SAT Subject Physics Practice Question 657: Answer and Explanation
8. Two separate 10L containers each contain a different gas. One gas is at a temperature of 400K; the other gas is at a temperature of 200K. When both gases are added to the same 10L container, which statement is correct?
I. The hotter gas loses heat to the cooler gas.
II. The hotter gas increases in temperature when the two are squeezed together.
III. The cooler gas decreases in temperature when placed into the second container.
A. I only
B. II only
C. I and III only
D. II and III only
E. I, II, and III
Correct Answer: A
The correct answer is (A). The first law of thermodynamics makes it clear that a hot object loses heat to a cold object. If no heat is added or subtracted from a system, the heat in the system remains constant in the system.