The (latent) heat of vaporization is also another term for enthalpy for vaporization. This is the energy that is needed for a certain substance to change in phase while maintaining its temperature. In this case, the phase change is from liquid to gas. To solve this we just have to divide the amount of energy by the amount of the substance. The answer is 2.26 KJ/gram of water. This means it takes 2.26 KJ of energy to vaporize 1 gram of water.