Which theory posits that particles are in constant motion, varying in speed depending on their state?

The kinetic theory is a fundamental concept in understanding the behavior of matter. It posits that all matter is composed of particles, which are in constant motion. This motion varies based on the state of the matter—solids, liquids, or gases—affecting the speed and arrangement of the particles. In solids, the particles vibrate in fixed positions, while in liquids, they move more freely, and in gases, they move rapidly and are more dispersed. This theory helps explain various physical properties, such as temperature, pressure, and volume in relation to particle movement.

This understanding of particle motion is essential for explaining phenomena such as temperature changes, phase transitions, and pressure changes, which can be observed in everyday life and are key to many scientific concepts in both chemistry and physics.