Temperature & Heat: Latent Heat

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Latent Heat

The latent heat of a body is the amount of heat required to change its state without a change in temperature

As it is a form of heat energy, it is a scalar quantity and measured in Joules

Specific Latent Heat

The amount of heat required to change the state of 1 kg of a substance without a change in temperature

Scalar quantity

Unit = Joule per kilogram

Here is a graph illustrating latent heat

Fusion is a change of state from solid to liquid

Vaporisation is a change of state from liquid to gas

Q = ml

Q = energy (supplied or withdrawn)

m = mass of body

l = specific latent heat

Specific Latent Heat of Fusion

Amount of heat required to change 1 kg of a substance from a solid to a liquid without a change in temperature

3.3 x 10⁵ J/ kg

Specific Latent Heat of Vaporisation

Amount of heat required to change 1 kg of a substance from a liquid to a gas without a change in temperature

2.3. x 10⁶ J/ kg

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