energy
It is the latent heat of liquefaction.
endothermic
Heat of Fusion
Usually heat is needed. but this can happen through osmosis as well.
heat is a mesure of energy the more energy the hotter it is so depending on its melting point is how much energy/heat is needed
either potential or kinetic
The energy needed to change a substance from a liquid to a gas is called the enthalpy (or heat) of vaporization.
heat of vaporization
You can add heat and cause liquid to gasify. Or you can decrease the pressure in the system and cause liquid to gasify. Note that you may gasify liquid and leave suspended or dissolved solids behind. More heat or pressure may be required to convert these remnants to liquid and then gas.
liquid
Heat of fusion. (I have no idea what the "propane or water" part is supposed to mean.)
Thermal Energy