Water

1
Air pressure
Water Vapor pressure
Pressure boiling point relationship
2
The Boiling Point of Water

• As energy is transferred from a heating
  device to the water, the kinetic energy of the
  water molecules increases and the molecules
  become more mobile. If the kinetic energy is
  large enough to break the intermolecular forces
  of attraction between water molecules in the
  liquid phase then the molecules can escape in the
  form of water vapor. This is indicated by
  bubbles forming near the bottom of the container
  of water, nearest to the heat source. These
  gaseous water molecules exert a force on the
  atmosphere, called the vapor pressure. The vapor
  pressure is opposed by another force, created by
  a column of air pushing down on the surface of
  the water. This pressure is the atmospheric
  pressure.

3

• The atmospheric pressure will
  initially squash the pressure of the water vapor
  causing the bubbles to burst, but as more energy
  is provided the pressure exerted by the bubbles
  will exceed the atmospheric pressure and the
  bubbles of water vapor will escape the surface of
  the liquid. A diagram of these forces is
  provided. Water begins to boil. The temperature
  at which water boils is related to the vapor
  pressure required for boiling, which is equal to
  the atmospheric pressure. The implication of
  this is that as the atmospheric pressure changes,
  the boiling point of water changes as well. When
  you go up a mountain, the air pressure is lower
  (the column of air pushing downward is less) and
  water boils at a lower temperature.

4
Air pressure
Water Vapor pressure
Pressure boiling point relationship
5
Air pressure
Water Vapor pressure
Pressure boiling point relationship
6
Air pressure
Water Vapor pressure
Pressure boiling point relationship