What is the primary reason for the change of state from liquid to gas during boiling (Changes of state)

The correct answer is Particles gain enough energy to separate throughout the liquid..

Definition lens: Give the precise definition, then add a context sentence that shows how it is used. This question asks: What is the primary reason for the change of state from liquid to gas during boiling (Changes of state). The correct response is Particles gain enough energy to separate throughout the liquid., because changes of state are explained by particle energy and arrangement. In Changes of state, the marking point should connect directly to explain melting using increased 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 126 is distinct because it uses this exact question context and the definition lens rather than a generic particle-model sentence.