How is the Hfusion used to calculate the energy needed to melt a mass of
solid?

Evaporation: this is when warmth from the sun causes water from oceans, lakes, streams, ice and soils to rise into the air and turn into water vapour (gas). water vapour droplets join together to make clouds! condensation: this is when water vapour in the air cools down and turns back into liquid water.

Because a model would make the investigation easier to understand