Latent Heat

The total Thermal Energy absorbed or released when a substance changes state (measured in $J$)

Latent heat of fusion

The amount of Thermal Energy required to change a solid into a liquid or liquid into a solid $Q=m{L}_f$ $L_f$ is the specific latent heat of fusion (J/kg)

Latent heat of vaporization

The amount of Thermal Energy required to change a liquid into a gas or a gas into a liquid $Q=m{L}_v$ $L_v$ is the specific latent heat of vaporization (J/kg)

Important note

If a substance is warming up or cooling down but not changing state, use $Q=mc\Delta T$

Examples