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Heat of Fusion-the amount of heat required to convert unit mass of a solid into the liquid without a change in temperature. (or released for freezing)

For water at its normal freezing point of 0 ºC, the specific heat of Fusion is 334 J g^-1. This means that to convert 1 g of ice at 0 ºC to 1 g of  water at 0 ºC, 334 J of heat must be absorbed by the water. Conversely, when 1 g of water at 0 ºC freezes to give 1 g of ice  at 0 ºC, 334 J of heat will be released to the surroundings.

Heat of Fusion of Water (H_f = 334 J /g)

q= m H_f

Note- The Heat of Fusion equation is used only at the melting/freezing transition, where the temperature remains the same only and that is why there is no temperature change (DT) in this formula. It stays at 0 Celsius for water.

Note #2-Energy is required to melt and released when it freezes

The diagram on the left shows the uptake of heat by 1 kg of water, as it passes from ice at -50 ºC to steam at temperatures above 100 ºC, affects the temperature of the sample. E: Steam absorbs heat and thus increases its temperature. D: Water boils and absorbs latent heat of vaporization. C: Rise in temperature as liquid water absorbs heat. B: Absorption of latent heat of fusion. A: Rise in temperature as ice absorbs heat. from-http://www.physchem.co.za/Heat/Latent.htm

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