Describe the particle arrangement and movement in a solid compared to a gas.

In a solid, particles are closely packed in a fixed arrangement and vibrate in place, maintaining a definite shape and volume. In contrast, gas particles are far apart, move freely and rapidly, and do not have a fixed shape or volume.

Unit lens: Check the units before giving the final statement so the physics quantity is not swapped. This question asks: Describe the particle arrangement and movement in a solid compared to a gas. The correct response is In a solid, particles are closely packed in a fixed arrangement and vibrate in place, maintaining a definite shape and volume. In contrast, gas particles are far apart, move freely and rapidly, and do not have a fixed shape or volume., because gas pressure comes from particle collisions with container walls. In Changes of state, the marking point should connect directly to explain sublimation as a change directly between solid and gas. 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 157 is distinct because it uses this exact question context and the unit lens rather than a generic particle-model sentence.