A fixed container containing an ideal gas is heated. The pressure of the gas increases because:

• A. the average kinetic energy of the gas molecules increases, causing more frequent and forceful collisions with the container walls
• B. the volume of the container expands as the temperature rises
• C. the number of gas molecules in the container increases
• D. the gas molecules lose energy and move more slowly

Answer: (A)

Verified step by step guidance

1. Understand the relationship between pressure, volume, temperature, and the behavior of gas molecules in a fixed container. Since the container is fixed, the volume does not change.
2. Recall that pressure in a gas arises from collisions of gas molecules with the container walls. The force and frequency of these collisions determine the pressure.
3. Recognize that heating the gas increases the temperature, which increases the average kinetic energy of the gas molecules. This means molecules move faster.
4. Faster-moving molecules collide more frequently and with greater force against the container walls, leading to an increase in pressure.
5. Conclude that the pressure increase is due to the increased average kinetic energy of the gas molecules, not changes in volume or number of molecules.