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# Specific latent heat

The specific latent heat ($\ell$) of a substance is the thermal energy absorbed or released when $1 \text{ kg}$ of a substance changes state at constant temperature.

The specific latent heat is given by:$$\Torange{\text{specific latent heat}}=\frac{\Tred{\text{thermal energy}}}{\Tblue{\text{mass}}} = \frac{\Tred{Q}}{\Tblue{m}}$$

The SI unit of specific latent heat is joules per kilogram ($\text{J} / \text{kg}$).

$\Tblue{0.2 \text{kg}}$ of ice absorbs $\Tred{60\,000 \text{J}}$ as it melts into water.

The specific latent heat is $\dfrac{\Tred{60\,000 \text{J}}}{\Tblue{0.2 \text{ kg}}} = \Torange{300\, 000} \text{ J}/\text{kg}.$

Latent heat is absorbed by ice when it melts into water