Latent Heat Calculator

Latent heat is the hidden energy of a change of state, the energy a substance soaks up to melt or boil, or gives back when it freezes or condenses, all without its temperature changing at all, and this calculator works out how much that takes using the simple relationship Q equals mass times specific latent heat. Choose a common substance and change of state from the list to load a typical latent heat value, or type your own, enter the mass, and it returns the energy required in joules and kilojoules, updating as you type. The idea behind it is one of the more surprising in physics. When you heat ice at zero degrees, the temperature stubbornly stays at zero until every last bit has melted; all the energy you pour in goes not into making molecules move faster, but into breaking the bonds that hold them in a solid. Only once the change of state is complete does the temperature start to rise again. The same happens, on a much larger scale, when water boils, which is why steam carries so much energy and why sweating cools you so effectively. The specific latent heat is the energy needed per kilogram for a particular substance and change, and it differs between melting, called fusion, and boiling, called vaporisation, with vaporisation usually demanding far more. That makes this tool genuinely useful for physics students learning about heat and changes of state and checking homework, and for practical estimates in cooking, refrigeration, heating and engineering, wherever something is melted, frozen, boiled or condensed. Using kilograms and joules per kilogram gives the energy in joules. The formula and a worked example are explained clearly below.

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