Vapor pressure is the pressure exerted by the vapor present above the liquid in equilibrium with the liquid at that temperature. It is a measure of the tendency of a material to change into the gaseous or vapor state, and it increases with temperature. The equilibrium vapor pressure is known to serve as an indicator of the evaporation rate of a liquid. The propensity of particles to escape from the liquid (or a solid) is known to be related to vapor pressure.
The vapor pressure of a liquid can be measured in various ways, and the simplest method is using a manometer in a closed container or flask. The most common unit for vapor pressure is the torr, and most materials have external vapor pressures. For example, water has a vapor pressure of approximately 20 torrs at room temperature (22 °C = 72 °F), and the vapor pressure increases with temperature.
In summary, vapor pressure is the pressure exerted by the vapor present above the liquid in equilibrium with the liquid at that temperature. It is a measure of the tendency of a material to change into the gaseous or vapor state, and it increases with temperature.
