Random motion

A gas may look still, but its molecules are in constant random motion. They travel in different directions and continually collide with one another and with the walls of their container. Between collisions, a molecule moves through the space inside the container.

A gas can be modelled as a very large number of tiny particles with spaces between them. These particles are in constant random motion. They travel through the container in many different directions and repeatedly collide with one another and with its walls.