We have already learnt that intermolecular forces tend to keep the molecules together but thermal energy of the molecules tends to keep them apart.
Three states of matter are the result of balance between intermolecular forces and the thermal energy of the molecules.
When molecular interactions are very weak, molecules do not cling together to make liquid or solid unless thermal energy is reduced by lowering the temperature.
Gases do not liquify on compression only, although molecules come very close to each other and intermolecular forces operate to the maximum.
However, when thermal energy of molecules is reduced by lowering the temperature; the gases can be very easily liquified. Predominance of thermal energy and the molecular interaction energy of a substance in three states is depicted as follows:
We have already learnt the cause for the existence of the three states of matter. Now we will learn more about gaseous and liquid states and the laws which govern the behaviour of matter in these states.