What happens to the density of a substance if its mass increases while its volume remains constant (Density of materials)

The correct answer is Density increases.

Boundary lens: Keep this separate from nearby specification points that use similar words but test a different idea. This question asks: What happens to the density of a substance if its mass increases while its volume remains constant (Density of materials). The correct response is Density increases, 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 recall and apply the equation density = mass divided by volume. 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 10 is distinct because it uses this exact question context and the boundary lens rather than a generic particle-model sentence.