According to the kinetic molecular theory, what happens to gas molecules when their kinetic energy decreases?

• A. The molecules move more slowly and the temperature of the gas decreases.
• B. The volume of the gas increases at constant pressure.
• C. The molecules collide more frequently with the container walls.
• D. The molecules move faster and the temperature of the gas increases.

Answer: (A)

Verified step by step guidance

1. Recall that according to the kinetic molecular theory, the temperature of a gas is directly proportional to the average kinetic energy of its molecules. This means that if the kinetic energy decreases, the temperature also decreases.
2. Understand that kinetic energy of gas molecules is related to their speed. A decrease in kinetic energy means the molecules move more slowly.
3. Recognize that when molecules move more slowly, they collide less frequently and with less force against the container walls, so the pressure or volume behavior depends on the conditions but is not directly increased by decreased kinetic energy.
4. Note that volume changes depend on whether pressure or temperature is held constant, but a decrease in kinetic energy alone does not cause volume to increase at constant pressure without additional context.
5. Conclude that the correct interpretation is that when kinetic energy decreases, gas molecules move more slowly and the temperature of the gas decreases.