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There are three common characteristics in the four processes of change of phase:
a) A substance undergoes a change of phase at a particular temperature.
b) Heat energy is transferred during change of phase.
c) During change of phase the temperature remains even though there is transfer of heat.
The heat absorbed or the heat released at constant temperature during a change of phase is known
as latent heat. The transfer of heat does not cause a change in the kinetic energy of the molecules.
Latent Heat of Fusion, Lf (melting/freezing)
During melting, the heat absorbed is used to break up the bonds between the particles. The
particles are freed from their fixed positions and are able to vibrate and move among each other as
particles of a liquid. The heat absorbed by melting solid is known as the latent heat of fusion. For a
liquid to solidify at its freezing point, latent heat of fusion has to be removed from it.
Figure 1.9
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