What happens to the density of a substance when it is heated and expands (Density of materials)

The correct answer is Density decreases.

Practical lens: Link apparatus, readings, and uncertainty to the exact measurement named in the objective. This question asks: What happens to the density of a substance when it is heated and expands (Density of materials). The correct response is Density decreases, because density links mass and volume, so the answer must preserve which quantity is being calculated. In Density of materials, the marking point should connect directly to describe how to determine the volume of a regular solid using length measurements. 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 Changes of state and the particle model, 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 74 is distinct because it uses this exact question context and the practical lens rather than a generic particle-model sentence.