As a liquid is heated, its vapor pressure increases until the vapor pressure
equals the pressure of the gas above it.
Bubbles of vaporized liquid (i.e., gas) form within the bulk liquid and
then rise to the surface where they burst and release the gas. (At
the boiling temperature the vapor inside a bubble has enough pressure to
keep the bubble from collapsing.)
In order to form vapor, the molecules of the liquid must overcome the forces
of attraction between them.
The temperature of a boiling liquid remains constant, even when more heat
is add.
