PASCO ET-8499 Energy Transfer Calorimeter - Manual (Page 15)

Model No. ET-8499 Experiment 2: Entropy
13 ®
Analysis Part A: Energy
1. Calculate the change in temperature,
∆
T, of the cup and cold water.
2. Calculate the change in temperature of the hot water.
3. Calculate the total amount of heat, Q
gained
, added to the cup and cold water. Use the proper
specific heat for each.
4. Calculate the total amount of heat, Q
lost
, given up by the hot water.
5. What percentage of the energy supplied by the hot water is delivered to the cold water and the
cup? Calculate the percent difference.
6. If you were very careful, this percentage should be down close to 1 or 2 percent. If not, check
for mistakes. If your percentage is over 5 percent, repeat the experiment before going on to
part B.
Analysys Part B: Entropy
1. Use equation (3) to calculate the change in entropy of the cup and cold water. Remember to
use Kelvin for the temperatures. Pay careful attention to which is the initial and which is the
final temperature: It affects the sign of your answer.
2. Use equation (3) to calculate the change in entropy of the hot water. Remember to use Kelvin
for the temperatures. Pay careful attention to which is the initial and which is the final
temperature: It affects the sign of your answer.
3. Calculate the total change in entropy of the system.
Questions
1. Evaluate the sign of the change in entropy for both parts of the system. Explain in terms of
"disorder" and the definition of entropy.
2. Evaluate the sign of the change in entropy for the entire system. Explain in terms of the
definition of entropy, and the concept of spontaneous processes.
3. When calculating heat flow (as in part A) it is not necessary to change the temperatures to
Kelvin, but when calculating entropy (as in part B) it is necessary. Explain why this is true.
% difference
Q
lost
Q
gained
–
Q
lost
------------------------------------ X 100(%) =