# Matter: Specific Latent Heat

# Matter: Specific Latent Heat

## Understanding Specific Latent Heat

- The
**specific latent heat**of a substance refers to the amount of energy needed to change the phase (state) of 1 kg of the substance without changing its temperature. - Energy changes during phase transitions are due to changes in the
**potential energy**of the particles, not their kinetic energy.

## Specific Latent Heat and Changes of State

- There are two types of specific latent heat:
**latent heat of fusion**and**latent heat of vaporisation**. **Latent heat of fusion**is the energy required to change a substance from a solid to a liquid (melting) or vice versa (freezing) without a change in temperature.**Latent heat of vaporisation**is the energy needed to change a substance from a liquid to a gas (evaporating, boiling) or vice versa (condensing) without change in temperature.

## Calculating Specific Latent Heat

- The formula used to calculate energy, mass, specific latent heat is
**E = m * L**, where:- E = Energy transferred (Joules, J)
- m = Mass of the substance (Kilograms, kg)
- L = Specific latent heat (Joules per kilogram, J/kg)

- This formula can be rearranged to find any one of the values if the other two are known.

## Specific Latent Heat and Energy Conservation

- During phase transitions, the
**conservation of energy**principle still applies. As such, any energy that is absorbed or released due to a change of phase is balanced by a corresponding decrease or increase in the internal energy of the substance. - The energy supplied is not increasing the thermal (kinetic) energy of the particles but is being used to overcome intermolecular forces, hence the temperature does not change.