What occurs when gas particles collide with the walls of their container (Pressure in gases (physics only))

The correct answer is They exert a force on the walls.

Unit lens: Check the units before giving the final statement so the physics quantity is not swapped. This question asks: What occurs when gas particles collide with the walls of their container (Pressure in gases (physics only)). The correct response is They exert a force on the walls, 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) Apply MS 3b, MS 3c and MS 4a skills when calculating or interpreting pressure-volume relationships. 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 577 is distinct because it uses this exact question context and the unit lens rather than a generic particle-model sentence.