What is the main reason gas particles exert pressure on the walls of a container?

Gas particles exert pressure on the walls of a container primarily due to their collisions with those walls. When gas particles move around in a container, they are in constant motion, and as they collide with the walls, they apply a force on the surface of the container. The cumulative effect of countless particles colliding with the walls results in the overall pressure that the gas exerts.

This concept is rooted in the kinetic theory of gases, which states that gas particles are in perpetual motion and that their kinetic energy contributes to the pressure. The more frequent and forceful the collisions with the walls, the higher the pressure will be in the container.

In contrast, while temperature can influence the speed of these particles (as higher temperatures increase kinetic energy and can lead to more collisions), it is not the direct reason for pressure. Gravity does play a role in the context of how gases behave in larger scales, such as in atmospheric pressure, but it is not the reason gas exerts pressure on walls at a molecular level. Similarly, external forces can affect the gas, but they do not directly account for the pressure exerted by the gas particles themselves.