THERMODYNAMIC THERMODYNAMIC LAB: SPECIFIC HEAT OF METALS JULFAIZE BIN ONG KIM CHUAN @ AFFENDY BK16110167 GROUP 4 HK08 MECHANICAL ENGINEERING FACULTY OF ENGINEERING UNIVERISITY MALAYSIA SABAH
ABSTRACT The experiment is conducted to determine the specific heat of metal. The amount needed to increase the temperature by one degree Celsius per unit mass is called ‘The Specific Heat’. This experiment usually applied to metallic element to compare the energy absorbed and transferred by that particular metallic element. For t his experiment, the three metals samples will be heated to at least 70ºC then the temperature will be measured as initial temperature of the metal. Immediately the metal is transferred into a Styrofoam cup that contain water with lower temperature. The metal sample will be left for a few minutes for the metal and water to reach thermal equilibrium. Then, the temperature is taken as the final temperature. From this experiment, the specific heat we obtained are (0.232 cal. /g ºC), 0.1681 (cal. /g ºC) and 0.2685 (cal. /g ºC) for trial 1, trial 2, and trial 3, respectively for aluminum. Where the actual specific heat capacity is 0.21 (cal. /g ºC). In the calculation, we use the formula of Heat gained/lost, = ∆
TABLE OF CONTENT
No
Content
Page
1
Cover Page
1
2
Abstract
2
3
Table of content
3
4
Introduction
4
5
Procedure
4
6
Result
5
7
Discussion
6
8
Conclusion
6
9
Reference
6
10
Appendices
7-9
89K2K09N INTRODUCTION / OBJECTIVE Specific Heat is defined as he amounts of heat per unit mass required to raise the temperature by one degree Celsius. The relationship between heat and temperature change is usually expressed in the form = ∆ . However, this relationship does not apply if phase change occurs because heat added or removed during phase change does not change temperature. The specific heat of water is 1 calorie/gram °C = 4.186 joule/gram °C which is higher than any other common substance. As a result, water plays a very important role in temperature regulation. The specific heat per gram for water is much higher than that for a metal The main objective of this experiment is to determine the specific heat of metals and to compare them with the theoretical value given. In this experiment, the metal we choose is Aluminum which has theoretical value of 0.21 cal./g•°C. we use the equation = ∆
to calculate the specific heat of metal.
PROCEDURE 1.Three metals samples (Aluminum) was placed into a beaker of water and heated to at least 70º C. As little water as possible was used just enough to completely cover the three samples. The metal is immerged for a few minute to make sure equilibrium take place between metal and water. 2.A measured mass of cold tap water was poured into each of Styrofoam cups and the initial temperature of the water was measured. 3.The metal samples were quickly removed from the hot water and were placed into the separate Styrofoam cups of water. The initial temperature of the metal was measured by measuring the temperature of the water. A lid was placed on the cup and the water and the metal was left for a few minutes to achieve thermal equilibrium. The final temperature of the metal was measured. 4. The heat gained by the water was determined which is equal to the heat lost by t he metal. 5.With the information on the heat lost by metal, mass and temperature change, the specific heat of the metal was calculated. 6.The specific of the accepted value were observed and the percentage errors were calculated.
RESULT TRIAL 1
2
3
Al
Al
Al
192.2514
177.225
167.9141
27.5ºC
27ºC
27ºC
17.6000
17.4897
16.7356
Initial temp. of metal (ºC)
75ºC
76ºC
73.5 ºC
Final temp. of metal and cold water (ºC)
28 ºC
27.8 ºC
28.2 ºC
Change in temp. Of water (ºC)
1 ºC
0.8 ºC
1.2 ºC
Heat gained by water (cal.)
192.2514
141.78
201.4976
Heat lost by metal=_heat gained by water (cal.)
-192.2514
-141.78
-201.4976
47 ºC
48.2 ºC
45.3 ºC
EXPERIMENTAL specific heat of metal (cal./ g ºC)
0.232 (cal./ g ºC)
0.1681 (cal./ g ºC)
0.2658 (cal./ g ºC)
ACCEPTED specific heat of metal (cal./ g ºC)
0.21 (cal./ g ºC)
0.21 (cal./ g ºC)
0.21 (cal./ g ºC)
10.67%
19.9%
26.56%
Name of metal Mass of cold water (g) Initial temp. of cold water (ºC) Mass of metal (g)
Change in temp. Of metal (ºC)
Percent error
DISCUSSION For this experiment, three aluminium metal cylinders are used to identify its specific heat of metal. After the experiment, the specific heat we obtained are (0.232 cal. /g ºC), 0.1681 (cal. /g ºC) and 0.2685 (cal. /g ºC) for trial 1, trial 2, and trial 3, respectively. The percentage error in order to obtain the result were 11%, 20% and 27% for each respective trial. This percentage error may be due to several reasons such as:(i) The heat from the hot water lose to it surrounding before it can reach equilibrium with the metal. Hence, initial temperature of metal may be changed. We need to make sure to immediately immersed the metal into the cold water. (ii) The time taken for the metal and hot water t o reach equilibrium may vary with the volume of hot water. Since it is not fixed, we need to take longer time for it to really be in equilibrium state before taking the initial temperature. (iii) The composition of the three aluminium metals are unknown (whether it is 100% pure aluminium), hence the specific heat is not precise. Pure metal should be use when conducting the experiment. (iv) The heat from metal lose to it surrounding when it is immerged into cold water. Therefore, the final temperature of the metal is affected. We need to submerge the metal into cold water in a closed system.
CONCLUSION In conclusion, the specific heat we obtained are (0.232 cal. /g ºC), 0.1681 (cal. /g ºC) and 0.2685 (cal. /g ºC) for trial 1, trial 2, and trial 3, respectively. Where the actual specific heat capacity for Aluminum is 0.21 (cal. /g ºC). The percentage error in order to obtain the result were 11%, 20% and 27% for each respective trial. Despite of having slight differences between the actual and theoretical value of specific heat, this experiment is considered success by using the metal rod reached thermal equilibrium with hot water transferred to the cold water method.
REFERENCE 1.
Yunus A. Cengel, Michaele A.Boles, Thermodynamics 5 th Edition, Istanbul 2012
2.
Cap, A. (2006) Determining heat capacity of unknown metals. Retrieved from: https://adamcap.com/schoolwork/determining-the-heat-capacity-of-unknown-metals/
3.
Daniel V.Schroeder, “An Introduction to T hermal Physics.” (Addison-Wesley,2004) Foley Robert, “Specific Heat Capacity.” University of Wiscinson, 2006. Online at http://physics.uwstout.edu/univphys1/labs/specific.htm
4.
Definition of Specific Heat http://hyperphysics.phyastr.gsu.edu/hbase/thermo/spht.html
5.
Helmenstine, P. A. (n.d.). Here's How You Define Specific Heat Capacity. Retrieved October 12, 2017, https://www.thoughtco.com/definition-of-specific-heat-capacity605672
APPENDICES Calculation : % error =
−
× 100
Experimental Specific heat of metal =
×∆
Heat gained/lost, ; CH2O = 1 cal/g•°C
1st Trial
2nd Trial
3rd Trial
Heat gained/lost:
Heat gained/lost
Heat gained/lost
= ∆
= ∆
= ∆
=(192.2514)(1Cal/gºC)(1ºC)
=(177.225g)(1Cal/gºC)(1ºC)
=(167.9741g)(1Cal/gºC)(1ºC)
=192.2514 Cal
=141.7800 Cal
=201.4976 Cal
Experimental specific heat:
Experimental specific heat:
Experimental specific heat:
=
×∆
−92.254
=
(7.6)()
= 0.232 Cal/gºC
= =
×∆ −4.78
(7.4897)(.8)
= 0.1681 Cal/gºC
= =
×∆ −67.94 (6.7356)(.2)
= 0.2658 Cal/gºC
Percentage of error: =
−
.2−.232
=
.2
× 100
=10.67%
Percentage of error: × 100
=
−
.2−.68
=
.2
=19.9%
× 100
Percentage of error: × 100
= =
− .2−.2658 .2
=26.56%
× 100
× 100
Figure:
Figure 1 : Apparatus
Figure 2 : show the metal submerged in cold water
Figure 3 : Cup uses to place cold water.
Figure 3 : use to measure mass
Figure 4 : Thermometer and Beaker containing Hot water and metal
