What is sublimation?

The correct answer is The process of a solid turning directly into a gas.

Cause lens: Name the cause, then state the effect on particles, pressure, density, or energy. This question asks: What is sublimation. The correct response is The process of a solid turning directly into a gas, 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 160 is distinct because it uses this exact question context and the cause lens rather than a generic particle-model sentence.