Liquid to gas state conversion takes place by the absorption of heat energy and is called Vaporization. The temperature remains same during the phase change and hence, the entire energy absorbed is used to increase the volume of the liquid i.e. the spacing between the atoms (as gases have very low density and have large atom spacing).
Gas to liquid state conversion takes place by the releasing of heat energy and is called Condensation. The temperature remains same during the phase change and hence, the entire energy is released by decreasing the volume of the gas i.e. the spacing between the atoms (as liquids have higher density and have lesser atom spacing).
Energy will be released to change from liquid to solid (fusion), gas to liquid (condensation), or gas to solid. Latent heat of evaporation is the energy used to change liquid to vapor. IMPORTANT: The temperature does not change during this process, so heat added goes directly into changing the state of the substance
