Explain how the particle model can be used to describe why gases are less dense than solids or liquids.

The particle model shows that gas particles are much further apart than those in solids or liquids, leading to lower density. In solids, particles are closely packed and vibrate in fixed positions, while in liquids, they are closer together but can move past each other. In gases, the large distances between particles result in lower mass per unit volume.

Graph lens: Read the trend, flat section, gradient, or axis labels before explaining the physical meaning. This question asks: Explain how the particle model can be used to describe why gases are less dense than solids or liquids. The correct response is The particle model shows that gas particles are much further apart than those in solids or liquids, leading to lower density. In solids, particles are closely packed and vibrate in fixed positions, while in liquids, they are closer together but can move past each other. In gases, the large distances between particles result in lower mass per unit volume., because the particle model explains the observable property using particles. In Changes of state, the marking point should connect directly to describe limitations of simple particle model diagrams for representing real particles, forces and motion. 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 207 is distinct because it uses this exact question context and the graph lens rather than a generic particle-model sentence.