Specific latent heat of fusion
Here is the formula:
Eh = m x l
Eh means energy, equals m for mass, times l.
l is the specific latent heat of fusion for that material.
So the formula tells us how much heat energy is needed to go into a material to change it from a solid to a melted liquid. If you apply heat to ice, it will melt. If you put a thermometer into the mixture you will see the temperature gradually rise, and then stop. The temperature remains the same for a while and then it rises again. The reason this happens is that a lot of energy is needed to break the bonds between the particles in the solid to change it to a liquid. When all the bonds are broken, the temperature rises again. The time when the temperature doesn't rise, even though more heat is going in, that's when the material melts.