Describe how gas particles behave when the volume of the gas is increased at constant temperature.

Gas particles will continue to move in random motion, but with an increase in volume, they will collide with the walls of the container less frequently. The average distance between collisions increases, which corresponds to a decrease in pressure.

Boundary lens: Keep this separate from nearby specification points that use similar words but test a different idea. This question asks: Describe how gas particles behave when the volume of the gas is increased at constant temperature. The correct response is Gas particles will continue to move in random motion, but with an increase in volume, they will collide with the walls of the container less frequently. The average distance between collisions increases, which corresponds 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 526 is distinct because it uses this exact question context and the boundary lens rather than a generic particle-model sentence.