What occurs to the mass of a substance when it changes state?

The correct answer is Mass is conserved during changes of state.

Evidence lens: Use the data, graph feature, practical observation, or particle behaviour that proves the answer. This question asks: What occurs to the mass of a substance when it changes state. The correct response is Mass is conserved during changes of state, because changes of state are explained by particle energy and arrangement. In Changes of state, the marking point should connect directly to explain freezing using decreased particle energy and changed particle arrangement. 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 129 is distinct because it uses this exact question context and the evidence lens rather than a generic particle-model sentence.