Question

A gas exerts pressure on the walls of the containers

Answer 1

As we know that particles of matter are continously moving. While moving in air, the particles of gas collide with each other and also with the walls of container.

Answer 2

The molecules in a gas have large kinetic energy. Due to this, they strike the walls of the container with certain force and exert presure on them. The force per unit area is responsible for the pressure of the gas.