Explain why there is no rise in temperature of a substance when it undergoes a change of state although it is still being heated.

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Solution

Once the change in state of a substance starts (solid to liquid or liquid to gas), the temperature of the substance does not change. Actually, the heat energy now supplied does not increase the kinetic energy of the constituting particles but is used to change the state of the substance. It is absorbed either as latent heat of fusion or as latent heat of vaporization.
Example: Latent heat of vaporization is a physical property of a substance. It is defined as the heat required to change one mole of liquid at its boiling point under standard atmospheric pressure. It is expressed as kg/mol or kJ/kg.

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