Kinetic Theory of Gases

The gas laws describe what gases do — how pressure, volume, and temperature are related. Kinetic theory explains why they behave this way, by modelling a gas as a collection of tiny particles (molecules) moving randomly and colliding with each other and the walls of their container.

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Assumptions of the Kinetic Theory Model

The kinetic theory of gases is built on a set of simplifying assumptions. These are crucial to understand and are frequently examined:

1. A gas contains a very large number of identical molecules. The sheer number (on the order of 10²³ or more) ensures that statistical averages are meaningful.

2. The molecules are in constant, random motion. They move in all directions with a range of speeds. There is no preferred direction of motion.

3. Collisions between molecules, and between molecules and the container walls, are perfectly elastic. This means kinetic energy is conserved in every collision. No energy is lost to deformation, heat, or sound.

4. The volume of the molecules themselves is negligible compared to the volume of the container. The molecules are treated as point particles — almost all the space in the container is empty.