Problem Five:

"What is the change in entropy in the following processes: (a) 1 kg of water at 100 ºC changes to steam at 100 ºC and at constant pressure; (b) 1 kg of ice at 0 ºC is converted to water at 0 ºC; (c) 1 kg of water at 0 ºC is heated to 100 ºC."

(a) At the assumed 1 atm, J/K.

(b) J/K

(c) From Chapter 19 on heat capacity and specific heat, we know that .

Therefore, .

So, .

In this case we have: J/K.

Problem Six:

"A 50-g ice cube at 0 ºC melts (reversibly) to water at 0 ºC. What is the change in entropy (a) of the ice; and (b) of the universe?"

(a) .05 kg(334)

J/K. Because the heat is transferred from the environment to the ice cube, the entropy of the ice must be negative, J/K.

(b) Entropy of the universe is J/K.