- A gas is composed of a large number of molecules that are in constant, random motion due to which they collide with each other and with the walls of the container that the gas is present.
- As the gas molecules collide with the walls, they exert a force perpendicular to the walls. The sum of all such forces divided by the surface area of the container walls is called the Gas Pressure.
- The gas pressure is a measure of the average linear momentum of the gas molecules.
- The SI unit of gas pressure is pascal (Pa).
Hence, the gas pressure of a gas is the sum of the forces exerted on the walls of its container by the gas molecules divided by the total surface area of the container walls.