VAPOR PRESSURE
(also called SATURATION VAPOR PRESSURE)
The process of
evaporation in a closed container will proceed until there are as many molecules
returning to the liquid as there are escaping (equilibrium). At this point
the vapor is said to be saturated, and the pressure exerted by the vapor
(usually expressed in mmHg) is called the saturated vapor pressure.
Since the
molecules move faster (more kinetic energy) at higher temperature, more
molecules can escape the surface and the saturated vapor pressure is
correspondingly higher. i.e. higher the temperature, higher is the saturated
vapor pressure.
The temperature
at which the vapor pressure is equal to the atmospheric pressure is called the
boiling point.