During a slow adiabatic expansion of a gas:
A)the pressure remains constant
B)energy is added as heat
C)work is done on the gas
D)no energy enters or leaves as heat
E)the temperature is constant

Question

Quizplus · Accepted Answer

An adiabatic expansion means that no heat is added or removed from the system, so choice D is true. As the gas expands, work is done by the gas on its surroundings, so choice C is also true. However, since no heat is added or removed, the temperature of the gas will decrease. This is described by the First Law of Thermodynamics: ΔU = Q - W, where ΔU is the change in internal energy, Q is the heat added to the system, and W is the work done by the system. Since Q = 0 for an adiabatic process, ΔU = -W. This means that the internal energy of the gas decreases, which corresponds to a decrease in temperature, so choice E is false. The pressure of the gas will also decrease during an adiabatic expansion, so choice A is false.

During a Slow Adiabatic Expansion of a Gas