Heat required to vaporize one mole of a substance at its Temperature at which the vapor pressure of a liquid is equal to the ambient pressure - thus, the boiling point depends on pressure. A liquid may change to a gas at temperatures below the boiling point by evaporation. However, evaporation is a surface phenomenon where only molecules located near the Click on Term to Read More under standard pressure (101,325 Pa). The Equivalent to heat of vaporization, and latent heat of a substance. It is the amount of heat that must be removed from one gram of a vapor at its condensation point to condense the vapor with no change in temperature. Click on Term to Read More is expressed in kJ/mol.