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Copper and water entropy

Page history last edited by Joe Redish 5 years, 3 months ago

7.3.2.P6

 

A 200 g block of copper at a temperature of 55oC is put into an insulated beaker containing 200 g water at 20oC. The specific heat of water is about 1.0 J/g-oC while the specific heat of copper is only about 0.4 J/g-oC. As a result, the two come to thermal equilibrium at a temperature of about 30 oC – much closer to the original temperature of the water than of the copper. 

 

1. From this you can conclude:

  1. There are more degrees of freedom in 200 g of copper than in 200 g of water.
  2. There are fewer degrees of freedom in 200 g of copper than in 200 g of water.
  3. There are about the same number of degrees of freedom in 200 g of copper as there are in 200 g of water.
  4. The information given doesn't tell you anything about the number of degrees of freedom in the matter. 
 		  

2. From this you can conclude that after the system has come to thermal equilibrium (choose all that apply):

  1. The average kinetic energy of one molecule of water is greater than that of one copper atom.
  2. The average kinetic energy of one molecule of water is less than that of one copper atom.
  3. The average kinetic energy of one molecule of water is the same as that of one copper atom.
  4. The information given doesn't tell you anything about the kinetic energy of the molecules/atoms.

 

3. Complete each sentence with I (increases), S (stays the same), D (decreases), or N (you can’t tell) 

  1. As the copper cools off, its entropy ___
  2. As the water warms up, its entropy ___
  3. As the two substances in the isolated water-copper system come into thermal equilibrium, their total entropy ___ 

 

4. Select statements that correctly describe how the energy of the copper block behaves during the process. 

  1. The internal energy of the copper block decreases until it reached thermal equilibrium, and then stops changing.
  2. The internal energy of the copper block fluctuates until it reaches thermal equilibrium, when the fluctuations stop.
  3. The internal energy of the copper block fluctuates throughout the experiment.
  4. The internal energy of the copper block did not change in the course of the experiment.

 

 

 

5/3/18 Bill Dorland & Joe Redish

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