When a solid changes the phase gets into a liquid it does so by “eating up” heat. Also, when a liquid changes its phase and gets into a solid, it does so by “vomiting” heat. this eaten/vomited heat is called the latent heat. When a solid melts you call that the latent heat of melting and when a liquid solidifies then you call that the latent heat of fusion.
Interesting things happen when a material solidifies or when it gets molten. Because we know that energy is never lost, it only gets transformed aka conservation of energy, we now know how to obtain materials that can help us thermally insulate our homes.
Two quick things to remember:
– liquid => solid + heat – when a liquid becomes solid it releases heat into the medium
– solid + heat => liquid – when you add heat to a solid, then it becomes a liquid
Take parafin wax for example: if you have a black roof made of asphalt, then ti will get pretty hot. Inserting this wax into the cellulose insulation you will see that during the day the wax absorbs heat and becomes a liquid, but during the night it releases that heat and becomes solid.
Ain’t that nice? Science being practical all the way 😀