Latent heat is the energy absorbed or released in the form of heat by a substance when it changes its physical state (i.e., solid, liquid, or gas). The change associated with the solid-liquid transition is called the latent heat of fusion (melting), and the change associated with the liquid-gas transition is called the latent heat of evaporation (boiling). The International System of Units (SI) for latent heat is joules per kilogram or kilojoules per kilogram (kJ/kg). Because 1 cal/g (calorie per gram) = 4.185 kJ/kg, for pure water, the latent heat of melting of 65 cal/g = 272 kJ/kg and the latent heat of evaporation at 10 °C of 425 cal/g = 1.78 × 103 kJ/kg. It is important to note that the amount of ...