SAT Subject Physics Practice Question 498: Answer and Explanation
14. Two gases are insulated from their surroundings but are in contact with each other so heat can flow between them. One gas is hot at t = 0 and the other gas is cold at t = 0. After time passes and the gases equilibrate, which of the following will have happened?
A. The particles in the cold gas will have slowed in their rate of movement.
B. The particles in the hot gas will have increased their rate of movement.
C. The temperature of the cold gas will have decreased.
D. The temperature of the hot gas will have increased.
E. The temperature of the hot gas will have decreased.
Correct Answer: E
The correct answer is (E). The hot gas, which is in contact with the cold gas, will lose heat to the cold gas. The transfer of heat is always from the hot object to the cold object, unless work is done on the system.