## Pressure

Pressure is the amount of force exerted per area.

As the temperature increases, pressure increases as the molecules strike the wall of the container more frequently and this gives a GREATER CHANGE IN MOMENTUM. As the change in momentum increases per second, the force exerted increases and therefore provides a greater pressure for a constant surface area.

**Measuring pressure **

1)**Mercury barometer **

The pressure at beneath a liquid surface (and therefore at the base of the mercury column) can be calculated with the following formula:

Pressure beneath liquid surface = ρgh

[ρ = density (kg/m^{3}), g = acceleration due to gravity (10 m/s^{2}), h = depth (m)]

2) **Manometer**

Pressure due to gas = atm + ρgh

[ρ = density (kg/m^{3}), g = acceleration due to gravity (10 m/s^{2}), h = depth (m)]

[atm = atmospheric pressure]