What does kinetic molecular theory explain?

Kinetic molecular theory fundamentally describes the behavior of matter in terms of the motion of its particles. This theory posits that all matter is made up of tiny particles that are in constant motion. The state of matter—solid, liquid, or gas—depends largely on the arrangement and movement of these particles. In solids, particles are closely packed and vibrate in place, while in liquids, they are more loosely arranged, allowing for greater movement. In gases, the particles are far apart and move freely at high speeds.

The theory also explains how temperature affects these states, as increasing temperature generally leads to increased particle motion, which can cause a solid to melt into a liquid or a liquid to evaporate into a gas. Thus, the correct answer emphasizes that kinetic molecular theory encompasses the behavior of all states of matter, based on the movement of particles, making it a broad and comprehensive explanation rather than one confined to gases or other specific conditions.