Why is energy required for the boiling process?

1 Answer

Boiling water is an endothermic process, which supplies heat to the water molecules, increasing their potential energy. The applied heat causes the water molecules to move further away from each other without causing any increase in overall temperature.

More specifically, the applied heat goes into breaking the intermolecular bonds between the water molecules, speading the molecules further and further apart. When all the intermolecular bonds are broken, the water turns completely to steam (water vapor).

This sort of physical process is called a phase change. Once the intermolecular bonds are broken, any extra heat increases the kinetic energy of the system and the molecules of the water vapor move faster as the temperature increases.

But heat is also required -- and generated -- by chemical processes. For chemical processes, the heat supplied, among other things, helps the reactants overcome activation energy, which is the energy needed to get a reaction started.