Specific Heat Capacity and Latent Heat Lab Report PDF

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Summary

Lab reprot for FY003 - Core Science.
Lab experiments for specific heat capacity of a material and latent heat of fusion of material.
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Description

Table of Contents International System of Units................................................................................................................ii Abbreviations........................................................................................................................................iii List of Figures........................................................................................................................................iv List of Tables..........................................................................................................................................v List of Graphs........................................................................................................................................vi List of Equations...................................................................................................................................vii 1.

Introduction...................................................................................................................................1

2.

Theory...........................................................................................................................................1

3.

Risk Assessment.............................................................................................................................1

4.

Method..........................................................................................................................................2

5.

Tables.............................................................................................................................................3

6.

Figures...........................................................................................................................................4

7.

Graphs...........................................................................................................................................4

8.

Calculations...................................................................................................................................5

9.

Conclusions....................................................................................................................................6

10.

References.................................................................................................................................6

11.

Appendices................................................................................................................................6

i

International System of Units Quantity Mass Time Temperature Energy Specific heat capacity Latent heat of fusion Volume

ii

Unit kilogram Seconds Degrees Celsius Joules Joules per kilogram per kelvin Joules per kilogram millilitres

Symbol Kg S or sec °C J

Jkg−1 K −1 −1 Jkg ml

Abbreviations Temp Lab L C E ΔΘ

iii

Temperature Laboratory Latent heat of fusion Specific heat capacity Energy Change in temperature

List of Figures Figure 5-1 Weighing scale…………………………………………………………………………………………..…………………….4 Figure 5-2 metal cylinder submerged in boiling water………………………………………………………………………4 Figure 5-3 metal cylinder eating the water in the beaker…………………………………………………….……………4 Figure 5-4 box of ice…………………………………………………………………………………………………..…………………….4 Figure 5-5 thermometer being used to measure temperature of water……………………………………………4

iv

List of Tables Table 4-1 Data needed to calculate Specific Heat Capacity……………………………..……………………..…………3 Table 4-2 Temp change of water heated by metal cylinder…………………..………………………..…………………3 Table 4-3 Data needed to calculate Latent Heat of Fusion………...………………………………………………………3 Table 4-4 Temp change of water cooled by ice…………………………………………………………………………….……3

v

List of Graphs Graph 6-1 Temperature change of water when the hot metal cylinder is submerged………………..……..4 Graph 6-2 Temperature change when ice is added to water…………………………………………….……………….4

vi

List of Equations 8-1……………………………………………………………………………………………………………………………………………………..5 8-2……………………………………………………………………………………………………………………………………………………..5 9-1……………………………………………………………………………………………………………………………………………………..6

vii

1. Introduction The experiment observes the energy transfer when there is a temperature imbalance. Between two substances. The experiment investigates the relationship between the energy required to change the temperature of a material and it’s mass. The aim of the experiment is to obtain a value for latent heat of fusion of water and the specific heat capacity of an unknown metal, then compare this with real values for various metals and make a judgment on what type of metal the cylinder is most likely made out of.

2. Theory The specific heat capacity of a material is the amount of energy per needed to raise the temperature of 1Kg of mass by 1 Kelvin. E=mC ΔΘ [1]. Heat is transferred when there is a temperature unbalance, in this experiment it is a hot metal cylinder at 100°C being submerged in water that is at room temperature. The metal transfers heat to the water, the water temp rises and the metal temp falls until they are equal. The energy lost by the metal is equal to the energy gained by the water (in practice some energy is lost to the environment). mmCm ΔΘm = mwCw ΔΘw

Hot

Energy transfer

Cold

Latent heat of fusion is the energy needed to change a unit of mass from a solid to a liquid while keeping the same temperature. E=mL [2]. Energy is transferred to ice for it to change state from a solid to a liquid. The energy needed = mL, assuming there is no temperature change. When the ice is added to the water there is energy transferred from the water to the ice. The energy lost by the water is equal to the energy needed to change the state of the ice and then raise its temperature. mwCw ΔΘw = miL + miCw ΔΘi

Cold

Energy transfer

Hot

3. Risk Assessment The metal cylinder is heated in boiling water, it has a piece of string tied to it so that it can be moved from the kettle to the beaker without skin coming into contact with the hot surface which would cause burns. Using the thermometers to measure the temp of the boiling water would lead to them exploding as the boiling water would be off the scale. Not only could the liquid inside cause irritation to skin but sharp glass could cut skin.

1

Glass beakers are used in the experiment, if dropped it will shatter, any glass should not be handled with bare hands and must be disposed of to prevent anyone else touching it. In the lab there is electronic equipment, be sure that there are no trailing wires which could cause a tripping hazard. Additionally the experiment should be set up away from any electronic equipment to prevent damage if there was a water spillage.

4. Method The method for obtaining data to calculate specific heat capacity of the metal was as follows: Weigh the metal cylinder on the top loading balance, ensuring it was zeroed first. Then suspend the weight from the clamp so that it is submerged in the boiling water [see figure 6-2], being sure not to make contact with the heating element in the kettle. If the metal cylinder was to touch the heating element it would cause a short circuit, current would not flow through the heating element therefore the water would cool down. Whilst the cylinder heated up, the 100ml beaker was weighed to obtain a value for its mass, this is necessary for the calculations [see figure 6-1]. Then the beaker was filled with 80ml of cold water and weighed again. A thermometer is used to measure the start temp of the water [see figure 6-5]. After at least 3 minutes it is assumed that the metal cylinder had reached 100°C. It was removed from the kettle, blotted on a tissue to remove water, and then placed in the cold water in the beaker [see figure 6-3]. At this point the water began to increase in temperature, readings were taken at 10 second intervals until the temperature stopped increasing, meaning that the water and metal cylinder were at thermal equilibrium. This process was then repeated to obtain a second set of results [see table 5-2]. The method for the second part, finding a value for Latent Heat of Fusion of ice was as follows: A Top loading balance was used to obtain a value for the mass of the beaker before and after 60ml of cold water was added. A reading was taken for the initial temp of the water, then a spoonful of ice was added [see figure 6-4]. The beaker, now containing water and ice, was weighed again, the total mass can was used to obtain a value for the mass of ice which was added. The temp of the water is measured at 10 second intervals until it stops falling, this meant that the ice had melted and the water was in thermal equilibrium. The process was then repeated to get a second set of data [see table 5-4].

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5. Tables Table 5-1 Data needed to calculate Specific Heat Capacity 1

2

Average

Beaker Weight empty/kg

0.0167

0.0167

0.0167

Beaker + Water Weight/kg

0.0965

0.0923

0.0944

Water weight/kg

0.0798

0.0756

0.0777

cylinder weight/kg Water start temp/°C Water max temp/°C

0.0525

0.0525

0.0525

23.0

23.0

23.0

31.5

32

31.8

Change in temp/°C

8.5

9.0

8.75

Table 5-3 Data needed to calculate Latent Heat of Fusion 1 2 Average Empty beaker weight/kg

0.0167

Beaker + Water Weight/kg

0.0749

0.0669

0.0709

0.0582

0.0502

0.0515

0.0794

0.0796

0.0795

0.0045

0.0127

0.0086

Start temp/°C

24.0

18.5

21.25

End temp/°C

17.0

8.0

12.5

Change in temp/°C

7.0

10.5

8.75

Water weight/kg Beaker, Water and ice Weight/kg Ice weight/kg

3

0.0167

Table 5-2 temp change of water heated by metal cylinder

Time/ seconds 0 10 20 30 40 50 60 70

1st results

2nd results

Temp/°C 23.0 27.0 28.0 29.5 30.0 31.0 31.5 End

Temp/°C 23.0 25.0 28.0 30.0 31.5 32.0 32.0 End

Table 5-4 Temp change of water cooled by ice

0.0167 Time/ seconds 0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0

1st results

2nd results

Temp/°C 24.0 18.0 17.3 16.5 16.8 17.0 17.0

Temp/°C 18.5 16.0 11.5 10.0 9.5 9.0 8.5 8.0 7.5 8.0

6. Figures

Figure 6-1 Top loading balance

Figure 6-2 Metal cylinder Figure 6-3 Metal cylinder eating submerged in boiling water the water in the beaker

Figure 6-4 Insulated box containing the ice

Figure 6-5 Thermometer being used to measure temperature of water

7. Graphs 34.0 32.0

28.0

Temp/°C

Temp/°C

30.0

26.0 24.0 22.0 20.0 0

10

20

30

40

50

60

70

Time/ s

Graph 7-1 Temperature change of water when the hot metal cylinder is submerged

4

25 23 21 19 17 15 13 11 9 7 5 0 10 20 30 40 50 60 70 80 90 100 Time/ s

Graph 7-2 Temperature change when ice is added to water

8. Calculations E=mC ΔΘ

8-1

Where: E = energy m = Mass C = specific heat capacity ΔΘ = Change in Temp Heat lost by metal = heat gained by water Heat lost by metal = mmCm ΔΘm = 0.0525 x C x (100 −31.8) = 3.58Cm Heat gained by water = mwCw ΔΘw = 0.0777 x 4182 x (31.8 −23 ) = 2859.5 Cmetal =

2859.5 3.58

= 798.7

−1

Jkg K

−1

C = 798.7 Jkg−1 K −1

E=mL

8-2

Where: E = energy m = Mass L = Latent heat of fusion Heat lost by water = Heat gained by ice Heat lost by water = mwCw ΔΘw = 0.0515 x 4182 x (21.25-12.5) = 1884.5 Heat gained by ice = miCw ΔΘi + miL = 0.0086 x 4182 x (12.5-0) + 0.0086 x L = 449.6 +0.0086 x L Therefore: 1884.5 = 449.6 + 0.0086 x L L=

1884.5 −449.6 0.0086

L = 1.67 x 105

5

= 166848.8 Jkg−1

Jkg−1

9. Conclusions The experiment has shown that the calculated value for C of the metal cylinder is 798.7 −1 −1 , using this value it can be speculated that the type of metal is aluminium, which has a Jkg K value of C = 930 Jkg−1 K −1 . The second part of the experiment shows that the Latent Heat of −1 Fusion is 1.67 x 105 , so 1.67 x 105 Joules of energy is needed to change the state of Jkg 1kg ice into water without raising the temperature. Errors during the experiment lead to results that deviate from the actual values for C and L. For the calculation of C the assumption was made that the start temp of the metal was 100°C because it heated by boiling water. No measurements were taken for the true temp of the water therefore giving an incorrect value for ΔΘ of the metal. The metal cylinder will also have lost heat to the environment during transfer from the kettle to the beaker in the form of convection, radiation, conduction. Heat was also lost when the water was dried off with a towel. Another cause of errors is that not all the energy lost by the metal is used to heat the water, energy also heats the beaker and lost in evaporation. To obtain more accurate results an insulated beaker should have been used. For the calculation of L it was assumed that the start temp of the ice was 0°C, It is likely that the ice was below 0°C, this will have lead to a false value for ΔΘ. The ambient room temperature was not taken into account. It would have transferred energy to the ice to melt it and raise the temperature. These errors in the experiment will lead to results which are different from the actual values. This is the percentage error. It can be calculated with the following formulae:

expected −actual expected

% error =

x100

9-1

Jkg−1 K −1 , the result that was obtained is 798.7 930−798.7 . Therefore the percentage error = x 100 = 14.1% 930

The specific heat capacity of aluminium is 930

Jkg−1 K −1

−1 Jkg , the result obtained is 1.67 x 10 3.282 x 105 −1.67 x 105 . Therefore the percentage error = x 100 = 49.1% 3.282 x 105

The latent heat of fusion of ice is 3.282 x 105

Jkg−1

5

10. References [1]. http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/spht.html [12/10/16] [2]. http://www.syvum.com/cgi/online/serve.cgi/squizzes/physics/latent_heat.html [12/10/16] [3].

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11. Appendices

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