Questions:
1. How much energy is gained by the ice as it melts to water?
2. How much energy does the environment reject?
3. By how much does the ice's entropy increase?
4. By how much does the environment's entropy decrease?
5. Due to exclusively this process, what was the net change in entropy of the entire universe?
Now suppose we take that now melted water hiking in the mountains, to an environment of Tc = 250 K. The water completely freezes, and we stop considering the process once it finishes freezing (i.e. we don't consider the subcooling of the ice).
Questions:
6. How much energy is lost by the water as it freezes to ice?
7. How much energy does the environment absorb?
8. By how much does the ice's entropy decrease?
9. By how much does the environment's entropy increase?
10. Due to exclusively this process, what was the net change in entropy of the entire universe?
Answers as formulas:
Melting
1. hf, gained
2. hf, lost
3. hf/Tm, increase
4. hf/Tbg, decrease
5. hf/Tm - hf/Tbg, net increase
Freezing
6. hf, lost
7. hf, gained
8. hf/Tm, decrease
9. hf/Tc, increase
10. hf/Tc - hf/Tm, net increase
Numeric answers:
Melting
1. 333 kJ gained
2. 333 kJ, lost
3. 1.22 kJ/K increase
4. 1.11 kJ/K decrease
5. +0.109 kJ/K net increase
Freezing
6. 333 kJ lost
7. 333 kJ gained
8. 1.22 kJ/K, decrease
9. 1.33 kJ/K increase
10. 0.113 kJ/K, net increase