Using the particle model, explain why gases are less dense than solids or liquids.

Gases are less dense than solids or liquids because the particles in gases are much further apart compared to those in solids and liquids. In solids, particles are closely packed in a fixed arrangement, while in liquids, they are still close but can move past each other. In gases, the particles have more energy and move freely, resulting in a larger volume and lower density.

Application lens: Apply the rule to the specific sample or situation instead of reciting a broad fact. This question asks: Using the particle model, explain why gases are less dense than solids or liquids. The correct response is Gases are less dense than solids or liquids because the particles in gases are much further apart compared to those in solids and liquids. In solids, particles are closely packed in a fixed arrangement, while in liquids, they are still close but can move past each other. In gases, the particles have more energy and move freely, resulting in a larger volume and lower density., because gas pressure comes from particle collisions with container walls. In Changes of state, the marking point should connect directly to use the particle model to explain why gases are less dense than solids or liquids. 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 199 is distinct because it uses this exact question context and the application lens rather than a generic particle-model sentence.