/agatonlydelle/physics-sounds
172
Suggested time allotment: 5 to 6 hours
Unit 3 MODULE
4
LIGHT
Do you still remember Sir Isaac Newton? What about Christian Huygens? Did you meet them in your earlier grades? These people were the first to study about light. In this module, you will learn about light. You will also find out that there are different sources of light and that light exhibits different characteristics and properties. Finally, you will design a simple activity to test whether light travels in a straight light or not.
What are the common sources of light? How do these common sources produce light? What are the common properties and characteristics of light?
Sir Isaac Newton believed that light behaves like a particle while Christian Huygens believed that light behaves like a wave. A 3rd scientist, Max Planck came up with what is now known as the Dual-Nature of Light. He explained that light can be a particle and can also be a wave. To complete our knowledge about the nature of light, James Clark Maxwell proposed the Electromagnetic Theory of Light. While these scientists dig deep into the nature of light and how light are propagated, let us be more familiar with ordinary materials we use as common sources of light. The Sun for example is known as a natural source of light. Sun is also considered as a luminous body (an object capable of producing its own light). Other sources are the lamps, bulbs, and candles. These are the artificial sources. In your earlier grades you learned about energy transformation. Energy transformation is needed to convert or transform forms of energy to light or other forms. In bulbs, electric potential is converted to light. In lamps, chemical energy is transformed to light.
173
In Activity 1, you will try to observe transformation of chemical energy from chemical substances such as oil to light. Further, you will also gather data which chemical substance is best by relating it to the brightness of the light produced. In this activity, you will use the langis kandila or lampara as we call it in the Philippines or the Diwali lights as it is known in other countries like India.
Activity 1 Light sources: Langis kandila or lampara Objectives In this activity, you should be able to:
1. construct a simple photometer; 2. determine which chemical substance produce the brightest light; and 3. infer that brightness of light is dependent on the distance of the source. Materials Needed
an electric glow lamp (Small lamp is needed) candle - weighing 75 grams wedge with sloping surfaces (sharp angle about 60° to 70° that serve as the photometer (made of white wood or paper) langis kandila or lampara variety of vegetable oil (about 5) aluminum pie containers or small clay pots cotton string for wick set of books or tripod that will serve as platform for Diwali lights
Procedure Part 1: Improvised Photometer Arrange the electric glow lamp, the candle and the wedge as shown on the right. Make sure that you do this activity in a dark room for good results. 1
2 Figure 1. Improvised photometer set up
Illuminate the side “A” of the wedge by the lamp and side “B” by the candle. In general the lamp side will look brighter than the other. 174
Move the wedge nearer to the candle to a spot at which you as an observer, looking down on the two surfaces of the wedge (from “C”) cannot see any difference between them in respect of brightness. (They are then equally illuminated; that is to say the candle light falling on “B” is equal in intensity to the electric light falling on “A.”) Calculate the power of the lamp relative to the candle. (e.g. If both side of the wedge showed equal illumination when it is about 200 cm from 1, and 50 cm from 2, the distances are as 4 to 1. But as light falls off according to the square of the distance: (200)2 = 40 000 and (50)2 = 2 500 or 16 to 1.). Thus the candle-power of the lamp is 16. Q1. What is the candle power of your set up? (Include your computations.) Part 2: Langis Kandila or Lampara 1.
Make 5 langis kandila or lampara using aluminium pie containers or small clay pots as shown. Label your langis kandila as DLKL1, DL-KL2 and so on.
2.
Pour different variety of vegetable oil in each of the pot.
3.
Use the improvised photometer to determine the brightness of each of the candle.
4.
Replace the candle you used in the 1st part with the langis kandila.
5.
Compute the candle power of the lamp with respect to the langis kandila. You may refer to step 4 for the step by step process of determining the candle power using the improvised photometer. Record your data on the provided table:
Figure 2. Langis kandila or lampara
Table 1. Brightness of Vegetable Oil Variety Diwali Lights/Langis Vegetable Oil Variety Kandila DL-LK 1 Canola Oil DL-LK 2 Butter DL-LK 3 Margarine DL-LK 4 Corn Oil DL-LK 5 Olive Oil
Brightness/Luminous Intensity (Candela)
Q2. Which among the langis kandila or lampara is the brightest?
175
Part 3: Intensity vs Distance from light source 1.
Position your brightest Diwali light or langis kandila 20 inches or about 50 cm from the wedge. Compute the brightness of the Diwali light.
2.
Move the langis kandila or Diwali light 10 cm closer then compute the brightness.
3.
Repeat step 2 and each time move the langis kandila or Diwali light 10 cm closer to the wedge. Compute the corresponding brightness and record your data on the table below. Distance from the Wedge (cm) 50 40 30 20 10
Observation
Brightness (Candela)
Q3. How would you relate the brightness or intensity of light with the distance from the source? Brightness of light depends on the source and the distance from the source. Brightness however, is qualitative and is dependent of the person’s perception. Quantitatively, brightness can be expressed as luminous intensity with a unit known as candela. The unit expression came from the fact that one candle can approximately represent the amount of visible radiation emitted by a candle flame. However, this decades-ago assumption is inaccurate. But we still used this concept in Activity 1 as we are limited to an improvised photometer. If you are using a real photometer on the other hand, luminous intensity refers to the amount of light power emanating from a point source within a solid angle of one steradian. Further, in Activity 1, varied chemical sources produced different light intensity. Likewise, different distances from the light source provided varied intensity. As mentioned earlier, James Clark Maxwell discovered the Electromagnetic Theory of Light. He combined the concepts of light, electricity and magnetism to come up with his theory forming electromagnetic waves. Since these are waves they also exhibit different characteristics of waves such as wavelength, frequency and wave speed which you have studied in the previous module. There are different forms of electromagnetic waves arranged according to frequency. This arrangement of the electromagnetic waves is known as Electromagnetic spectrum. The visible part of which is known as white light or visible light. The next activity will lead you to explore the characteristics of the electromagnetic spectrum.
176
Activity 2 My spectrum wheel Objectives In this activity, you should be able to 1. construct a spectrum wheel and 2. explore the characteristics of light such as energy, frequency and wavelength.
Materials Needed
Spectrum Wheel Pattern Cardboard or illustration board Button fastener Glue or paste
TAKE CARE!
Handle all sharp Objects with care.
Procedure Part 1: Spectrum Wheel 1.
Cut the two art files that make up the wheel on the next pages.
2.
Cut along the lines drawn on the top wheel. The small window near the center of the wheel should be completely cut out and removed.
3.
Punch a whole into the center of the two wheels together. You may use a button fastener to hold the two wheels securely in place, one on top of the other, but they should be free to rotate relative to each other.
4.
When you see a region of the EM spectrum show up in the open window and the "W,F,E" that correspond to that region showing up under the flaps then you know that you have done it right.
177
5.
Source: Sonoma State University (http://www.swift.sonoma.eu)
178
179
Part 2: Characteristics of Light Try out your Spectrum Wheel by positioning the inner most of the flaps on EM SPECTRUM. This will simultaneously position the other flaps to ENERGY, WAVELENGTH & FREQUENCY. Turn the upper wheel and observe the combinations. Fill in the table below with the corresponding combinations you have observed using your Spectrum Wheel. Table 2. Characteristics of Light EM Energy Spectrum Radio
Frequency
Wavelength
Frequency x wavelength
Microwave Infrared Visible Light Ultraviolet X-Ray Gamma Ray
Q1. How are frequency and wavelength related for a specific region of the spectrum? Q2. What can you observe with the values of the product of frequency and wavelength in the different spectra? Q3. How is ENERGY related to FREQUENCY?
Now that we are familiar with the electromagnetic spectrum and the corresponding energies, frequencies and wavelength probably we can see some applications of these in everyday living. UV rays are highly energetic than other spectral regions on its left. This could be a possible reason why we are not advised to stay under the sun after 9:00 in the morning. Prolong use of mobile phones may cause ear infection. This may be due to a higher energy emitted by microwaves used in cellular phones than radio waves commonly used in other communication devices. What about the visible spectrum? Do you want to know more about this spectral region?
180
What are the frequencies and energies of the visible spectrum? This is the visible light. Sir Isaac Newton used a prism to show that light which we ordinarily see as white consists of different colors. Dispersion is a phenomenon in which a prism separates white light into its component colors. Activity 3 will provide you more information about visible light. In this activity, you will be able to detect relationships between colors, energy, frequency, wavelength and intensity. Figure 3. Color spectrum
Activity 3 Colors of light – color of life! Objectives In this activity, you should be able to 1. make a color spectrum wheel; 2. explore the characteristics of color lights; and 3. observe how primary colors combine to form other colors.
Materials Needed
Color Spectrum Wheel Pattern Cardboard or illustration board white screen plastic filters (green, blue and red) 3 pieces of high intensity flashlights Handle all sharp TAKE button fastener Objects with CARE! glue or paste care.
Procedure Part 1: Color Wheel 1. 2.
3.
4.
Cut the two art files that make up the wheel on the next pages. Cut along the lines drawn on the top wheel. Cut the 2 sides as shown. The small window near the center of the wheel should be completely cut out and removed. Punch a hole at the center of the two wheels. You may use a button fastener to secure the two wheels together one on top of the other, but they should be free to rotate relative to each other. When you see a region of the Color spectrum show up in the open window and the "W,F,E" that correspond to that region showing up under the flaps then you know that you have done it right. 181
182
183
Part 2: Characteristics of Light 1.
2. 3.
Try out your Color Spectrum Wheel by positioning the inner most of the flaps on COLOR SPECTRUM. This will simultaneously position the other flaps to ENERGY, WAVELENGTH & FREQUENCY. Turn the upper wheel and observe the combinations. Fill in the table below with the corresponding combinations you have observed using your Spectrum Wheel. Table 1. Characteristics of Color Lights Color Spectrum
Energy (eV)
Frequency (THz)
Wavelength (nm)
Frequency x wavelength (m/s)
Red Orange Yellow Green Blue Violet 4.
You will need to convert the equivalents of frequencies to Hz and the equivalent wavelengths to meters. Note that terra (T) is a prefix for 1014 while nano (n) is a prefix equivalent to 10-9.
Q1. Which color registers the highest frequency? shortest wavelength? Q2. Which color registers the lowest frequency? longest wavelength? Q3. What do you observe with the wavelength and frequency of the different colors? Q4. What did you observe with the product of wavelength and frequency for each color? What is the significance of this value? Q5. What can you say about the speed of the different colors of light in air? Q6. Give a plausible explanation as to why white light separate into different colors. Part 3: Combining Colors 1.
2.
3.
Cover the lens of the flashlight with blue plastic filter. Do the same with the 2 other flashlights. The 2nd flashlight with green plastic filter and the 3rd with red plastic filter. Ask 2 other groupmates to hold the 2 other flashlight while you hold on to the 3rd one. Shine these flashlights on the white screen and note the colors projected on the screen. Let 2 color lights from the flashlights overlap. Observe what color is produced and fill in the table below. Table 2. Color that you see Color of Plastic Filter Green Blue Red
Color that you see projected on the screen
184
Table 3. Color Mixing Color Combination Green + Blue Blue + Red Red + Green Red + Green + Blue
Resulting Color
Dispersion, a special kind of refraction, provided us color lights. This phenomenon is observed when white light passes through a triangular prism. When white light enters a prism and travels slower in speed than in vacuum, color separation is observed due to variation in the frequencies (and wavelength) of color lights. Remember the concept of refractive indices in the previous module? The variations in frequencies (and wavelengths) are caused by the different refractive indices of the varying color light. Thus, blue light with greater refractive index refracts more and appears to bend more than red light. But do you really think that light will bend when travelling in space? The last activity in this module will test your ability to design an experiment to test if light travels in a straight line or not.
Activity 4 Light up straight! Objective In this activity, you should be able to design an experiment given several materials to show that light travels in a straight line.
Materials Needed
2 pieces of cardboard cutting tool bright room ruler or meter stick permanent marker pencil any object (e.g. medium size Johnson’s face powder box)
TAKE CARE!
Handle all sharp objects with care. Handle all lighting tools with care to avoid being burnt.
General Instructions 1. 2.
Given the materials design a 5-6 step procedure to test that light follows a straight line or not. Remember that you are only allowed to use the materials specified in this particular activity. 185
3.
Check the rubric scoring for your guide. Light Up Straight! Rubric Scoring Task/ Criteria
Experiment Procedure
Result of Experiment Try-out/ Feasibility
Cooperation and Team Work
4
Steps are logically presented. The procedure included about 5-6 steps. All materials given to the group are utilized in the procedure The group has successfully attained the object to prove that light travels in a straight line using their designed procedure. Each one of them completed their task so as to come up with the expected output.
3
2
Steps are Steps are logically logically presented. presented. The procedure The procedure included about included about 3-4 steps. 3-4 steps. 75% of the 50% of the materials given materials given to the group to the group are utilized in are utilized in the procedure the procedure The group has The group has attained the object partially attained to prove that light the object to prove travels in a straight that light travels in line using their a straight line designed using their procedure but designed there are some procedure. steps that are not very clear. About 75% of the About 50% of the members members completed their completed their task so as to task so as to come up with the come up with the expected output. expected output.
1
Score
Steps are logically presented. The procedure included about 2-3 steps. 25% of the materials given to the group are utilized in the procedure The group had some effort but was not able to attained the object to prove that light travels in a straight line using their designed. About 25% of the members did his/her job
TOTAL:
Light, accordingly has wavelike nature and particle-like nature. As a wave, it is part of the electromagnetic waves as the visible spectrum. This visible spectrum is also known as white light. White light undergoes dispersion when it passes through a prism. The variations of refractive indices result to variations in the refraction of color lights dependent on the frequencies (and wavelength) of the color lights. This brings about blue light being refracted more than the other color lights and thus appears to be bent. However, light travels in a straight line path in a particular medium. Brightness or intensity and colors are special properties of light. These can be observed in different phenomena such as rainbows, red sunset, and blue sky. You can identify many other applications of light and colors as you become keen observers of natural phenomena.
Reading Materials/Links/Websites http://amazing-space.stsci.edu/resources/explorations/groundup/ lesson/glossary/term-full.php?t=dispersion http://www.physicsclassroom.com/class/refrn/u14l4a.cfm 186
Suggested time allotment: 5 to 6 hours
Unit 3 MODULE
5
HEAT
For sure, you have used the word ‘heat’ many times in your life. You have experienced it; you have observed its effects. But have you ever wondered what heat really is? In your earlier grades, you learned that heat moves from the source to other objects or places. Example is the kettle with water placed on top of burning stove. The water gets hot because heat from the burning stove is transferred to it. This module aims to reinforce your understanding of heat as an energy that transfers from one object or place to another. You will determine the conditions necessary for heat to transfer and the direction by which heat transfers by examining the changes in the temperature of the objects involved. You will observe the different methods of heat transfer and investigate some factors that affect these methods. The results will help you explain why objects get hot or cold and why some objects are seemingly colder or warmer than the others even if they are exposed to the same temperature.
How is heat transferred between objects or places? Do all objects equally conduct, absorb, or emit heat?
What is Heat? Have you ever heard of the term “thermal energy” before? Any object is said to possess thermal energy due to the movement of its particles. How is heat related to thermal energy? Like any other forms of energy, thermal energy can be transformed into other forms or transferred to other objects or places. Heat is a form of energy that refers to the thermal energy that is ‘in transit’ or in the process of being transferred. It stops to become heat when the transfer stops. After the energy is transferred, say to another object, it may again become thermal energy or may be transformed to other forms.
187
Thermometer Heat transfer is related to change in temperature or change in the relative hotness or coldness of an object. Most of the activities found in this module will ask you to collect and Figure 1. Thermometer analyze temperature readings to arrive at the desired concepts. To achieve this, you have to use the laboratory thermometer, which is different from the clinical thermometer we use to determine our body temperature. The kind that you most probably have in your school is the glass tube with fluid inside, usually mercury or alcohol. Always handle the thermometer with care to avoid breaking the glass. Also, be sure that you know how to read and use the device properly to get good and accurate results. Inform your teacher if you are not sure of this so that you will be guided accordingly.
Activity 1 Warm me up, cool me down Objective In this activity, you should be able to describe the condition necessary for heat transfer to take place and trace the direction in which heat is transferred.
Materials Needed
2 small containers (drinking cups or glasses) 2 big containers (enough to accommodate the small containers) tap water hot water food coloring laboratory thermometers (with reading up to 100oC)
Procedure 1.
Label the small and big containers as shown in Figure 2.
2.
Half fill containers 1, 2, and A with tap water. Half fill also container B with hot water. Be careful when you pour hot water into the container.
3.
Add few drops of food coloring on the larger containers. 188
Figure 2
4.
Measure the initial temperature of water in each of the 4 containers, in degree Celsius (°C). Record your measurements in Table 1.
5.
Carefully place container 1 inside container A (Figure 3). This will be your Setup 1.
6.
Place also container 2 inside container B. This will be your Setup 2.
7.
Measure the temperature of water in all containers 2 minutes after arranging the setups. Record again your measurements in the table (after 2 minutes).
8.
Continue to measure and record the temperature of water after 4, 6, 8, and 10 minutes. Write all your measurements in the table below.
Setup 2
Setup 1
Figure 3
Table 1. Temperature readings for Setup 1 and Setup 2 Temperature (°C) of Water After Container
Setup 1
Setup 2
0 min (initial)
2 mins
4 mins
6 mins
8 mins
10 mins
1-Tap water A-Tap water 2-Tap water B-Hot water
Q1. In which setup did you find changes in the temperature of water inside the containers? In which setup did you NOT find changes in the temperature of water inside the containers? Q2. In which setup is heat transfer taking place between the containers? Q3. What then is the condition necessary for heat transfer to take place between objects? 9.
Refer to the changes in the temperature of water in the setup where heat transfer is taking place. Q4. Which container contains water with higher initial temperature? What happens to its temperature after 2 minutes? Q5. Which container contains water with lower initial temperature? What happens to its temperature after 2 minutes? Q6. If heat is related to temperature, what then is the direction of heat that transfers between the containers? 189
Q7. What happens to the temperature of water in each container after 4, 6, 8, and 10 minutes? What does this tell us about the heat transfer taking place between the containers? Q8. Until when do you think will heat transfer continue to take place between the containers?
Temperature (°C)
If your teacher allows it, you may continue to measure the temperature of the water in both containers for your basis in answering Q8. And if you plot the temperature vs. time graph of the water in both containers, you will obtain a graph similar to Figure 4.
Time (s) Figure 4 10. Q9. Q10. Q11.
Analyze the graph and answer the following questions: What does the blue curved line on the graph show? Which container does this represent? What does the red curved line on the graph show? Which container does this represent? What does the orange broken line in the graph show? Is heat transfer still taking place during this time? If yes, where is heat transfer now taking place?
If you do not have laboratory thermometers in your school, you may still perform the activity above using your sense of touch. You can use your fingers or hands to feel the objects being observed. But be very careful with this especially if you are dealing with hot water. You have to take note also that touching is not always reliable. Try out this simple activity below. Prepare three containers. Half fill one container with hot water, but not hot enough to burn your hand. Pour very cold water into the second container and lukewarm water in the third container. First, simultaneously place your left hand in the hot water and your right hand in the cold water. Keep them in for a few minutes. Then take them out, and place both of them together into the container with lukewarm water. How do your hands feel? Do they feel equally cold? 190
If you try out this activity, you will observe that your left hand feels the water cold while your right hand feels it warm. This is due to the initial conditions of the hands before they were placed into the container with lukewarm water. So if you use sensation to determine the relative hotness or coldness of the objects, make sure to feel the objects with different hands or fingers.
How Does Heat Transfer? In the previous activity, you explored the idea that heat transfers under certain conditions. But how exactly is heat transferred? The next activities will allow you to explore these different methods by which heat can be transferred from one object or place to another.
Activity 2 Which feels colder? Objective In this activity, you should be able to describe heat transfer by conduction and compare the heat conductivities of materials based on their relative coldness.
Materials Needed
small pieces of different objects (copper/silver coin, paper, aluminum foil, iron nail, etc.) laboratory thermometer
Procedure Part A: To be performed one day ahead. 1.
Place a laboratory thermometer inside the freezer of the refrigerator.
2.
Place also your sample objects inside the freezer at the same time. Leave them inside the freezer overnight.
Part B: To be performed the next day. 3. Take the temperature reading from the thermometer inside the freezer. Q1. What is the temperature reading inside the freezer? Q2. If ever there is a way to measure also the temperature of the objects placed inside the freezer, how do you think will their temperature compare with each other and with the temperature reading from the thermometer?
191
4. Touch one object lightly with your finger and feel it. Q3. Did heat transfer take place between your finger and the object? If yes, how and in what direction did heat transfer between them? Q4. Did you feel the object cold? What made it so? (Relate this to your answer in Q3.) 5.
Touch the rest of the objects inside the freezer using different fingers, then observe. Q5. Did the objects feel equally cold? What does this tell us about the amount of heat transferred when you touch each object? Q6. Which among the objects feels ‘coldest’? Which feels ‘warmest’? Q7. Which among the objects is the best conductor of heat? Which object is the poorest conductor of heat? Activity 2 demonstrates heat transfer by conduction, one of the methods by which heat is transferred. Conduction takes place between objects that are in contact with each other. The energy from the object of higher temperature is transferred to the other object through their particles that are close or in contact with each other. Then the particles receiving the energy will also transfer the energy to other places within the object through their neighboring particles. During this process, only the energy moves, not the matter itself. This can be observed in Activity 1. You have observed that the hot colored water stayed inside container B and did not mix with the water inside container 2. So this shows that only the energy transferred between the containers. Here is another example of heat transfer by conduction. Think of a metal spoon put in a bowl of a hot champorado that you were about to eat when you suddenly remembered that you had to do first a very important task. When you came back, you noticed that the handle of the spoon became really hot! How do you think this happened? The heat from the champorado is transferred to the part of the spoon that is in direct contact with the food by conduction. Then it is transferred to the cooler regions of the spoon through its particles. Why did you feel the spoon hot? When you touched the spoon, heat is also transferred to your hand by conduction. So your hand gained heat or thermal energy, and this makes you feel the object hot. Can you now explain why your hand that was previously dipped into hot water felt the lukewarm water cold while the other hand that was previously dipped into very cold water felt it hot?
Heat Conductivities In the previous activity, you found out that some objects conduct heat faster than the others. This explains why we feel some objects colder or warmer than the others even if they are of the same temperature. Which usually feels warmer to our feet – the tiled floor or the rug? More accurate and thorough experiments had been carried out long before to determine the heat or thermal conductivity of every material. The approximate values of thermal conductivity for some common materials are shown below: 192
Table 2: List of thermal conductivities of common materials Conductivity Material Material W/(m·K) Silver 429 Concrete Copper 401 Water at 20°C Gold 318 Rubber Aluminum 237 Polypropylene plastic Ice 2 Wood Glass, ordinary 1.7 Air at 0°C
Conductivity W/(m·K) 1.1 0.6 0.16 0.25 0.04 - 0.4 0.025
Solids that conduct heat better are considered good conductors of heat while those which conduct heat poorly are generally called insulators. Metals are mostly good conductors of heat. When we use a pot or pan to cook our food over a stove, we usually use a pot holder made of fabrics to grasp the metal handle. In the process, we are using an insulator to prevent our hand from being burned by the conductor, which is the metal pan or pot. Why are woven fabrics that are full of trapped air considered good insulators?
Activity 3 Move me up You have previously learned that water is a poor conductor of heat, as shown in Table 2. But why is it that when you heat the bottom of the pan containing water, the entire water evenly gets hot quickly? Think of the answer to this question while performing this next activity.
Objective In this activity, you should be able to observe and describe convection of heat through liquids.
Materials Needed
2 transparent containers (drinking glass, beaker, bottle) dropper hot water cold water piece of cardboard
Be careful not to bump the table or shake the container at any time during the experiment.
Procedure 1.
Fill one of the glass containers with tap water. 193
2.
While waiting for the water to become still, mix in a separate container a few drops of food coloring with a small amount of very cold water. (You may also make the food coloring cold by placing the bottle inside the refrigerator for at least an hour before you perform the activity.)
3.
Suck a few drops of cold food coloring using the dropper and slowly dip the end of the medicine dropper into the container with tap water, down to the bottom. See to it that the colored water does not come out of the dropper yet until its end reaches the bottom of the container.
4.
Slowly press the dropper to release a small amount of the liquid at the bottom of the container. Then slowly remove the dropper from the container, making sure not to disturb the water. Observe for few minutes. Q1. Does the food coloring stay at the bottom of the container or does it mix with the liquid above it? 5.
Fill the other container with hot water.
6.
Place the cardboard over the top of the container with hot water. Then carefully place the container with tap water on top of it. The cardboard must support the container on top as shown in Figure 5. What happens to the food coloring after placing the container above the other container? Why does this happen? How is heat transfer taking place in the setup? Where is heat coming from and where is it going? Is there a transfer of matter, the food coloring, involved Figure 5 during the transfer of heat? You have just observed another method of heat transfer, called convection. In your own words, how does convection take place? How is this process different from conduction? Do you think convection only occurs when the source of heat is at the bottom of the container? What if the source of heat is near the top of the container? You may try it by interchanging the containers in your previous experiment.
Q2.
Q3. Q4. Q5.
Q6.
What you found out in this experiment is generally true with fluids, which include liquids and gases. In the next quarter, you will learn about convection of heat in air when you study about winds. So what happens in your experiment? When you placed the glass on top of another glass with hot water, heat transfer takes place from the hot water to the tap water including the colored water. This makes these liquids expand and become lighter and float atop the cooler water at the top of the container. This will then be replaced by the cooler water descending from above.
194
Activity 4 Keep it cold So far you have learned that heat can be transferred by conduction and convection. In each method, a material, either a solid or a liquid or gas, is required. But can heat also transfer even without the material? If we stay under the sun for a while, do we not feel warm? But how does the heat from this very distant object reach the surface of the earth? The transfer of energy from the sun across nearly empty space is made possible by radiation. Radiation takes place even in the absence of material. Do you know that all objects, even ordinary ones, give off heat into the surrounding by radiation? Yes, and that includes us! But why don't we feel it? We do not feel this radiation because we are normally surrounded by other objects of the same temperature. We can only feel it if we happen to stand between objects that have different temperature, for example, if we stand near a lighted bulb, a burning object, or stay under the Sun. All objects emit and absorb radiation although some objects are better at emitting or absorbing radiation than others. Try out this next activity for you to find out. In this activity, you will determine how different surfaces of the object affect its ability to absorb heat.
Introduction One hot sunny day, Cobi and Mumble walked into a tea shop and each asked for an order of iced milk tea for takeout. The crew told them as part of their promo, their customers can choose the color of the tumbler they want to use, pointing to the array of containers made of the same material but are of different colors and textures. Cobi favored the container with a dull black surface, saying that the milk tea will stay cooler if it is placed in a black container. Mumble remarked that the tea would stay even cooler if it is in a container with bright shiny surface.
Prediction 1. 2.
If you were in their situation, which container do you think will keep the iced milk tea cooler longer? Explain your choice. Assuming an initial temperature of 5°C, predict the possible temperatures of the milk tea in each container after 5, 10, 15, and 20 minutes. Assume that the containers are covered. Cup
Dull black container Bright shiny container
0 min
Temperature (°C) 5 min 10 min 15 min
5°C 5°C 195
20 min
Task: Design a laboratory activity that will enable you to test your prediction. See to it that you will conduct a fair investigation. Start by answering the questions below:
What problem are you going to solve? (Testable Question)
What are you going to vary? (Independent variable)
What are you not going to vary? (Controlled Variables)
What are you going to measure? (Dependent variables)
1.
Write down your step by step procedure. Note that you may use the light from the sun or from the lighted bulb as your source of energy.
2.
Collect your data according to your procedure. Present your data in tabulated form.
3.
Analyze your data and answer the following questions:
Q1. Q2. Q3. Q4.
Which container warmed up faster? Which container absorbs heat faster? Which container will keep the milk tea cooler longer? Is your prediction correct? Will the same container also keep a hot coffee warmer longer that the other?
Activity 5 All at once So far, you have learned that heat can be transferred in various ways. You have also learned that different objects absorb, reflect, and transmit heat differently. In the next activities, you will not perform laboratory experiments anymore. All you have to do is to use your understanding so far of the basic concepts of heat transfer to accomplish the given tasks or answer the questions being asked.
Task 1 Heat transfer is evident everywhere around us. Look at the illustration below. This illustration depicts several situations that involve heat transfer. Your task is to identify examples of situations found in the illustration that involve the different methods of heat transfer.
196
Figure 6 1.
Encircle three situations in the drawing that involve any method of heat transfer. Label them 1, 2, and 3.
2.
Note that in your chosen situations, there could be more than one heat transfer taking place at the same time. Make your choices more specific by filling up Table 3.
Table 3: Examples of heat transfer Description
Which object gives off heat?
1
2
3
197
Which object receives heat?
What is the method of heat transfer?
Task 2 Below is a diagram showing the basic parts of the thermos bottle. Examine the parts and the different materials used. Explain how these help to keep the liquid inside either hot or cold for a longer period of time. Explain also how the methods of heat transfer are affected by each material.
Stopper made of plastic or cork Silvered inner and outer glass wall
Hot liquid
Vacuum between inner and outer wall Outer casing made of plastic or metal
Ceramic base
Figure 7: Basic parts of a thermos bottle
In the next module, you will learn about another form of energy which you also encounter in everyday life, electricity. Specifically, you will learn about the different types of charges and perform activities that will demonstrate how objects can be charged in different ways. You will also build simple electric circuits and discuss how energy is transferred and transformed in the circuit.
Links and References Sootin, H. (1964). Experiments with heat. W.W. Norton and Company, Inc. Where is Heat coming from and where is it going? Retrieved March 10, 2012 from http://www.powersleuth.org/docs/EHM%20Lesson%204%20FT.pdf Conduction, Convection, Radiation: Investigating Heat Transfers. Retrieved March 10, 2012 from http://www.powersleuth.org/docs/EHM%20Lesson%205%20FT.pdf
198
Suggested time allotment: 5 to 6 hours
Unit 3 MODULE
6
ELECTRICITY
In Module 5, you learned about heat as a form of energy that can be transferred through conduction, convection and radiation. You identified the conditions that are necessary for these processes to occur and performed activities that allowed you to investigate the different modes of heat transfer. Finally, you learned to distinguish between insulators and conductors of heat and were able to identify the uses of each. Now you will learn about another form of energy which you encounter in everyday life, electricity. You must be familiar with this energy since it is the energy required to operate appliances, gadgets, and machines, to name a few. Aside from these manmade devices, the ever-present nature of electricity is demonstrated by lightning and the motion of living organisms which is made possible by electrical signals sent between cells. However, in spite of the familiar existence of electricity, many people do not know that it actually originates from the motion of charges. In this module, you will learn about the different types of charges and perform activities that will demonstrate how objects can be charged in different ways. You will also learn the importance of grounding and the use of lightning rods. At the end of the module you will do an activity that will introduce you to simple electric circuits. The key questions that will be answered in this module are the following:
What are the different types of charges? How can objects be charged? What is the purpose of grounding? How do lighting rods work? What constitutes a complete electrical circuit?
199
Activity 1 Charged interactions Objectives After performing this activity, you should be able to: 1. 2. 3. 4.
charge a material by friction; observe the behavior of charged objects; distinguish between the two types of charges; and demonstrate how objects can be discharged.
Materials Needed:
Strong adhesive tape (transparent) Smooth wooden table Meter stick Piece of wood (~1 meter long) to hold tape strips Moistened sponge
Procedure: 1.
Using a meter stick, pull off a 40- to 60- cm piece of adhesive tape and fold a short section of it (~1 cm) to make a nonsticky "handle" at that end of the tape.
2.
Lay the tape adhesive side down and slide your finger along the tape to firmly attach it to a smooth, dry surface of a table.
3.
Peel the tape from the surface vigorously pulling up on the handle you have made on one end. See figure below. Make sure that the tape does not curl up around itself or your fingers.
Figure 1. How to peel the tape off the surface 4.
While holding the tape up by the handle and away from other objects, attach the tape to the horizontal wooden piece or the edge of your table. Make sure that the sticky side does not come in contact with other objects. 200
Figure 2. Attaching the tape to a holder 5.
Bring your finger near, but not touching, the nonsticky side of the tape. Is there any sign of interaction between the tape and the finger?
6.
Try this with another object. Is there any sign of interaction between the tape and this object?
7.
Prepare another tape as described in steps 1 to 3.
8.
Bring the nonsticky side of the two charged tapes you prepared near each other. Do you observe any interaction?
9.
Drag a moistened sponge across the nonsticky side of the tapes and repeat steps 5, 6 and 8. Do you still observe any interaction?
10.
Record your observations.
Types of Charges You have learned in previous modules that all matter are made up of atoms or combinations of atoms called compounds. The varying atomic composition of different materials gives them different electrical properties. One of which is the ability of a material to lose or gain electrons when they come into contact with a different material through friction. In activity 1, when you pulled the tape vigorously from the table, some of the electrons from the table’s surface were transferred to the tape. This means that the table has lost some electrons so it has become positively charged while the tape has gained electrons which made it negatively charged. The process involved is usually referred to as charging up the material, and in this particular activity the process used is charging by friction.
201
It is important to remember that during the charging process, ideally, the amount of charge lost by the table is equal to the amount of charge gained by the tape. This is generally true in any charging process. The idea is known as:
The Law of Conservation of Charge Charges cannot be created nor destroyed, but can be transferred from one material to another. The total charge in a system must remain constant.
Electric Force When you brought your finger (and the other object) near the charged tape, you must have observed that the tape was drawn towards your finger as if being pulled by an invisible force. This force is called electric force which acts on charges. An uncharged or neutral object that has balanced positive and negative charges cannot experience this force. We learned from the previous section that the tape is negatively charged. The excess negative charge in the tape allowed it to interact with your finger and the other object. Recall also that when you placed the two charged tapes near each other they seem to push each other away. These observations tell us that there are two kinds of electric force which arises from the fact that there also two kinds of electrical charges. The interactions between the charges are summarized in the following law:
Electrostatic Law Like charges repel and unlike charges attract.
But your finger and the other object are neutral, so how did they interact with the charged tape? Generally, a charged object and an uncharged object tend to attract each other due to the phenomenon of electrostatic polarization which can be explained by the electrostatic law. When a neutral object is placed near a charged object, the charges within the neutral object are rearranged such that the charged object attracts the opposite charges within the neutral object. This phenomenon is illustrated in Figure 3.
202
Figure 3. Polarization of a neutral object
Discharging In Activity 1, after dragging a moistened sponge on the surface of the tape, you must have noticed that the previous interactions you observed has ceased to occur. What happened? The lack of interaction indicates that the electrical force is gone which can only happen when there are no more excess charges in the tape, that is, it has become neutral. The process of removing excess charges on an object is called discharging. When discharging is done by means of providing a path between the charged object and a ground, the process may be referred to as grounding. A ground can be any object that can serve as an “unlimited” source of electrons so that it will be capable of removing or transferring electrons from or to a charged object in order to neutralize that object. Grounding is necessary in electrical devices and equipment since it can prevent the build-up of excess charges where it is not needed. In the next activity, you will use the idea of grounding to discover another way of charging a material.
Activity 2 To charge or not to charge Objective After performing this activity, you should be able to apply the phenomenon of polarization and grounding to charge a material by induction.
Materials Needed:
Styrofoam cup soft drink can balloon
203
Procedure: 1.
Mount the soft drink can on the Styrofoam cup as seen in Figure 4.
Figure 4. Mounting of soft drink can
2.
Charge the balloon by rubbing it off your hair or your classmate’s hair. Note: This will work only if the hair is completely dry.
3.
Place the charged balloon as near as possible to the soft drink can without the two objects touching. Figure 5. Balloon placed near the can
4.
Touch the can with your finger at the end opposite the balloon.
5.
Remove your hand and observe how the balloon and the can will interact.
Figure 6. Touching the can
Q1. What do you think is the charge acquired by the balloon after rubbing it against your hair? Q2. In which part of the activity did polarization occur? Explain. Q3. What is the purpose of touching the can in step #4? Q4. Were you able to charge the soft drink can? Explain how this happened. Q5. Based on your answer in Q1, what do you think is the charge of the soft drink can?
204
Conductors vs. Insulators The behavior of a charged material depends on its ability to allow charges to flow through it. A material that permits charges to flow freely within it, is a good electrical conductor. A good conducting material will allow charges to be distributed evenly on its surface. Metals are usually good conductors of electricity. In contrast to conductors, insulators are materials that hinder the free flow charges within it. If charge is transferred to an insulator, the excess charge will remain at the original location of charging. This means that charge is seldom distributed evenly across the surface of an insulator. Some examples of insulators are glass, porcelain, plastic and rubber. The observations you made had in Activity 2 depended on the fact that the balloon and the Styrofoam are good insulators while the soft drink can and you are good conductors. You have observed that the soft drink can has become charged after you touched one of its ends. The charging process used in this activity is called induction charging, where an object can be charged without actual contact to any other charged object. In the next activity you will investigate another method of charging which depends on the conductivity of the materials
Activity 3 Pass the charge Objective After performing this activity, you should be able to charge a material by conduction.
Materials Needed:
2 styrofoam cups 2 softdrink cans balloon
Procedure: 1.
Repeat all steps of Activity 2.
2.
Let the charged can-cup set-up from Activity 2 touch a neutral can-cup set-up as shown in Figure 7.
205
Figure 7. Putting the two set-ups into contact.
3.
Separate the two set-ups then observe how the charged balloon interacts with the first and second set-up.
Q1. Were you able to charge the can in the second set-up? Explain how this happened. Q2. s it necessary for the two cans to come into contact for charging to happen? Why or why not? Q3. From your observation in step 3, infer the charge acquired by the can in the second set-up. The charging process you performed in Activity 3 is called charging by conduction which involves the contact of a charged object to a neutral object. Now that you have learned the three types of charging processes, we can discuss a natural phenomenon which is essentially a result of electrical charging. You will investigate this phenomenon in the following activity.
Activity 4 When lightning strikes Objectives: After performing this activity, you should be able to: 1. explain how lightning occurs; 2. discuss ways of avoiding the dangers associated with lightning; and 3. explain how a lightning rod functions.
Materials Needed: access to reference books or to the Internet Procedure: 1.
Learn amazing facts about lightning by researching the answers to the following questions: What is a lightning? Where does a lightning originate? How ‘powerful’ is a lightning bolt? Can lightning’s energy be caught stored, and used? How many people are killed by lightning per year? What can you do to prevent yourself from being struck by lightning? Some people have been hit by lightning many times. Why have they survived? How many bushfires are started by lightning strikes? ‘Lightning never strikes twice in the same place.’ Is this a myth or a fact? What are lightning rods? How do they function? 206
As introduced at the beginning of this module, electrical energy has numerous applications. However many of this applications will not be possible unless we know how to control electrical energy or electricity. How do we control electricity? It starts by providing a path through which charges can flow. This path is provided by an electric circuit. You will investigate the necessary conditions for an electric circuit to function in the following activity.
Activity 5 Let there be light! Objectives: After performing this activity, you should be able to: 1. 2.
identify the appropriate arrangements of wire, bulb and battery which successfully light a bulb; and describe the two requirements for an electric circuit to function.
Materials Needed:
3- or 1.5-volt battery 2-meter copper wires/ wires with alligator clips pliers/ wire cutter 1.5- watt bulb/ LED
Procedure: 1.
Work with a partner and discover the appropriate arrangements of wires, a battery and a bulb
that will
make the bulb light.
2.
Once you are successful
in the arrangement, draw a diagram representing your circuit.
3.
Compare your output with other pairs that are successful in their arrangement.
Q1. What difficulties did you encounter in performing this activity? Q2. How does your work compare with other pair’s work? Q3. What was necessary to make the bulb light?
207
Energy Transfer in the Circuit In Activity 5, you have seen that with appropriate materials and connections, it is possible for the bulb to light. We know that light is one form of energy. Where did this energy come from? The law of conservation of energy tells us that energy can neither be created nor destroyed but can be transformed from one form to another. This tells us that the light energy observed in the bulb must have come from the electrical energy or electricity in the circuit. In fact, all electrical equipment and devices are based on this process of transformation of electrical energy into other forms of energy. Some examples are: 1. Flat iron – Electrical energy to thermal energy or heat 2. Electric fan – Electrical energy to mechanical energy 3. Washing machine – electrical energy to mechanical energy. Can you identify other examples?
References “Instructor Materials: Electricity” by American Association of Physics Teachers © 2001. Retrieved from https://aapt.org/Publications/pips_samples/ 2_ELECTRICITY/INSTRUCTOR/099_e4.pdf http://www.physicsclassroom.com/class/estatics/U8L2a.cfm http://museumvictoria.com.au/pages/7567/lightning-room-classroom-activities.pdf http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html
208
209
210
Suggested time allotment: 14 hours
Unit 4 MODULE
1
THE PHILIPPINE ENVIRONMENT
Overview Everything that we see around us makes up our environment. The landforms and bodies of water that make up the landscape, the mountains and valleys, rivers and seas; the climate, the rains brought by the monsoons, the warm, humid weather that we frequently experience; the natural resources that we make use of; every plant and animal that live around us. Truly, the environment is made up of a lot of things. All these things that we find in our surroundings and all the natural phenomena that we observe are not due to some random luck or accident. What makes up our environment is very much related to where our country is on the globe. Or, to say it in a different way, the characteristics of our environment are determined by the location of the Philippines on the planet.
Latitude and Longitude Before we learn about the characteristics of our environment, let us first talk about the location of the Philippines. Where is the Philippines? The Philippines is on Earth, of course, but where exactly is it located? To answer this question, you have to learn a new skill: locating places using latitude and longitude.
Activity 1 Where in the world is the Philippines? (Part I) Objective After performing this activity, you should be able to describe the location of the Philippines using latitude and longitude.
What to use globes
211
What to do 1. Study the image of a globe on the right. Then get a real globe and identify the parts that are labelled in the image. Be ready to point them out when your teachers asks you. 2. After studying the globe and the image on the right, try to define “equator” in your own words. Give your own definition when your teacher asks you. 3. The “northern hemisphere” is that part of the world between the North Pole and the equator. Show the northern hemisphere on the globe when your teacher asks you. 4. Where is the “southern hemisphere”? Show the southern hemisphere on the globe when your teacher asks you.
Figure 1. What does the globe represent?
5. Study the drawing on the right. It shows the lines of latitude. Q1. Describe the lines of latitude. Q2. Show the lines of latitude on the globe when your teacher asks you. Q3. The starting point for latitude is the equator. The equator is at latitude 0° (0 degree). At the North Pole, the latitude is 90°N (90 degrees north). At the South Pole, the latitude is 90°S (90 degrees south). Show the following latitudes when your teacher calls on you: 15°N; 60°N; 30°S; 45°S. Q4. The globe does not show all lines of latitude. If you wish to find 50°N, where should you look?
212
Figure 2. What is the reference line when determining the latitude?
6. Study the drawing on the right. It shows the lines of longitude. Q5. Describe the lines of longitude. Q6. Show the lines of longitude on the globe when your teacher asks you. Q7. The starting point for longitude is the Prime Meridian. The Prime Meridian is at longitude 0°. Show the Prime Meridian on the globe when your teacher asks you. Q8. To the right of the Prime Meridian, the longitude is written this way: 15°E (15 degrees east), 30°E (30 degrees east), and so on. To the Figure 3. What is the left of the Prime Meridian, the reference line when longitude is written as 15°W (15 determining the longitude? degrees west), 30°W (30 degrees west), and so on. On your globe, find longitude 180°. What does this longitude represent? Q9. Not all lines of longitude are shown on a globe. If you want to find 20°W, where should you look? Q10.
The location of a place may be described by using latitude and longitude. To the nearest degree, what is the latitude and longitude of Manila?
Q11.
Compared to the size of the world, Manila is just a tiny spot, and its location may be described using a pair of latitude and longitude. But how would you describe the location of an “area” such as the whole Philippines?
Now you know how to describe the location of a certain place using latitude and longitude. The lines of latitude are also known as parallels of latitude. That is because the lines of latitude are parallel to the equator and to each other. Five lines of latitude have special names. They are listed in the table below. The latitude values have been rounded off to the nearest half-degree. Latitude 0° 23.5°N 23.5°S 66.5°N 66.5°S
Name Equator Tropic of Cancer Tropic of Capricorn Arctic Circle Antarctic Circle
213
Get a globe and find the Tropic of Cancer and the Tropic of Capricorn. Trace the two lines of latitude with a red chalk. The part of the world between the two chalk lines is called the tropics. Countries that are located in this zone experience a tropical climate where the annual average temperature is above 18°C. Now, find the Arctic Circle and the Antarctic Circle on the globe. Trace them with blue chalk. Between the Tropic of Cancer and the Arctic Circle is the northern temperate zone; between the Tropic of Capricorn and the Antarctic Circle is the southern temperate zone. Countries in these zones go through four seasons – winter, spring summer, and autumn. Finally, the areas within the Arctic Circle and Antarctic Circle are called the polar regions or frigid zones. People who choose to live in these areas have to deal with temperatures that never go above 10°C. It is cold all year round and even during the summer months, it does not feel like summer at all. To sum up, the closer the latitude is to the equator, the warmer the climate. The closer it is to the poles, the colder. Thus, it is clear that there is a relationship between the latitude of a place and the climate it experiences, and you will find out why in the next module.
Landmasses and Bodies of Water Using latitude and longitude is not the only way that you can describe the location of a certain area. Another way is by identifying the landmasses and bodies of water that are found in that area. So, what are the landmasses and bodies of water that surround the Philippines? Do the following activity and get to know the surrounding geography.
Activity 2 Where in the world is the Philippines? (Part II) Objective After performing this activity, you should be able to describe the location of the Philippines with respect to the surrounding landmasses and bodies of water.
What to use globe or world map
What to do 1.
Using a globe or a world map as reference, label the blank map below.
214
2.
Your labelled map should include the following: A. Landmasses
B. Bodies of water
Philippine archipelago Asian continent Malay peninsula Isthmus of Kra Indonesian archipelago Australian continent
Philippine Sea South China Sea Indian Ocean Pacific Ocean
Q1. Which bodies of water in the list are found to the west of the Philippines? Q2. Which body of water in the list is located to the east of the Philippines? Q3. Which large landmass is found to the north of the Philippines? 3.
Be ready to show the map with your labels when your teachers asks you.
Figure 4. Where is the Philippines in the map? Why is the Philippines called an archipelago?
215
By now you can say that you really know where the Philippines is. You can now describe its location in two ways: by using latitude and longitude, and by identifying the landmasses and bodies of water that surround it. What then is the use of knowing where the Philippines is located? You will find out in the next section and also in the following module.
Are We Lucky in the Philippines? Planet Earth is made up of different things - air, water, plants, animals, soil, rocks, minerals, crude oil, and other fossil fuels. These things are called natural resources because they are not made by people; rather they are gathered from nature. Sunlight and wind are also natural resources. We use all these things to survive or satisfy our needs. The Philippines is considered rich in natural resources. We have fertile, arable lands, high diversity of plant and animals, extensive coastlines, and rich mineral deposits. We have natural gas, coal, and geothermal energy. Wind and water are also harnessed for electricity generation.
Photo: Courtesy of Michael C. Tan
Photo: Courtesy of Kit Stephen S. Agad
Photo: Courtesy of Cecile N. Sales
Figure 5: What kind of natural resources are shown in the pictures? Do you have similar resources in your area? Why do we have rich natural resources? What geologic structures in the country account for these bounty? Is our location near the equator related to the presence of these natural resources? The next lessons will help you find answers to some questions about natural resources in the country namely, rocks and minerals, water, soil, varied life forms, and energy. How does our latitude position affect the water, soil resources, and biodiversity in the country? What mineral deposits do we have in the country? Where are they located and why only in those places? Given our location, what energy resources are available? Which of our practices in using natural resources are sustainable? Which are not sustainable? 216
How can we help conserve natural resources so that future generations can also enjoy them?
Hopefully, the knowledge and skills acquired in the lessons will help you value your responsibility as a productive citizen so that you can help prevent protected and vulnerable places from being mined, forests from being overcut, and natural resources like metals from ending up in a dumpsite.
Water Resources and Biodiversity The Philippines boasts of many different kinds of natural water forms, such as bays, rivers, lakes, falls, gulfs, straits, and swamps. Because it is made up of islands, the country's coastline (seashore) if laid end-to-end, would measure around 17.5 thousand kilometers. And you know how we are proud of our coastlines! The bodies of water and its surrounding environment not only support the survival of diverse organisms for food but are also used for other economic activities. All these you learned in Araling Panlipunan. In the previous activity you identified two big bodies of water on the west and east side of the country: the Pacific Ocean in the east and south China Sea in the west (sometimes referred to as the West Philippine Sea). These bodies of water are the origin of typhoons which on the average, according to Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA), is about 20 a year. Typhoons and the monsoons (amihan and habagat) bring lots of rain to the Philippines. What is your association with too much rainfall? For some, rain and typhoons result in flooding, landslides, and health related-problems. But water is one of nature’s gifts to us. People need fresh water for many purposes. We use water for domestic purposes, for irrigation, and for industries. We need water to generate electricity. We use water for recreation or its aesthetic value. Many resorts are located near springs, waterfalls or lakes. Where does water in your community come from? You collect them when the rain falls or get them from the river, deep well, or spring. But where does water from rivers, lakes, and springs originate? They come from a watershed – an area of land on a slope which drains its water into a stream and its tributaries (small streams that supply water to a main stream). This is the reason why a watershed is sometimes called a catchment area or drainage basin. It includes the surface of the land and the underground rock formation drained by the stream. From an aerial view, drainage patterns in a watershed resemble a network similar to the branching pattern of a tree. Tributaries, similar to twigs and small branches, flow into streams, the main branch of the tree. Streams eventually empty into a large river comparable to the trunk.
217
Photo: Courtesy of Michael C. Tan
Figure 6. The network of streams in a watershed area is illustrated on the left and a photo of a watershed area is on the right. How does the concept “water runs downhill” apply to a watershed?
Watersheds come in all shapes and sizes. They cross towns and provinces. In other parts of the world, they may cross national boundaries. There are many watersheds in the Philippines basically because we have abundant rainfall. Do you know that Mt. Apo in Davao-Cotabato, Makiling-Banahawin Laguna and Quezon, and Tiwi in Albay are watersheds? You must have heard about La Mesa Dam in Metro Manila, Pantabangan Dam in Pampanga, and Angat Dam in Bulacan. These watersheds are sources of water of many communities in the area. The Maria Cristina Falls in Iligan City is in a watershed; it is used to generate electricity. Locate these places in your map. Ask elders where the watershed is in or near your area? Observe it is used in your community. But watersheds are not just about water. A single watershed may include combination of forest, grassland, marshes, and other habitats. Diverse organisms in the Philippines are found in these areas! Being a tropical country, the Philippines has abundant rainfall, many bodies of water, and lots of sunshine. The right temperature and abundant rainfall explain partly why our country is considered to be a megadiverse country. This means that we have high diversity of plants and animals, both on land and in water (Philippine Clearing House Mechanism Website, 2012). Reports show that in many islands of the Philippine archipelago, there is a high number of endemic plants and animals (endemic means found only in the Philippines). The country hosts more than 52,177 described species of which more than half is found nowhere else in the world. They say that on a per unit area basis, the Philippines shelters more diversity of life than any other country on the planet. For now remember that the main function of a watershed is the production of a continuous water supply that would maintain the lifeforms within it and in the area fed by its stream. Later you will learn that besides supporting the survival of varied life forms, abundant water in the country is important in moderating temperature. This topic will be discussed later.
218
Have you ever asked yourself the following questions? If we have abundant rainfall to feed watersheds, why do we experience drought some parts of the year? What factors affect the health of a watershed? Is there a way of regulating the flow of water in watershed so that there will be enough for all throughout the year? What can people do to keep watersheds ‘healthy’? Find out about these in the next activity.
Activity 3 What are some factors that will affect the amount of water in watersheds? Objective You will design a procedure to show how a certain factor affects the amount of water that can be stored underground or released by a watershed to rivers, lakes and other bodies of water.
What to do 1.
In your group, choose one factor that you want to investigate. a. b. c. d.
Vegetation cover Slope of the area Kind of soil Amount of rainfall
2.
Identify the variables that you need to control and the variable that you will change.
3.
Design a procedure to determine the effect of the factor you chose on watersheds.
4.
Be ready to present your design in the class and to defend why you designed it that way.
Soil Resources, Rainfall and Temperature Recall in elementary school science that soil is formed when rocks and other materials near the Earth’s surface are broken down by a number of processes collectively called weathering. You learned two types of weathering: the mechanical breaking of rocks or physical weathering, and the chemical decay of rocks or chemical weathering. Let us review what happens to a piece of rock when left under the Sun and rain for a long time. Do the next activity.
219
Activity 4 How are soils formed from rocks? Objectives 1. 2.
Using the information in the table, trace the formation of soil from rocks. Identify the factors acting together on rocks to form soil.
What to use Drawing pens
What to do 1. Processes involved in soil formation are listed in the table below. Read the descriptions of the processes and make your own illustrations of the different processes. Draw in the designated spaces. 2. Use the descriptions and your drawings to answer the following questions. Q1. What are the factors that act together on rocks to form soil? Q2. What does the following sentence mean, “Soils were once rocks”? Processes of soil formation When a piece of rock is exposed to the Sun, its outer part expands (becomes bigger) because it heats up faster than the inner part (Drawing A).
Illustrations of processes Drawing A
On cooling, at night time, the outer part of the rock contracts or shrinks because the outer part of the rock cools faster than the inner portion (Drawing B). The process of expansion and contraction are repeated over the years and produce cracks in the rock causing the outer surface to break off. Once broken, water enters the cracks causing some minerals to dissolve. The rock breaks apart further. (Drawing C).
Drawing B
Drawing C
220
Processes of soil formation Air also enters the cracks, and oxygen in the air combines with some elements such as iron to produce iron oxide (rust or kalawang) which is brittle and will easily peel off. In a similar way, carbon dioxide from the air reacts with water to form an acid causing the rock to soften further. Once soft and broken, bacteria and small plants start to grow in the cracks of the rock (Drawing D).
Illustrations of processes Drawing D
After some time, the dead plants and animals die and decay causing the formation of more acidic substances which further breaks the rocks. The dead bodies of plants and animals are acted upon by microorganism and breakdown into smaller compounds while the minerals from the rock return to the soil.
Soil covers the entire Earth. Temperature, rainfall, chemical changes, and biological action act together to continuously form soil. Climate, expressed as both temperature and rainfall effects, is often considered the most powerful soil-forming factor. Temperature controls how fast chemical reactions occur. Many reactions proceed more quickly as temperature increases. Warm-region soils are normally more developed or more mature than cold-region soils. Mature soils have more silt and clay on or near the surface. Thus, soils in the tropical areas are observed to sustain various farming activities and account for why the primary source of livelihood in the Philippines and other countries in the tropical region is their fertile land. What is the effect of very little rainfall on food production? Climate (temperature and rainfall) is a significant factor not only in soil formation but also in sustaining diversity of plants and animals in the country. On the other hand, water also directly affects the movement of soluble soil nutrients from the top soil to deep under the ground (leaching). These nutrients may no longer be available to shallow rooted plants. Acidic rainwater may also contribute to the loss of minerals in soil resulting in low yield. So rainfall determines the kind of vegetation in an area. In turn, the degree of vegetation cover, especially in sloping areas, determines how much soil is removed. Are there ways to protect soil resources? 221
Rocks and Mineral Resources History tells us that rocks have been used by humans for more than two million years. Our ancestors lived in caves; they carved rocks and stones to make tools for hunting animals, cultivating crops, or weapons for protection. Rocks, stones, gravel, and sand were and are still used to make roads, buildings, monuments, and art objects.
http://commons.wikimedia.org/wiki/File:DirkvdM_rocks.jpg
http://en.wikipedia.org/wiki/File:Pana_Banaue_Rice_Terr aces.jpg
Figure 7. What are the features of the rocks? What environmental factors may have caused such features?
Figure 8. What kind of tools do you think were used to build the Rice Terraces? Why are terraces useful?
The mining of rocks for their metal content has been considered one of the most important factors of human progress. The mining industry has raised levels of economy in some regions, in part because of the kind of metals available from the rocks in those areas.
Activity 5 Where are the mineral deposits in the Philippines? Mineral deposits can be classified into two types: metallic and non-metalllic. You have already learned the symbols of some metals and nonmetals. Review them before you do the activity.
Objectives After performing this activity, you will be able to 1. locate the metallic mineral deposits across the country;
222
2. find out what geologic features are common in areas where the deposits are found; 3. give a possible reason/s for the association between metallic mineral deposits and geologic features in the country; and 4. infer why your area or region is rich or not rich in metallic mineral deposits.
What to use Figure 9: Metallic Deposits Map of the Philippines Figure 10: Map of Trenches and Faults in the Philippines Figure 11: Map of Volcanoes in the Philippines 2 pieces of plastic sheet used for book cover, same size as a book page Marking pens (two colors, if possible)
What to do Part I 1. Familiarize yourself with the physical map of the Philippines. Identify specific places of interest to you in the different regions. 2. In your notebook, make a four-column table with headings similar to Table 1. Table 1: Metallic Minerals in the Philippines and Their Location Geologic Metal, in Metal, in Words Province/Region Structure Near Symbols Where the the Location of (Example: Au) Metals are the Metallic Found Deposits (1) (2) (3) (4)
3. As a group, study the Metallic Deposits Map of the Philippines. See Figure 9. In the map you will see symbols of metals. Fill in the information needed in Columns 1 and 2 of your own table. 4. Check with each other if you have correctly written the correct words for the symbol of the metals. Add as many rows as there are kinds of metals in the map. 5. Analyze the data in Table 1. Q1. Identify five metals which are most abundant across the country. Put a number on this metal (1 for most abundant, 2 next abundant, and so on). Q2. Record in Column 3 where the five most abundant metals are located. 223
Figure 9. Metallic Deposits in the Philippines
224
Figure 10. Trenches and Faults in the Philippines
225
Figure 11. Volcanoes in the Philippines
226
Part II 1.
Get two plastic sheets. On one sheet, trace the outlines of the trenches and faults from Figure 10. On the other sheet, trace the location of volcanoes from Figure 11.
2.
Place the Trench and Fault plastic sheet over the Metallic Deposits map.
3. Place the Volcanoes plastic sheet over the two maps. Q3. What geologic structures are found near the location of the metallic deposits? Write trenches, faults or volcanoes in column 4 of Table 1. Q4. Write a statement to connect the presence of metallic deposits with trenches or volcanic areas. Q5. Why do you think are metallic deposits abundant in places where there are trenches or volcanoes? 4. Look for your province in the map. Q6. Are there metallic deposits in your area? Q7. What could be reason for the presence or absence of metallic deposits in your area? You can download the detailed map of Trenches, Faults and volcanoes in the Philippines from the website of Phivolcs. Q8. If there are metallic deposits, what activities tell you that there are indeed deposits in or near your area/province?
The important metallic minerals found in various parts of the Philippines include gold, copper, iron, chromite (made up of chromium, iron, and other metals), nickel, cobalt, and platinum. The most productive copper and gold producers in the Philippines are found in Baguio, the province of Benguet, and in Surigao-Davao areas. Major producers of nickel are in Palawan and Surigao (DENR Website, 2012). Metals are important. The properties of metals make them useful for specific purposes. You learned these in Quarter 1. Iron is the main material for steel bars used in buildings and road construction. Copper is used in making electrical wires. Tin is the material for milk cans and other preserved food products. Nickel is mixed with copper or other metals to form stainless cooking wares. Gold is important in making jewelry. What other metals are you familiar with? What are the uses of aluminum? What metal is used to make GI sheets for roofing? What metals are used to make artificial arms or legs? Are metals used in chairs and other furniture? Do you know that some dentists use gold for filling teeth cavities? Look around and find how versatile metals are.
227
The Philippines has also varied nonmetallic resources including sand and gravel, limestone, marble, clay, and other quarry materials. Your teacher will show you a map of the nonmetallic deposits in the Philippines. Locate your area and determine what nonmetallic deposits are found there. How are these deposits recovered? How are they used in your community? For example: What are the uses of sand, gravel, or clay? How are marble stones used? Think of other nonmetals and their uses!
Copper – iron ore
Iron filings
Quartz
Copper ore
Figure 12. From the drawing, what are ores? Have you noticed that a piece of ore can have more than one kind of mineral in it? Do you know that the Philippines is listed as the 5th mineral country in the world, 3rd in gold reserves, 4th in copper, and 5th in nickel! The ores (mineralbearing rocks) are processed out of the country to recover the pure metal. We buy the pure metal. Is this practice advantageous to the Philippines? Why or why not? The richness of the Philippines in terms of mineral resources is being attributed to its location in the so-called Pacific Ring of Fire. See Figure 13. This area is associated with over 450 volcanoes (small triangles in the map) and is home to approximately 75% of the world's active volcanoes. Why are there minerals where there are volcanoes? Geologists (scientists who study Figure 13. Besides the Philippines, what the Earth and the processes that occur other countries are in the Ring of Fire? in and on it) explain that there is a Do you think they are also rich in mineral continuous source of heat deep under resources? the Earth; this melts rocks and other materials (link to usgs website).The mixture of molten or semi-molten materials is called magma. Because magma is hotter and lighter than the surrounding rocks, it rises, melting some of the rocks it passes on the way. If the magma finds a way to the surface, it will erupt as lava. Lava flow is observed in erupting volcanoes. But the rising magma does not always reach the surface to erupt. Instead, it may slowly cool and harden beneath the volcano and form different kinds of igneous rocks. Under favorable temperature and pressure conditions, the metal-containing rocks continuously melt and redeposit, eventually forming rich-mineral veins. 228
Though originally scattered in very small amounts in magma, the metals are concentrated when magma convectively moves and circulates ore-bearing liquids and gases. This is the reason why metallic minerals deposits such as copper, gold, silver, lead, and zinc are associated with magmas found deep within the roots of extinct volcanoes. And as you saw in the maps, volcanoes are always near trenches and faults! You will learn more of this later. For now you must have realized that the presence of mineral deposits in the Philippines is not by accident. It is nature’s gift. If before, your association with volcanoes and trenches is danger and risk to life and property, now you know that the presence of volcanoes, trenches and other geological structures is the reason for the rich mineral deposits in the country. The existence of volcanoes also explains why the Philippines is rich in geothermal energy (heat from the Earth). Energy resources will be discussed in the next section.
Energy Resources The abundance of some metal resources in the Philippines is related to geologic structures, specifically the presence of volcanoes and trenches in the country. The year-round warm temperature and availability of water are effects of our geographic location. The tropical climate and the geological conditions also provide several possibilities to get clean and cheap energy. Do you know which energy resources are due to these factors? Were the following included in your list- solar energy, heat from the ground (geothermal energy), hydrothermal energy from falling water), wind energy, and natural gas? Solar energy is free and inexhaustible. This energy source will be discussed in a later science subject. Geothermal energy was briefly introduced in the lesson on mineral resources and their location. The Philippines ranked second to the United States in terms of geothermal energy deposits. Geothermal power plants are located in Banahaw-Makiling, Laguna, Tiwi in Albay, Bacman in Sorsogon, Palimpinon in Negros Occidental, Tongonan in Leyte, and Mt. Apo side of Cotabato.
http://commons.wikimedia.org/wiki/File:Hot_Spring.jpg
Figure 14. Do you know that heat from the Earth may escape as steam in a hot spring?
Try to locate places with geothermal power plants in your map? Does your area have geothermal energy deposits? How do you know?
229
Hydrothermal or hydroelectric power plants use water to generate electricity. They provide for 27% of total electricity production in the country. Ambuklao in Benguet, Mt Province, Agus in Lanao del Sur and Agus in Lanao del Norte are large hydrothermal power plants. Small hydroelectric power plants are in Caliraya, Laguna, Magat in Isabela, Loboc in Bohol, and other places. Used water from hydropower plants flows through irrigation systems. Many of the reservoir areas are used for sport activities.
Photograph courtesy of National Power Corporation, retrieved from http://www.industcards.com/hydrophilippines.htm
Figure 15. How is water used to generate electricity?
Again, locate places with hydroelectric power plants in your map? Does your area have hydroelectric power plants? What other uses do you have for water in these areas? Natural gas is a form of fossil fuel, so are coal and crude oil (sometimes called petroleum). Fossil fuels were formed from plants and animals that lived on Earth millions of years ago. They are buried deep in the Earth. Natural gas and oil are taken from the deep through oil rigs while coal is extracted through mining. Fossil fuels are used to produce electricity and run vehicles and factory machines. Did you know that petroleum is the raw material for making plastics? In the Philippines, we have coal and natural gas deposits. Coal is a black or brownish black, solid rock that can be burned. It contains about 40% noncombustible components, thus a source of air pollution when used as fuel. Coal deposits are scattered over the Philippines but the largest deposit is located in Semirara Island, Antique. Coal mines are also located in Cebu, Zamboanga Sibuguey, Albay, Surigao, and Negros Provinces.
Figure 16. The black bands in the picture are coal deposits. Coal is not like the charcoal you use for broiling fish or barbecue. What do you think is the difference?
Our natural gas deposits are found offshore of Palawan. Do you know where this place is? The Malampaya Deepwater Gas-to-Power Project employs ‘state-of-the-art deepwater technology’ to draw natural gas from deep beneath Philippine waters. The gas fuels three natural gas-fired power stations to provide 40-45% of Luzon's power 230
generation requirements. The Department of Energy reports that since October 2001, the Philippines has been importing less petroleum for electricity generation, providing the country foreign-exchange savings and energy security from this clean fuel. Natural gas is considered clean fuel because when burned, it produces the least carbon dioxide, among fossil fuels. CO2 is naturally present in air in small amounts. However, studies show that increase in carbon dioxide in the atmosphere results in increase in atmospheric temperature, globally. You will learn about global warming in the next module. Did you know that in Ilocos Province, giant wind mills as shown in Figure 5 of this module are used to generate electricity? In Quirino, Ilocos Sur the electricity generated from wind mills runs a motorized sugarcane press for the community's muscovado sugar production? This project is a joint effort between the local farmers and local organizations with support from Japan. In Bangui, Ilocos Norte, the windmills as high as 50 meters not only help improve the tourism in Ilocos but it also provides 40% of the energy requirements for electricity in the entire province. This proves that we do not have to be dependent on fossil fuel in our country. What do you think are the environmental conditions in Ilocos Sur and Ilocos Norte that allow them to use wind power for electricity? Do you think there are places that have these conditions? Support your answers.
Conserving and Protecting Natural Resources There are two types of natural resources on Earth - renewable and nonrenewable. What is the difference between these two kinds of resources? The food people eat comes from plants and animals. Plants are replaced by new ones after each harvest. People also eat animals. Animals have the capacity to reproduce and are replaced when young animals are born. Water in a river or in a well may dry up. But when the rain comes the water is replaced. Plants, animals, and water are resources that can be replaced. They are renewable resources. Most plants grow in top soil. Rain and floods wash away top soil. Can top soil be replaced easily? Soil comes from rocks and materials from dead plants and animals. It takes thousands of years for soil to form. Soil cannot be replaced easily, or it takes a very long time to replace. It is a nonrenewable resource. Metals like copper, iron, and aluminum are abundant on Earth. But people are using them up fast. They have to dig deeper into the ground to get what they need. Coal, oil and natural gas (fossil fuels) were formed from plants and animals that lived on Earth millions of years ago. It takes millions of years for dead plants and animals to turn into fossil fuels. Soil, coal, oil and natural gas are nonrenewable resources.
231
Before you do Activity 6, think of these sentences: “Too much is taken from Earth!" and "Too much is put into Earth." You may write up a short essay about your understanding of the sentences.
Activity 6 How do people destroy natural resources? Objectives 1. 2.
Identify the effects of some human activities on natural resources. Suggest ways to reduce the effects.
What to Do 1.
Study Table 2 and tell if you have observed the activities listed in your locality.
Table 2. Ways People Destroy Natural Resources Activities Effects on Natural Resources (1) (2) When roads are built, mountains are blown off using dynamite. Rice fields are turned into residential or commercial centers. People cut too many trees for lumber or paper or building houses. More factories are being built to keep up with the demands of a fast growing population and industrialization. Too much mining and quarrying for the purpose of getting precious metals and stones and gravel. Some farmers use too much chemical fertilizers to replenish soil fertility.
Damage natural habitats and/or kill plants and animals.
Too much fertilizer destroys the quality of the soil and is harmful to both human and animals.
Plastics and other garbage are burned. Cars, trucks, and tricycles that emit dark smoke (smoke belchers) are allowed to travel. Other activities 2.
Discuss the effects of these activities on natural resources.
3.
Write the effects on the column opposite the activities. An activity may have more than one effect. Some of the effects have already been listed in the table.
232
4.
Do you know of other activities that destroy or cause the depletion of natural resources? Add them to the list and fill the corresponding effect in column 2.
5.
What can you do to conserve resources?
Protecting Resources in Your Own Way All resources used by humans, including fuels, metals, and building materials, come from the Earth. Many of these resources are not in endless supply. It has taken many thousands and millions of years to develop and accumulate these resources. To conserve natural resources is to protect or use them wisely without wasting them or using them up completely. Conserving natural resources can make them last and be available for future generations. This is what sustainability of natural resources means. Each one of us should think about how to make things sustainable. Remember: The lives of future generations depend on how we use natural resources today.
Activity 7 Are you ready for “Make-a-Difference” Day? This activity involves you in hands-on activities that help you learn more about reducing waste, reusing materials instead of throwing them away, recycling, composting, and conserving natural resources and energy. There are many activities that you can include: conducting a "waste-free lunch" or building art materials out of cans, bottles, and other recyclable trash. Depending on the location and nature of your school, you might want to include river cleanup, trail maintenance, or tree planting. Or, you can mix these activities with a poster making contest for use in the campaign on non-use of plastic bags for shopping and/or marketing.
What to do 1.
In your group, make a list of what is done in your school that help conserve natural resources. Discuss your list before finalizing the report.
2.
Make another list of what is done in your school that do not help conserve natural resources. For example, do you still have lots of things in the trash can or on the ground? What are they? What is being done with them?
3.
Come up with a one-day plan on what else can be done in school to conserve natural resources. Present your plan to the class.
233
4.
Based on the group presentation, decide which part in the plans will be adopted or adapted to make a class plan. The plan should consider the following: Easy to follow Who will be responsible for making the plan happen What should be done if the people responsible for making the plan happen will not or cannot do it What natural resources will be conserved Schedule of activities to include monitoring Why you think this plan is the best idea
5.
With your teacher’s permission, make an appointment with your principal to present your plan and to solicit support. Maybe she might recommend the “Make-a-Difference” Day for the whole school!
Hopefully, the “Make-a-Difference” Day will engage you in a variety of environmental activities that help foster not only an appreciation for the environment and the resources it provides but also develop a life-long environmental stewardship among your age group.
Links and Other Reading Materials gdis.denr.gov.ph (Geohazard Map) http://www.phivolcs.dost.gov.ph http://www.jcmiras.net/surge/p124.htm (Geothermal power plants in the Philippines) http://www.industcards.com/hydro-philippines.htm (Hydroelectric power plants in the Philippines)
234
Suggested time allotment: 12 hours
Unit 4 MODULE
2
SOLAR ENERGY AND THE ATMOSPHERE
In the previous module, you learned that the presence of different natural resources in the Philippines is related to the country’s location. It was also mentioned that the climate in a certain area depends on its latitude. In this module, you are going to learn more about how the location of the Philippines influences its climate and weather. To prepare you for this lesson, you must first learn about the envelope of air that surrounds the Earth where all weather events happen – the atmosphere.
Activity 1 What is the basis for dividing Earth’s atmosphere into layers? Earth’s atmosphere is divided into five layers. What is the basis for subdividing the atmosphere?
Objectives You will be able to gather information about Earth’s atmosphere based on a graph. Specifically, you will: 1. 2. 3.
describe the features of each of the five layers; compare the features of the five layers; and explain the basis for the division of the layers of the atmosphere.
Figure 1. What are the layers of the atmosphere?
235
What to use
Graph in Figure 1 A ruler, if available
What to do 1.
Study the graph.
Q1. Q2. Q3. Q4. Q5.
What are the five layers? Estimate the height of each layer. Describe the graph for each layer. In which layer is temperature increasing with increasing altitude? In which layer is temperature decreasing with increasing altitude? What is the relationship between temperature and height in the - troposphere? - stratosphere? - mesosphere? - thermosphere? - exosphere? Q6. Observe the whole graph. What is the basis for the division of Earth’s atmosphere? Q7. From the graph, can you generalize that the higher the layer of the atmosphere (that is closer to the Sun), the hotter the temperature? Why or why not? Q8. What other information about Earth’s atmosphere can you derive from the graph? 2.
Read the succeeding paragraphs and think of a way to organize and summarize the data about the atmosphere from the graph and the information in the discussion that follows.
The troposphere is the layer closest to Earth’s surface. The temperature just above the ground is hotter than the temperature high above. Weather occurs in the troposphere because this layer contains most of the water vapor. Remember the water cycle? Without water, there would be no clouds, rain, snow or other weather features. Air in the troposphere is constantly moving. As a result, aircraft flying through the troposphere may have a very bumpy ride – what we know as turbulence. People who have used the airplane for travelling have experienced this especially when there is a typhoon in areas where the plane passes through. The stratosphere is the layer of air that extends to about 50 km from Earth’s surface. Many jet aircraft fly in the stratosphere because it is very stable. It is in the stratosphere that we find the ozone layer. The ozone layer absorbs much of the Sun’s harmful radiation that would otherwise be dangerous to plant and animal life. The layer between 50 km and 80 km above the Earth’s surface is called the mesosphere. Air in this layer is very thin and cold. Meteors or rock fragments burn up in the mesosphere. 236
The thermosphere is between 80 km and 110 km above the Earth. Space shuttles fly in this area and it is also where the auroras are found. Auroras are caused when the solar wind strikes gases in the atmosphere above the Poles. Why can we not see auroras in the Philippines? The upper limit of our atmosphere is the exosphere. This layer of the atmosphere merges into space. Satellites are stationed in this area, 500 km to 1000 km from Earth. To summarize what has been discussed: More than three quarters of Earth’s atmosphere is made up of nitrogen while one fifth is oxygen. The remaining 1% is a mixture of carbon dioxide, water vapor, and ozone. These gases not only produce important weather features such as cloud and rain, but also have considerable influence on the overall climate of the Earth, through the greenhouse effect and global warming.
What is the Greenhouse Effect? In order to understand the greenhouse effect, you need to first understand how a real greenhouse works. In temperate countries, a greenhouse is used to grow seedlings in the late winter and early spring and later, planted in the open field when the weather is warmer. Greenhouses also protect plants from weather phenomena such snowstorm or dust storms. In tropical countries, greenhouses are used by commercial plant growers to protect flowering and ornamental plants from harsh weather conditions and insect attack. Greenhouses range in size from small sheds to very large buildings. They also vary in terms of types of covering materials. Some are made of glass while others are made of plastic.
Activity 2 Does a greenhouse retain or release heat? Objectives The activity will enable you to 1. 2. 3.
construct a model greenhouse. find out if your model greenhouse retains heat relate the concept of greenhouse to the increasing temperature of Earth’s atmosphere.
237
What to use
2-liter plastic soft drink bottle 2-plastic containers to serve as base of the bottles CAUTION knife or scissors transparent tape two alcohol thermometers one reading lamp (if available), otherwise bring the setups under the Sun
Be careful when handling sharp objects like knife or scissors and breakable equipment like thermometer.
What to do Constructing the model greenhouse For each model greenhouse you will need a two-liter plastic soft drink container (with cap) and a shallow plastic container for the base. 1.
Remove the label of the soft drink bottle but keep the cap attached.
2.
Cut off carefully, the end of the bottle approximately 5-6 cm from the bottom. Dispose of the bottom piece.
3.
Place the bottle with cap in the plastic base. This is your model greenhouse. Label it Bottle A.
4.
Use scissors or knife to cut several elongated openings or vents (1.5 x 5.0 cm) on the sides of Bottle B. Leave Bottle A intact.
5.
Tape a thermometer onto a piece of cardboard. Make sure that the cardboard is longer than the thermometer so that the bulb will not touch the plastic base. Make two thermometer setups, one for Bottle A and another for Bottle B. Place one thermometer setup in each bottle.
238
Figure 2. How to construct a model greenhouse 6.
7.
Place both bottles approximately 10 cm away from the lamp. DO NOT turn on the lamp yet. Q1. Predict which bottle will get hotter when you turn on the light or when they are exposed to the Sun. How will you know that one bottle is hotter than the other? Q2. Write down your prediction and the reason why you predicted that way. Turn on the light and begin collecting data every five minutes for 25 minutes. (Note: But if you have no lamp, place the setups under the Sun. Read the temperature every 20 minutes for over two hours.)
NOTE: If you have no lamp, bring the setups outside the classroom under the Sun where they will not be disturbed.
8.
Record the temperature readings of Bottle A and Bottle B in your notebook.
9. Q3. Q4. Q5. Q6. Q7. Q8. Q9.
Graph your data separately for Bottles A and B. What variable did you put in the x-axis? In the y-axis? Why did you put these data in the x and y axes, respectively? Describe the graph resulting from observations in Bottle A. Describe the graph resulting from observations in Bottle B. Explain the similarities in the graphs of Bottles A and B. Explain the differences in the graphs of Bottles A and B. Does this activity help you answer the question in the activity title: Do greenhouses retain heat? What is the evidence?
239
Greenhouses allow sunlight to enter but prevent heat from escaping. The transparent covering of the greenhouse allows visible light to enter without obstruction. It warms the inside of the greenhouse as energy is absorbed by the plants, soil, and other things inside the building. Air warmed by the heat inside is retained in the building by the roof and wall. The transparent covering also prevents the heat from leaving by reflecting the energy back into the walls and preventing outside winds from carrying it away. The Earth’s atmosphere is compared to a greenhouse. You know that besides nitrogen and oxygen, Earth’s atmosphere contains trace gases such as carbon dioxide, water vapor, methane, and ozone. Like the glass in a greenhouse, the trace gases have a similar effect on the Sun’s rays. They allow sunlight to pass through, resulting in the warming up of the Earth’s surface. But they absorb the energy coming from the Earth’s surface, keeping the Earth’s temperature suitable for life on Earth. The process by which the Earth’s atmosphere warms up is called ‘greenhouse effect,’ and the trace gases are referred to as ‘greenhouse gases.’
https://sites.google.com/site/glowar88/all-about-global-warming/1-what-is-global-warming
Figure 3. Why are greenhouse gases like the glass in the greenhouse? The ‘greenhouse effect’ is a natural process and it warms the Earth. Without the greenhouse effect, Earth would be very cold, too cold for living things, such as plants and animals. To further understand the effect of greenhouse gases look at Figure 4. It contains some data about Venus and Earth, planets that are almost of the same size and if you remember from elementary school science, are near each other, so they are called twin planets. The composition of atmosphere and the average surface 240
temperature of the two planets are also given. Why is the average temperature of Venus very much higher than that of Earth? What could have caused this phenomenon? Both Earth and Venus have carbon dioxide, a greenhouse gas, in their atmospheres. The small amount of carbon dioxide on Earth’s gives the right temperature for living things to survive. With the high surface temperature of Venus due to its high carbon dioxide concentration, do you think life forms like those we know of could exist there? Why or why not? Figure 4. What gas is present in the atmosphere of Venus that explains its high surface temperature?
Is Earth Getting Warmer? What is the Evidence? Studies have shown that before 1750 (called the pre-industrialization years), carbon dioxide concentration was about 0.028 percent or 280 parts per million (ppm) by volume. The graph below shows the concentration of carbon dioxide from 1958 to 2003. What information can you derive from the graph? Recent studies report that in 2000-2009, carbon dioxide rose by 2.0 ppm per year. In 2011, the level is higher than at any time during the last 800 thousand years. Local temperatures fluctuate naturally, over the past 50 years but the average global temperature has increased at the fastest rate in recorded history. So what if there is increasing emission of greenhouse gases like carbon dioxide into the atmosphere? What is the problem with a small increase in carbon dioxide concentration in the atmosphere?
http://en.wikipedia.org/wiki/File:Mauna_Loa_Carbon_Dio xide-en.svg#file
Figure 5. Carbon dioxide measurements in Mauna Loa Observatory, Hawaii
241
More carbon dioxide means that more heat is trapped in Earth’s atmosphere. More heat cannot return back into space. More heat trapped by the carbon dioxide means a warmer Earth. The increasing temperature phenomenon is known as ‘global warming’. Global means that all countries and people around the world are affected even if that country is not a major contributor of greenhouse gases. Many scientists now agree that many human activities emit more greenhouses gases into the atmosphere, making the natural greenhouse effect stronger. Scientists are also saying that if we carry on polluting the atmosphere with greenhouse gases, it will have a dangerous effect on the Earth.
Sources of Greenhouse Gases Carbon dioxide is naturally produced when people and animals breathe. Plants and trees take in and use carbon dioxide to produce their own food. Volcanoes also produce carbon dioxide. Methane comes from grazing animals as they digest their food and from decaying matter in wet rice fields. Ozone is also naturally present in the stratosphere. But human activities emit a lot of greenhouse gases into the atmosphere. Study Figure 7.
http://en.wikipedia.org/wiki/File:Global_Carbon_Emission_by_Type .png
Figure 6. Does burning of fossil fuels raise the carbon dioxide concentration in the atmosphere?
Which fossil fuel has the highest contribution to carbon dioxide concentration in the atmosphere?
242
What human activities use this fuel? List at least three. Recall Module 1. What kind of fossil fuels are used in the Philippines? Are we also contributing to the increase in carbon dioxide concentration in the atmosphere? Why or why not? Carbon dioxide comes from the burning of fossil fuel such as coal, crude oil and natural gas. Cutting down and burning of trees releases carbon dioxide. Methane can also be released from buried waste. For example, the left-over food, garden wastes, and animal wastes collected from our homes are thrown into dumpsites. When lots of wastes are compressed and packed together, they produce methane. Coal mining also produces methane. Another group of greenhouse gases includes the chlorofluorocarbons or CFCs for short. CFCs have been used in spray cans as propellants, in refrigerators as refrigerants, and in making foam plastics as foaming agents. They become dangerous when released into the atmosphere, depleting the ozone layer. For this reason, their use has been banned around the world. What have you learned about the atmosphere? There are natural processes in the atmosphere that protect and sustain life on Earth. For example, the greenhouse effect keeps temperature on Earth just right for living things. For as long as the concentration of greenhouse gases are controlled, we will have no problem. But human beings activities have emitted greenhouse gases into the atmosphere, increasing their levels to quantities that have adverse effects on people, plants, animals and the physical environment. Burning of fossil fuels, for example, has increased levels of carbon dioxide thus trapping more heat, increasing air temperature, and causing global warming. Such global phenomenon is feared to melt polar ice caps and cause flooding to low-lying areas that will result to reduction in biodiversity. It is even feared that global warming is already changing climates around the globe, causing stronger typhoons, and creating many health-related problems. You will learn more about climate change later.
Common Atmospheric Phenomena In the next section, you will learn two concepts that will help you understand common atmospheric phenomena: why the wind blows, why monsoons occur, and what is the so-called intertropical convergence zone. All of these are driven by the same thing: the heat of the Sun or solar energy. Thus, we begin by asking, what happens when air is heated?
243
Activity 3 What happens when air is heated? Objective After this activity, you should be able to explain what happens when air is heated.
What to use two paper bags candle long straight stick match masking tape chair Figure 7. Setup for Activity 3
What to do 1.
Attach a paper bag to each end of the stick (see drawing above). The open end of each bag should be facing down.
2.
Balance the stick with the paper bags on the chair (see drawing below.)
3.
Make a prediction: what do you think will happen if you place a lighted candle under the open end of one of the bags?
4.
Now, light the candle and place it below one of the bags. Caution: Do not place the candle too close to the paper bag. It may catch fire. Be ready with a pail of water or wet rag just in case. Figure 8. Balance the stick with paper bags on a chair.
244
Q1. Was your prediction accurate? Describe what happened. Q2. Can you explain why?
Figure 9. What will happen when a lighted candle is placed under one of the bags? This is the first concept that you need to know: Warm air rises. Now, try to answer the following question. When warm air is rising, what is its effect on the air in the surroundings? Will the air in the surroundings stay in place? Or will it be affected in some way by the rising air? Do the following activity and find out.
Activity 4 What happens to the air in the surroundings as warm air rises? Objective After performing this activity, you should be able to explain what happens to the air in the surroundings as warm air rises.
What to use box scissors cardboard tube clear plastic
candle match smoke source (ex. mosquito coil) Figure 10. Setup for Activity 4
What to do Pre-activity
Make two holes in the box: one hole on one side and another hole on top (see drawing). Place the cardboard tube over the hole on top and tape it in place. Make a window at the front side of the box so you can see inside. Cover the window with clear plastic to make the box airtight.
245
Activity proper 1.
Open the box and place the candle directly below the hole on top. Light up the candle and close the box.
2.
Make a prediction: What do you think will happen if you place a smoke source near the hole?
3.
Now, place the smoke source near the hole.
Q1. Was your prediction accurate? Q2. What happened? Q3. Can you explain why?
Figure 11. What happens to the smoke when the source is placed near the hole?
What Makes the Air Move? As you have seen in the activity, air in the surroundings can be affected by rising warm air. The drawing below shows how this happens. First, the air above the candle becomes warm because of the flame. What happens to this warm air? It rises. As warm air rises, what happens to the air in the surroundings? It will move toward the place where warm air is rising. But you cannot see air, how can you tell that it is moving? Did you see smoke from the mosquito coil? The movement of the smoke shows the movement of the air.
Figure 12. Air in the surroundings move toward the place where warm air is rising.
246
Let us now relate what happened in the activity to what happens in nature. During the day, the surface of the Earth becomes warm because of the Sun. Some parts of the Earth will warm up more quickly than others. Naturally, the air above the warmer surfaces will also become warm. What happens to the warm air? Just like in the activity, it will rise. How is the air in the surroundings affected? It will move toward the place where warm air is rising. This is the other concept that you need to know: Air moves toward the place where warm air is rising. Whenever we feel the air moving, that means that somewhere, warm air is rising. And the air around us moves toward the place where warm air is rising. Do you remember that ‘moving air’ is called wind? Every time you feel the wind, it means that air is moving toward the place where warm air is rising. Strictly speaking, wind is air that is moving horizontally. Let us use now the two concepts you have learned to explain other things. You know that the surface of the Earth is made basically of two things: land and water. When the Sun’s rays strike land and water, do they heat up as fast as each other? Do land and water absorb heat from the Sun in the same way? Or is there a difference? Perform the next activity and find out.
Activity 5 Which warms up faster? Objectives After performing this activity, you should be able to 1. 2. 3.
compare which warms up faster: sand or water compare which cools faster: sand or water use the results of the activity to explain sea breeze and land breeze
What to use 2 identical plastic containers 2 thermometers 2 iron stands with clamps string water sand
What to do 1.
In the shade, set up everything as shown below. The bulbs of the thermometer should be 2 cm below the surface of the water and sand.
247
Figure 13. Setup for Activity 5 2.
Wait for 5 minutes, then read the initial temperature of the water and sand. Record the temperature readings below. Initial temperature reading for water: __________ Initial temperature reading for sand: __________
3.
Now, place the setup under the Sun. Read the thermometers again and record the temperature readings in Table 1. Read every 5 minutes for 25 minutes. Table 1. In the Sun Observation time (minutes) 0 5 10 15 20 25
4.
Water
Sand
After 25 minutes, bring the setup back to the shade. Read the thermometers and record the temperature readings in Table 2. Read every 5 minutes for 25 minutes.
248
Table 2. In the shade Observation time (minutes) 0 5 10 15 20 25 5.
Water
Sand
Study the data in the tables and answer the following questions.
Q1. Which has a higher temperature after 25 minutes in the Sun, water or sand? Q2. After 25 minutes, how many Celsius degrees was the increase in the temperature of the water? Of the sand? 6.
Make a line graph using the temperature readings taken while the setup was in the Sun.
Q3. Based on the graph, which became hot faster, water or sand? Q4. What happened to the temperature of the water and sand when brought to the shade? Q5. How many Celsius degrees was the decrease in temperature of the water after 25 minutes? Of the sand? 7.
Make a line graph using the temperature readings taken when the setup was in the shade. Q6. Based on the graph, which cooled down faster, water or sand?
Sea Breeze and Land Breeze The sand and water in the previous activity stand for land and water in real life. From the activity, you have learned that sand heats up faster than water, and that sand cools down faster than water. In the same way, when land surfaces are exposed to the Sun during the day, they heat up faster than bodies of water. At night, when the Sun has set, the land loses heat faster than bodies of water. How does this affect the air in the surroundings? Imagine that you are standing by the sea, along the shore. During the day, the land heats up faster than the water in the sea. The air above land will then become warm ahead of the air above the sea. You know what happens to warm air: it rises. So the warmer air above the land will rise. The air above the sea will then move in to replace the rising warm air. (See drawing below.) You will then feel this moving air as a light wind—a sea breeze.
249
Figure 14. When does sea breeze occur? What will happen at night, when the Sun is gone? The land and sea will both cool down. But the land will lose heat faster than the water in the sea. In other words, the sea will stay warm longer. This time the air above the sea will be warmer than that above land. The warm air above the sea will then rise. Air from land will move out to replace the rising warm air. (See drawing below.) This moving air or wind from land is called a land breeze.
Figure 15. When does land breeze occur? In the illustration above, you can see an arrow pointing upward. This represents rising warm air. The place where warm air rises is a place where air pressure is low. In other words, the place where warm air is rising is a low-pressure area. In contrast, cold air is dense and tends to sink. The place where cold air is sinking is a high-pressure area. Based on what you learned so far, in what direction does air move, from a low-pressure area to a high-pressure area or the other way around? You probably know the answer already. But the next section will make it clearer for you.
Monsoons Do you know what monsoons are? Many people think that monsoons are rains. They are not. Monsoons are wind systems. But these winds usually bring abundant rainfall to the country and this is probably the reason why they have been mistaken for rains. In Filipino, the monsoons are called amihan or habagat, depending on where the winds come from. Find out which is which in the following activity. 250
Activity 6 In what direction do winds blow–from high to low pressure area or vice versa? Objectives After performing this activity, you should be able to 1. 2. 3. 4.
Interpret a map to determine direction of wind movement Explain why it is cold around in December to February and warm around July. Illustrate why habagat brings lots of rain Give examples how the monsoons (amihan and habagat) affect people.
What to use Figure 16: Pressure and Winds in January Figure 17: Pressure and Winds in July pencil
What to do Part I. Study Figure 16. It shows the air pressure and direction of winds in different parts of the world in January. Low-pressure areas are marked by L and high-pressure areas are marked by H. Broken lines with arrowheads show the direction of the wind. Q1. Choose a low-pressure area and study the direction of the winds around it. Do the winds move toward the low-pressure area or away from it? Q2. Choose a high-pressure area and study the direction of the winds around it. Do the winds move toward the high-pressure area or away from it? Q3. In what direction do winds blow? Do winds blow from high-pressure areas to low-pressure areas? Or, from low-pressure areas to high-pressure areas? Q4. Where is North in the map? South? West? East? Write the directions on the map. Q5. Where is the Philippines on the map? Encircle it. Q6. Study the wind direction near the Philippine area. From what direction does the wind blow near the Philippines in January?
251
252
Figure 16. Pressure and Winds in January
253
Figure 17. Pressure and Winds in July
Part II. Study Figure 18. It shows the air pressure and direction of winds in different parts of the world in July. Q7.
Study the wind direction near the Philippine area. From what direction does the wind blow in the vicinity of the Philippines in July?
Figure 16 shows what happens during the colder months. The wind blows from the high-pressure area in the Asian continent toward the low-pressure area south of the Philippines. The cold air that we experience from December to February is part of this wind system. This monsoon wind is locally known as amihan. As you can see from Figure 16, the wind passes over some bodies of water before it reaches the Philippines. The wind picks up moisture along the way and brings rain to the eastern part of the Philippines. Now, what happens during the warmer months? Study Figure 17 carefully. What do you observe about the low-pressure area and high-pressure area near the Philippines? They have changed places. (You will learn why in the next module.) As a result, the direction of the wind also changes. This time the wind will move from the high-pressure area in Australia to the low-pressure area in the Asian continent. This monsoon wind is locally called habagat. Trace the path of the habagat before it reaches the Philippines. Can you explain why the habagat brings so much rain? Which part of the Philippines does the habagat affect the most? The monsoons, habagat and amihan, affect people in different ways. Try to explain the following. Why do farmers welcome the monsoons? Why are fisherfolk not so happy about the monsoons? Why do energy providers appreciate the monsoons? Why are fishpen owners worried about the monsoons? How do the monsoons affect your own town? In the next section, you will apply the two concepts once more to explain another weather event.
254
The Intertropical Convergence Zone (ITCZ) Many people who listen to weather forecasts are confused about the intertropical convergence zone. But it is easy to understand it once you know that warm air rises, and air moves toward the place where warm air is rising. Take a look at the drawing below.
Figure 18. Sun’s rays at the equator and at a higher latitude Figure 18 shows the rays of the Sun at two different places at noon. Study the drawing carefully. Where would you observe the Sun directly above you? When you are at the equator? Or when you are at a higher latitude? As you can see, the position of the Sun at midday depends on where you are. At the equator, the Sun will be directly overhead and the rays of the Sun will hit the ground directly. At a higher latitude, the Sun will be lower in the sky and the Sun’s rays will strike the ground at a lower angle. Where do you think will it be warmer? It is clear that it is warmer at the equator than anywhere else. Because of that, the air over the equator will be warmer than the air over other parts of the Earth. And you already know what happens to warm air. It rises. And when warm air rises, air in the surroundings will then move as a result.
Figure 19. How does the air move at the equator?
255
As you can see from Figure 19, air from north of the equator and air from south of the equator will move toward the place where warm air is rising. Thus, the intertropical convergence zone is the place where winds in the tropics meet or converge. (Recall that the area near the equator is called the tropics.) In time the rising warm air will form clouds, which may lead to thunderstorms. Now you know why weather forecasters often blame the ITCZ for some heavy afternoon rains. The band of white clouds in the following picture shows the location of the ITCZ.
Figure 20. Satellite photo showing the location of ITCZ
Summary This module discussed global atmospheric phenomena like the greenhouse effect and global warming (including ozone depletion) that affect people, plants, animals and the physical environment around the world. And though the greenhouse effect is a natural phenomenon, there is a growing concern that human activities have emitted substances into the atmosphere that are causing changes in weather patterns at the local level. Highlighted in this module are concepts used to explain common atmospheric phenomena: why the wind blows, why monsoons occur, and what is the so-called inter tropical convergence zone. It is important for everyone to understand the varied atmospheric phenomena so that we can all prepare for whatever changes that occur in the environment and cope with these changes. There are still many things to learn about the atmosphere, specifically on weather and climate. You have just been provided with the basic concepts. You will learn more as you move to Grade 8 and onwards.
256
Suggested time allotment: 10 hours
Unit 4 MODULE
3
SEASONS AND ECLIPSES
Overview In Grade 6, you have learned about the major members of our solar system. Like the other planets, the Earth moves mainly in two ways: it spins on its axis and it goes around the Sun. And as the Earth revolves around the Sun, the Moon is also revolving around the Earth. Can you imagine all these “motions” happening at the same time? The amazing thing is we do not feel that the Earth is moving. In reality, the planet is speeding around the Sun at 30 kilometers each second. (The solar system is also moving around the center of the Milky Way!) But even if we do not actually see the Earth or Moon moving, we can observe the effects of their motion. For example, because the Earth rotates, we experience day and night. As the Moon goes around the Earth, we see changes in the Moon‘s appearance. In this module you will learn that the motions of the Earth and Moon have other effects. Read on and find out why.
Seasons In Grade 6, you tracked the weather for the whole school year. You found out that there are two seasons in the Philippines: rainy and dry. You might have noticed too that there are months of the year when it is cold and months when it is hot. The seasons follow each other regularly and you can tell in advance when it is going to be warm or cold and when it is going to be rainy or not. But can you explain why there are seasons at all? Do you know why the seasons change? The following activity will help you understand why.
257
Activity 1 Why do the seasons change? Objective After performing this activity, you should be able to give one reason why the seasons change.
What to use Figures 1 to 5
What to do 1.
Study Figure 1 carefully. It shows the Earth at different locations along its orbit around the Sun. Note that the axis of Earth is not perpendicular to its plane of orbit; it is tilted. The letter “N” refers to the North Pole while “S” refers to the South Pole.
Figure 1. The drawing shows the location of the Earth at different times of the year. Note that the axis of Earth is not vertical; it is tilted. (Not drawn to scale) Q1. In which month is the North Pole tilted toward the Sun– in June or December? Q2. In which month is the North Pole tilted away from the Sun– in June or December?
258
2.
Study Figure 2 carefully. The drawing shows how the Earth is oriented with respect to the Sun during the month of June.
Figure 2. Where do direct rays from the Sun fall in June? Q3. In June, which hemisphere receives direct rays from the Sun– the Northern Hemisphere or Southern Hemisphere? 3.
Study Figure 3 carefully. The drawing shows how the Earth is oriented with respect to the Sun during the month of December.
Figure 3. Where do direct rays from the Sun fall in December?
259
Q4. In December, which hemisphere receives direct rays from the Sun- the Northern Hemisphere or Southern Hemisphere?
Look at Figure 1 again. Note that the axis of the Earth is not perpendicular to the plane of its orbit; it is tilted from the vertical by 23.5 degrees. What is the effect of this tilt? In June, the North Pole is tilted toward the Sun. Naturally, the Northern Hemisphere will also be tilted toward the Sun. The Northern Hemisphere will then receive direct rays from the Sun (Fig. 2). When the Sun’s rays hit the ground directly, the place will become warmer than when the rays are oblique (Figures 4 and 5). This is why it is summer in the Northern Hemisphere at this time. But the Earth is not stationary. The Earth goes around the Sun. What happens when the Earth has moved to the other side of the Sun? After six months, in December, the North Pole will be pointing away from the Sun (Figure 1). The Northern Hemisphere will no longer receive direct rays from the Sun. The Northern Hemisphere will then experience a time of cold. For temperate countries in the Northern Hemisphere, it will be winter. In tropical Philippines, it is simply the cold season. What’s the angle got to do with it? “Direct rays” means that the rays of the Sun hit the ground at 90°. The rays are vertical or perpendicular to the ground. When the Sun’s rays strike the ground at a high angle, each square meter of the ground receives a greater amount of solar energy than when the rays are inclined. The result is greater warming. (See Figure 4.) On the other hand, when the Sun’s rays come in at an oblique angle, each square meter of the ground will receive a lesser amount of solar energy. That’s because at lower angles, solar energy will be distributed over a wider area. The place will then experience less heating up. (See Figure 5.) Figure 4. In the tropics, the warm season is due to the Sun’s rays hitting the ground directly. To an observer, the position of the Sun at noon will be exactly overhead.
260
Which part of the Earth receives the direct rays of the Sun in December? As you can see in Figure 3, it is the South Pole that is tilted toward the Sun. This time the Sun’s direct rays will fall on the Southern Hemisphere. It will then be summer in the Southern Hemisphere. Thus, when it is cold in the Northern Hemisphere, it is warm in the Southern Hemisphere. After another six months, in June of the following year, the Earth will have made one full trip around the Sun. The Sun’s direct rays will fall on the Northern Hemisphere once more. It will be warm in the Northern Hemisphere and cold in the Southern Hemisphere all over again. Thus, the seasons change because the direct rays of the Sun shift from one hemisphere to the other as the Earth goes around the Sun.
Figure 5. The cold season is the result of the Sun’s rays striking the ground at a lower angle. To an observer, the Sun at midday will not be directly above; it will be lower in the sky. Now you know one of the reasons why the seasons change. Sometimes the Sun’s direct rays fall on the Northern Hemisphere and sometimes they fall on the Southern Hemisphere. And that is because the Earth is tilted and it goes around the Sun. There is another reason why the seasons change. Find out in the next activity.
261
Activity 2 How does the length of daytime and nighttime affect the season? Objectives After performing this activity, you should be able to 1. Interpret data about sunrise and sunset to tell when daytime is long and when daytime is short; 2. Infer the effect of length of daytime and nighttime on seasons; 3. Summarize the reasons why seasons change based on Activity 1 and Activity
What to use Table 1
What to do 1.
Study the table below. It shows the times of sunrise and sunset on one day of each month. Table 1: Sunrise and sunset in Manila on selected days of 2011 Length of Day Sunrise Sunset daytime Jan 22, 2011 6:25 AM 5:50 PM 11h 25m Feb 22, 2011 6:17 AM 6:02 PM 11h 45m Mar 22, 2011 5:59 AM 6:07 PM 12h 08m Apr 22, 2011 5:38 AM 6:11 PM 12h 33m May 22, 2011 5:27 AM 6:19 PM 12h 52m Jun 22, 2011 5:28 AM 6:28 PM 13h 00m Jul 22, 2011 5:36 AM 6:28 PM 12h 52m Aug 22, 2011 5:43 AM 6:15 PM 12h 32m Sep 22, 2011 5:45 AM 5:53 PM 12h 08m Oct 22, 2011 5:49 AM 5:33 PM 11h 44m Nov 22, 2011 6:00 AM 5:24 PM 11h 24m Dec 22, 2011 6:16 AM 5:32 PM 11h 16m
Q1. Compare the times of sunrise from January, 2011 to December, 2011. What do you notice? Q2. Compare the times of sunset during the same period. What do you notice? Q3. Compare the time of sunrise on June 22, 2011 with that on December 22, 2011. On which day did the Sun rise earlier?
262
Q4. Compare the time of sunset on June 22, 2011 with that on December 22, 2011. On which day did the Sun set later? Q5. When was daytime the longest? Q6. When was daytime the shortest?
You know that there are 24 hours in a day. You probably think that daytime and nighttime are always equal. But you can infer from the activity that the length of daytime changes from month to month. When the North Pole is tilted toward the Sun, daytime will be longer than nighttime in the Northern Hemisphere. What happens when daytime is longer than nighttime? The time of heating up during the day will be longer than the time of cooling down at night. The Northern Hemisphere steadily warms up and the result is summer. At the same time, in the Southern Hemisphere, the opposite is happening. Nights are longer than daytime. It is winter there. But when the Earth has moved farther along its orbit, the North Pole will then be tilted away from the Sun. Nighttime will then be longer than daytime in the Northern Hemisphere. There would be a shorter time for heating up and longer time to cool down. The result is winter in the Northern Hemisphere. In tropical Philippines, it is the cold season. Meanwhile, it will be summer in the Southern Hemisphere. At this point, you should now be able to explain why the seasons change. Your explanation should include the following things: the tilt of the Earth; its revolution around the Sun; the direct rays of the Sun, and the length of daytime. There are other factors that affect the seasons but these are the most important. After discussing the motions of the Earth, let us now focus on the motions of another celestial object, the Moon. You have seen that the shape of the Moon appears to change from night to night. You have learned in Grade 5 that the changing phases of the Moon are due to the revolution of the Moon. The movement of the Moon also produces other phenomena which you will learn in the next section.
Shadows and Eclipses Do you know how shadows are formed? How about eclipses? Do you know why they occur? Do you think that shadows and eclipses are related in any way? In this section, you will review what you know about shadows and later on perform an activity on eclipses. Afterwards, you will look at some common beliefs about eclipses and figure out if they have any scientific bases at all.
263
Using a shadow-play activity, your teacher will demonstrate how shadows are formed and how shadows affect the surroundings. The demonstrations should lead you to the following ideas:
When a light source is blocked by an object, a shadow of that object is cast. The shadow will darken the object on which it falls. The distance of the object from the light source affects the size of its shadow. When an object is closer to the light source, its shadow will appear big. But when it is farther from the light source, its shadow is smaller. The occurrence of shadows is an ordinary phenomenon that you experience every day. Shadows can be seen anywhere. Sometimes, the shadow appears bigger than the original object, other times smaller.
How about in outer space? Are shadows formed there, too? How can you tell when you are here on Earth? The next activity will help you answer these questions. The materials that you will use in the activity represent some astronomical objects in space. You will need to simulate space by making the activity area dark. Cover the windows with dark materials such as black garbage bag or dark cloth.
Activity 3 Are there shadows in space? Objective After performing this activity, you should be able to explain how shadows are formed in space.
What to use
1 big ball (plastic or Styrofoam ball) 1 small ball (diameter must be about ¼ of the big ball) flashlight or other light source 2 pieces barbecue stick (about one ruler long) any white paper or cardboard larger than the big ball Styrofoam block or block of wood as a base
What to do Note: All throughout the activity, stay at the back or at the side of the flashlight as much as possible. None of your members should stay at the back of the big ball, unless specified.
264
1.
Pierce the small ball in the middle with the barbecue stick. Then push the stick into a Styrofoam block to make it stand (see drawing on the right). The small ball represents the Moon. Do the same to the big ball. The big ball represents the Earth.
2.
Hold the flashlight and shine it on the small ball (see drawing below). The distance between the flashlight and the ball is one footstep. Observe the small ball as you shine light on it. The flashlight represents the Sun. Sun
Moon
1 footstep Q1. What is formed on the other side of the Moon? 3.
Place the Earth one footstep away from the Moon (see drawing below). Make sure that the Sun, Moon, and Earth are along a straight line. Turn on the flashlight and observe. Moon
Sun
1 footstep
Earth
1 footstep
Q2. What is formed on the surface of the Earth? 4.
Place the white paper one footstep away from the Earth (see drawing below). The white paper must be facing the Earth. Observe what is formed on the white paper. Earth
Moon
Sun
1 footstep
1 footstep
Q3. What is formed on the white paper?
265
1 footstep
5.
Ask a group mate to move the Moon along a circular path as shown below.
Circular path Q4. What happens to the shadow of the Moon as you move the Moon around the Earth? Q5. Observe the appearance of the Moon. What is the effect of the shadow of the Earth on the Moon as the Moon reaches position X (see drawing above)?
You have just simulated the formation of shadows of astronomical objects in space. The formation and darkening is exactly the same as the formation of shadows commonly seen around you. When shadows are formed on astronomical objects, a darkening effect is observed. This phenomenon is called an eclipse.
How Do Eclipses Happen? In the earlier grades, you learned about the members of the solar system. You know that the Sun gives off light. As the different members of the solar system move around the Sun, they block the light from the Sun and form shadows. What this means is that planets have shadows, and even their moons have shadows, too. But we cannot see the shadows that they form because we are far from them. The only shadows that we can observe are the shadows of the Moon and Earth.
Figure 6. Look at the shadows of the Moon and Earth. Where does the shadow of the Moon fall? Where does the shadow of the Earth fall? 266
Look at Figure 6. (Note that the objects are not drawn to scale.) In the drawing, there are two Moons. Of course, you know that we only have one Moon. The figure is just showing you the Moon at two different locations as it goes around the Earth. The figure shows where the shadows of the Moon and Earth are as viewed in space. But here on Earth, you cannot observe these shadows. Why? Look at the shadow of the Moon in positions A and B. In position A, the Moon is too high; its shadow does not fall on Earth. In position B, the Moon is too low; the shadow of the Earth does not fall on the Moon. The shadows of the Earth and Moon are cast in space. So, when can we observe these shadows? In what positions can we see these shadows? Let us look at another arrangement.
Figure 7. When does the shadow of the Moon fall on Earth? When does Earth cast a shadow on the Moon? In Figure 7, the Earth has moved along its orbit, taking the Moon along. The Moon is shown in two different locations once more. Note that at these positions, the Moon is neither too high nor too low. In fact, the Moon is in a straight line between the Sun and the Earth. You can say that the three objects are perfectly aligned. At position A, where does the shadow of the Moon fall? As you can see, the shadow of the Moon now falls on the Earth. When you are within this shadow, you will experience a solar eclipse. A solar eclipse occurs when the Moon comes directly between the Sun and Earth (Figure 7, position A). You have simulated this solar eclipse in Activity 3.
Figure 8. Where is the Moon in relation to the Sun and Earth during a solar eclipse? 267
Let us look at the Sun, Moon, and Earth in Figure 8. Look at the tip of the shadow of the Moon as it falls on Earth. Is the entire shadow of the Moon completely dark? Do you notice the unequal shading of the shadow? Actually this unequal shading is comparable to what you have observed in your simulation activity. Remember the shadow of the small ball (Moon) on the big ball (Earth) in your activity? It has a gray outer part and a darker inner part (Figure 9). In the case of the Moon’s shadow, this gray outer region is the penumbra while the darker inner region is the umbra. If you are standing within the umbra of the Moon’s shadow, you will see the Sun disappear from your view. The surroundings appear like it is early evening. In this case, you are witnessing a total solar eclipse. In Figure 9. Is the shadow of the small ball comparison, if you are in the uniformly dark? penumbra, you will see the Sun partially covered by the Moon. There are no dramatic changes in the surroundings; there is no noticeable dimming of sunlight. In this case, you are observing a partial solar eclipse. Let us go back to Figure 7. Look at the Moon in position B. Do you notice that at this position the Moon is also aligned with the Sun and Earth? At this position, a different type of eclipse occurs. This time, the Moon is in the shadow of the Earth. In this case, you will observe a lunar eclipse. A lunar eclipse occurs when the Moon is directly on the opposite side of the Earth as the Sun. The occurrence of a lunar eclipse was simulated in the activity. Do you remember the small ball (Moon) in position X? You noticed that the shadow of the big ball (Earth) darkened the whole surface of the small ball. In a lunar eclipse, the shadow of the Earth also darkens the Moon (Figure 10).
Figure 10. Where is the Earth in relation to the Sun and Moon during a lunar eclipse? 268
Focus your attention on the shadow of the Earth in Figure 10. The shadow is wider than that of the Moon. It also has an umbra and a penumbra. Which part of the Earth’s shadow falls on the Moon? Is the Moon always found within the umbra? The appearance of the Moon is dependent on its location in the Earth’s shadow. When the entire Moon is within the umbra, it will look totally dark. At this time you will observe a total lunar eclipse. But when the Moon passes only through a part of the umbra, a partial lunar eclipse will be observed. A part of the Moon will look dark while the rest will be lighter. In earlier grades, you learned that it takes about one month for the Moon to complete its trip around the Earth. If that is the case, then we should be observing monthly eclipses. In reality, eclipses do not occur every month. There are only about three solar eclipses and three lunar eclipses in a year. What could be the reason for this? The answer lies in the orbit of the Moon. Look at the orbit of the Earth and the Moon in Figures 6 and 7. Do their orbits have the same orientations? As you can see the Moon’s orbit is slightly inclined. The orbit is tilted by 5 0 from the plane of the orbit of the Earth. As the moon moves around the Earth, it is sometimes higher or lower than the Earth. In these situations, the shadow of the Moon does not hit the surface of the Earth. Thus, no eclipses will occur. Eclipses only happen when the Moon aligns with the Sun and Earth.
Facts, Myths, and Superstitions Some people believe that a sudden darkening during the day (solar eclipse) brings bad luck. Others say that it is also bad luck when the Moon turns dark during a Full Moon (lunar eclipse). Do you think these beliefs regarding eclipses are true? Let us find that out in the next activity.
Activity 4 Does a Bakunawa cause eclipses? Objective When you finish this activity, you should be able to evaluate some beliefs about eclipses.
What to do 1. Collect some beliefs about eclipses. You may ask older people in your family or in the community or, you may read on some of these beliefs.
269
Table 2. Beliefs related to eclipses and its scientific bases Beliefs
Scientific explanations
Ancient Tagalogs call eclipses as laho. Others call it as eklepse (pronounced as written). Old people would tell you that during laho or eklepse, the Sun and the Moon are eaten by a big snake called Bakunawa. The only way to bring them back is to create a very loud noise. The Bakunawa gets irritated with the noise and spews out the Sun and the Moon back to the people.
Q1. Which beliefs and practices have scientific bases? Why do you say so? Q2. Which beliefs and practices have no scientific bases? Support your answer.
Which among the beliefs you have collected do you consider true? Do all the beliefs you have collected have scientific bases? Are the explanations of the occurrences of eclipses related to these beliefs? Are there any proofs that tell you they are true? In science, explanations are supported with evidence. Beliefs related to eclipses, such as the Sun being swallowed by Bakunawa (a large animal), or the increase of harmful microorganisms during an eclipse, are passed on by adults to young children. But until now, no proof has been offered to show that they are true. However, there are beliefs that have scientific bases. For example, it is bad to look directly at the Sun during a solar eclipse. Doing so will damage your eyes. This is true. Even if only a thin crescent of the Sun is left uncovered by the Moon, it will still be too bright for you to observe. In fact, it is 10,000 times brighter than the Full Moon and it will certainly harm your retina. So if you ever observe a solar eclipse, be ready with a solar filter or welder’s goggles to protect your eyes. Now you are an informed student on the occurrence of eclipses. The next time an eclipse occurs, your task is to explain to your family or the community the factors that cause eclipse.
Summary You may still be wondering why the topics Seasons and Eclipses were discussed together in a single module. The reason is that these phenomena are mainly the result of the motions of the Earth and Moon through space. As the Earth goes around the Sun, the northern and southern hemispheres are alternately exposed to the direct rays of the Sun, leading to the annual changes in seasons. And as the Moon goes around the Earth, it sometimes forms a straight line with the Sun and Earth, leading to the occurrence of eclipses. We do not directly see nor observe the motions of the Earth and Moon, but we can observe the phenomena that arise because of them.
270
