Unit 5: Thermodynamics and Kinetics

Answer: D — The correct answer, B, is true because when a gas is heated at constant volume, the energy transferred to the system as heat increases the internal energy of the system, which in turn increases the temperature of the gas. Option A is incorrect because heating the gas at constant volume would increase, not decrease, the temperature. Option C is incorrect because the process is not isothermal; the temperature of the gas increases. Option D is incorrect because the internal energy of the system increases, not decreases, and no work is done on or by the system in a constant-volume process.

Answer: B — The correct answer is B because the internal energy of an ideal gas is directly proportional to its temperature. As the temperature of the gas increases, the internal energy of the gas also increases. Option A is incorrect because the volume of the gas is constant, so there is no expansion. Option C is incorrect because the process is not isothermal (the temperature is changing). Option D is incorrect because the gas is being heated, not losing heat to the surroundings.

Answer: A — The correct answer is A because as the coffee loses heat to the surroundings, its entropy decreases. This is in accordance with the second law of thermodynamics, which states that in an isolated system, entropy will always increase over time. However, in this case, the system (coffee) is not isolated, and heat is being transferred from the coffee to the surroundings, resulting in a decrease in entropy of the coffee. The other options are incorrect because entropy is related to the disorder or randomness of a system, and as the coffee loses heat, its molecules move less, resulting in a more ordered state, or decreased entropy.

Answer: A — The correct answer is A because the internal energy of an ideal gas is a function of temperature only. As the temperature of the gas increases, the internal energy also increases. Option B is incorrect because the internal energy of an ideal gas does not depend on the work done by or on the system. Option C is incorrect because the internal energy can change even if the volume of the system does not change, as long as the temperature changes. Option D is incorrect because work is not required for the internal energy to increase; an increase in temperature is sufficient.

Answer: B — The correct answer is B because in an isothermal expansion, the entropy of an ideal gas increases due to the increased number of available microstates as the gas expands into a larger volume. Option A is incorrect because the expansion of the gas into a larger volume actually increases the entropy. Option C is incorrect because the isothermal process does allow for an increase in entropy due to the change in volume. Option D is incorrect because the temperature of the gas remains constant during the isothermal expansion.