Describe the arrangement and movement of particles in a solid.

In a solid, particles are closely packed together in a fixed arrangement. They vibrate in place but do not move freely, which gives solids a definite shape and volume.

Comparison lens: State both sides of the comparison so the contrast is explicit rather than implied. This question asks: Describe the arrangement and movement of particles in a solid. The correct response is In a solid, particles are closely packed together in a fixed arrangement. They vibrate in place but do not move freely, which gives solids a definite shape and volume., because gas pressure comes from particle collisions with container walls. In Changes of state, the marking point should connect directly to describe solids, liquids and gases in terms of particle arrangement and movement. 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 113 is distinct because it uses this exact question context and the comparison lens rather than a generic particle-model sentence.