What happens to a gas sample's average kinetic energy when heated at constant pressure?

When a gas sample is heated at constant pressure, its average kinetic energy increases. This is based on the kinetic molecular theory, which states that the temperature of a gas is directly proportional to the average kinetic energy of its molecules. When you heat the gas, the energy added to the system increases the speed of the gas molecules, which results in higher kinetic energy.

Since the heating occurs at constant pressure, the gas cannot maintain its original volume; instead, it must expand. According to Gay-Lussac’s Law, as the temperature of a gas increases at constant pressure, its volume also increases. Therefore, both the average kinetic energy and the volume increase as a result of heating the gas.

This understanding aligns perfectly with the correct choice, which states that the average kinetic energy increases and the volume of the gas increases.