What is the formula for calculating density?

The correct answer is Density = mass / volume.

Definition lens: Give the precise definition, then add a context sentence that shows how it is used. This question asks: What is the formula for calculating density. The correct response is Density = mass / volume, because the particle model explains the observable property using particles. In Density of materials, the marking point should connect directly to required practical activity 5: use appropriate apparatus to make and record measurements needed to determine densities of regular solid objects. 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 54 is distinct because it uses this exact question context and the definition lens rather than a generic particle-model sentence.