heat is the energy given off or absorbed during a change of
phase. Whenever a substance changes form a gas to a liquid
or from a liguid to a solid this latent heat is given off.
Whenever a substance changes from a solid to a liquid or from
a liquid to a gas this latent heat is absorbed from the surroundings.
While a substance is changing phase, no temperature change
takes place. So as heat energy is added to or removed from
a substance, this heat energy is going either to sensible
heat (temperature change) or to latent heat (phase change),
but not both at once.
body uses latent heat during the summer as it sweats. As the
persperation evaporates, the vapor absorbs this latent heat
of vaporization from your body, cooling it.
heat of steam (water in the gaseous phase) is very high. This
makes steam an ideal subsatnce to transfer large amounts of
energy, both the latent heat as a gas, and as sensible heat
due to its high temperature.