1. A red-hot horseshoe is placed on an anvil at room temperature. Which way does the heat flow? Explain. 2. How are refrigerators and heat engines related?

12. The temperature of a rapidly expanding gas decreases. Explain why in terms of the first law of thermodynamics. (Hint: Consider whether the gas does work and whether heat transfer occurs rapidly into the gas through conduction.)

2. As an example of microscopic thermodynamic analysis based on thermal-energy microstates, the figure to the right illustrates two systems (A and B), each containing two indistinguishable particles and possible energy levels from 1 to 8, with a particle residing in a given energy level having the same amount of energy as the level (e.g., a particle in energy-level 4 has 4 units of energy). The combined systems have a fixed total of 12 units of energy. Assuming that energy can be exchanged between the two systems, calculate the difference in entropy between condition #1 where the left-hand side has 8 units of energy and the right-hand side has 4 units of energy compared to condition #2 when the two sides reach their equilibrium condition. Note that the figure just shows one example of a configuration for condition #1. 8. 8 7 7 5 4 4 3 2 2 1 1

4. The first law of thermodynamics states that a. components of a system interact. b. entropy of a closed system always increases. c. closed system always shifts toward disorder or homogeneity. d. Energy is always conserved. 5. According to the second law of thermodynamics, the heat received from a high temperature reservoir by a heat engine operating in a complete cycle a. must be completely converted to work. b. equals the entropy increase. C. converted completely into internal energy. d. cannot be completely converted to work.