EXAMPLE 1 (SPM 2012 – Paper3/Question 3)
Ethanol, propanol, butanol, water, [metal]
Diagram 1 shows spirit lamps that contain different types of alcohols.
Apparatus Copper container, spirit lamp, thermometer, electronic balance, wooden block, tripod stand, wind shield and measuring cylinder. [3 marks] f.
Procedure of the experiment
Diagram 1 Different types of alcohols produce different heat of combustions. When the number of carbon per molecule of the alcohol increases the heat of combustion increases. Table 1 shows the heat of combustion of ethanol, propanol and butanol.
1. 250 cm3 of water is poured into a copper container as shown in the diagram above. 2. Initial temperature of the water is recorded. 3. A spirit lamp is half filled with ethanol. 4. Initial mass of the spirit lamp is recorded. 5. The spirit lamp under the copper beaker and ignite the wick immediately. immediately. 6. Stir the water and the flame is put off after the temperature has increased by 30°C. 7. The highest temperature of the water is recorded 8. Immediately the final mass of the spirit lamp is recorded. 9. Repeat the experiment by replacing ethanol with propanol and butanol.
Table 1 Plan an experiment to compare the heat combustion of the alcohols. Your planning should include the following aspects: a.
Aim:
To determine the heat of combustion of various alcohol [2 marks] b.
Statement of the problem
How does the number of carbon per molecule of alcohol affect the heat of combustion? [2 marks] c.
All the variables
Manipulated variable: Types of alcohols Responding variable: Heat of combustion Fixed variable: Volume of water, type of container, size of container and spirit lamp
[3 marks] g.
Tabulating data
[3 marks] d.
Statement of the hypothesis
When the number of carbon per molecule of alcohol increases, the heat of combustion increases. [3 marks]
e.
List of substance/materials and apparatus
Substance/materials
[3 marks]
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EXAMPLE 2 (SPM 2012 – Paper3/Question 3)
Substances
Diagram 2 shows two methods of dissolving sugar cubes to make sugar solution.
Sodium thiosulphate solution solution 0.5 mol dm-3, sulphuric acid 1.0 mol dm -3 Apparatus Conical flask 250 cm3, measuring cylinder, thermometer, thermometer, Bunsen burner, filter paper, tripod stand, wire gauze, stopwatch e.
Procedure
Diagram 2 A group of students discovered that it is faster to dissolve the sugar cubes to make sugar solution by using hot water rather than cold water. This is due to the difference in the temperature of the water. Referring to the situation above, plan a laboratory experiment to investigate the effect of temperature on the rate of reaction between sulphuric acid and sodium thiosulphate solution .
3
1) 50 cm of sodium thiosulphate solution is poured into a conical flask. 2) The temperature of the solution is recorded. 3) The conical flask is placed on top of a piece of white paper with a mark ‘X’ at the centre. 4) 5 cm3 of sulphuric acid is added into the conical flask and the stopwatch is started immediately. 5) Swirl the conical flask and record the time taken for the mark ‘X’ to disappear from sight. 6) Repeat steps 1 to 5 by heating the sodium thiosulphate solution at temperatures of 40°C, 50°C and 60°C
Your planning should include the following aspects. a.
Statement of the problem
How does temperature effect the rate of reaction between sulphuric acid and sodium thiosulphate solution? b.
All the variables
Manipulated variable Temperature of sodium thiosulphate solution Responding variable Time taken for the mark ‘X’ to
disappear from
sight
Constant variable Volume and concentration of sulphuric acid/ sodium thiosulphate solution// volume of conical flask. c.
Statement of the hypothesis
f.
Tabulation of data
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Methanol is added to butanoic acid. The mixture is stirred. Several drops of concentrated sulphuric acid are added into the mixture using dropper. The mixture is warmed/heated. The scent produced is recorded. Repeat steps 1 to 5 using ethanol to replace methanol.
The fruits in Figure 2 produce natural esters which have various tastes and scents.
e.
Tabulation of data
Figure 2 Esters can be produced in the laboratory when an alcohol reacts with a carboxylic acid. Table 2 shows types of alcohol and carboxylic acid used to produce various esters. These esters have a similar scent to the esters in fruits.
Table 2 You are required to prepare two different types of ester using the same carboxylic acid with different alcohols. The two esters must be chosen from those shown in Table 2. Use the information in Table 2 to plan a laboratory experiment to prepare the esters and describe their scents. Your explanation should include all the followings: a.
Aim of the experiment
Producing two esters using the same carboxylic acid and describe its scents.
b.
Statement of hypothesis
Different alcohol produces ester with different scents. c.
List of substances and apparatus
Butanoic acid, ethanol, methanol, concentrated sulphuric acid/Ethanoic acid, octanol, pentanol, concentrated sulphuric acid. Apparatus:
[17 marks]
