Describe how the particle arrangement differs between solids, liquids, and gases.

In solids, particles are closely packed in a fixed arrangement and vibrate in place. In liquids, particles are still close but can move past each other, allowing them to flow. In gases, particles are far apart and move freely, resulting in no fixed shape.

Boundary lens: Keep this separate from nearby specification points that use similar words but test a different idea. This question asks: Describe how the particle arrangement differs between solids, liquids, and gases. The correct response is In solids, particles are closely packed in a fixed arrangement and vibrate in place. In liquids, particles are still close but can move past each other, allowing them to flow. In gases, particles are far apart and move freely, resulting in no fixed shape., 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 130 is distinct because it uses this exact question context and the boundary lens rather than a generic particle-model sentence.