Why do gases flow easily according to the particle model?

The correct answer is Particles are loosely packed and move freely in all directions..

Exam lens: Write the relationship, substitute values only when needed, and finish by interpreting the result. This question asks: Why do gases flow easily according to the particle model. The correct response is Particles are loosely packed and move freely in all directions., 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 solids have fixed shapes and liquids and gases flow. 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 191 is distinct because it uses this exact question context and the exam lens rather than a generic particle-model sentence.