Explain why increasing the volume of a gas at constant temperature decreases its pressure.

When the volume of a gas increases at constant temperature, the gas particles have more space to move. This results in fewer collisions between the gas particles and the walls of the container, leading to a decrease in pressure.

Unit lens: Check the units before giving the final statement so the physics quantity is not swapped. This question asks: Explain why increasing the volume of a gas at constant temperature decreases its pressure. The correct response is When the volume of a gas increases at constant temperature, the gas particles have more space to move. This results in fewer collisions between the gas particles and the walls of the container, leading to a decrease in pressure., because density links mass and volume, so the answer must preserve which quantity is being calculated. In Pressure in gases (physics only), the marking point should connect directly to (Physics only) Explain why increasing the volume of a gas at constant temperature decreases its pressure. If the question includes values, the working must keep the appropriate unit and operation; if it is an explanation, it must name the relevant particle behaviour or energy change. This item belongs to Particle model and pressure, so avoid answers that switch to a different quantity, confuse heat with temperature, or describe gas pressure without collisions when collisions are the reason. Checkpoint 529 is distinct because it uses this exact question context and the unit lens rather than a generic particle-model sentence.