Specific Latent Heat

The specific latent heat of a substance, is the amount of energy per kilogram required to change the state of said substance.

• The latent heat of fusion is the energy required for the state change: solid -> liquid (melting).

• The latent heat of vaporisation is the energy required for the state change: liquid -> gas (evaporation).

Equation

This equation will be on the Physics equation sheet!

$$E = mL$$

Where:

• $E$ is the energy for a state change, in Joules (J)
• $m$ is the mass, in kilograms (kg)
• $L$ is the specific latent heat, in Joules per kilogram (J/kg)

Example

For example, lets say I had 2.4kg of ice, and I wanted to melt it to liquid water. The latent heat of fusion for water is $33400 J/kg$, I want to know how much energy that will require.

$$\begin{align} E & = m * L \\ & = 2.4 * 33400 \\ & = 80160J \\ & = 80.16kJ \end{align}$$

Therefor I would need to use $80.16 kJ$ of energy to make the ice melt.

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