Physics – 2.2.3 Melting, boiling and evaporation | e-Consult

When heat is added to a substance, the potential energy of the molecules increases. This increased potential energy is converted into kinetic energy, causing the molecules to move faster. Temperature is a measure of the average kinetic energy of the molecules in a substance. Therefore, as the molecules gain kinetic energy, the temperature of the substance increases.

As the temperature of water increases from 0°C to 100°C, the water molecules gain kinetic energy and move faster. At 0°C, the molecules have relatively low kinetic energy and are held together by strong hydrogen bonds. As the temperature rises, the molecules vibrate more vigorously and eventually overcome the attractive forces of the hydrogen bonds, transitioning into the liquid phase. At 100°C, the molecules have enough kinetic energy to overcome the intermolecular forces and escape into the gaseous phase, resulting in boiling.