Latent heat is the amount of energy required for the phase change of a substance without a change in its temperature, or the amount of energy absorbed or released during a phase change. The commonly encountered phases are solid, liquid and gas. The latent heat of vaporization is defined as the amount of heat required to change a substance from liquid phase to gas phase, without changing its temperature. For example, the latent heat of vaporization of water is 539 cal/g or 2256 KJ/kg. This means that when we heat the water and raise its temperature to its boiling point (100 degrees Celsius), it will still be water (liquid). We will need to supply 539 cal/g of additional heat to convert it to water vapor. During this change of phase, the temperature of water will stay constant.
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