Heat flows into a gas in a piston and the gas performs some work on its surroundings. The amount of work done is less than the heat added. In this situation,
A) the internal energy of the gas decreased.
B) the internal energy of the gas increased.
C) the internal energy of the gas did not change.
D) the gas experienced a phase change.
E) energy is not conserved and so it cannot happen.

Question

Quizplus · Accepted Answer

The internal energy of the gas increased because the heat added to the system is greater than the work done by the gas. According to the first law of thermodynamics, the change in internal energy is equal to the heat added to the system minus the work done by the system. If the work done is less than the heat added, the difference results in an increase in internal energy.

Heat Flows into a Gas in a Piston and the Gas