At a given temperature, a substance in the liquid phase has the tendency to change into the gaseous phase without reaching its boiling point through the process called evaporation. Liquid molecules have intermolecular bonds. With sufficient heat energy, these bonds tend to dissociate, releasing the molecules into the gaseous phase. This process happens at the surface of the liquid. This is because the surface is in close contact with the atmosphere and heat energy can be easily absorbed. Evaporation happens below the boiling point of the liquid. Only the liquid molecules which are at the surface, absorb energy from the atmosphere to break their intermolecular bonds and go into the gaseous phase. Molecules at the bulk of the liquid only get evaporated when they reach the surface and get exposed to the atmosphere. The rate of evaporation is directly associated with the strength of intermolecular bonds between the liquid molecules. When the strength of intermolecular bonds is high, the liquid is less volatile. Liquids with weak intermolecular bonds are highly volatile. Water molecules are less volatile due to the strong hydrogen bonds between the molecules. Non-polar organic compounds do not have such strong intermolecular attractions. They have Van Der Waals bonds which are comparatively weak. Therefore, the liquid molecules can easily go into vapour phase. Most non-polar organic liquids are highly volatile.