What happens to the pressure of a fixed mass of gas when its volume decreases at constant temperature (Pressure in gases (physics only))

The correct answer is The pressure increases.

Definition lens: Give the precise definition, then add a context sentence that shows how it is used. This question asks: What happens to the pressure of a fixed mass of gas when its volume decreases at constant temperature (Pressure in gases (physics only)). The correct response is The pressure increases, 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) Interpret pressure-volume data for a fixed mass of gas at constant temperature. 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 570 is distinct because it uses this exact question context and the definition lens rather than a generic particle-model sentence.