a substance's physical properties are highly dependent upon the attractive and repulsive forces of its molecules.
A substance having strong inter molecular force of attraction will be solid, have high strength, fixed shape and volume. High melting point.
A substance having moderate intermolcualr force of attractions will be liquid, will be able to flow, have no fixed shape but have fixed volume.
A substance having weak intermolecular forces of attractions will be gas, will be able to flow, no fixed shape and no fixed volume.
Also the properties like viscosity, surface tension , vapour pressure, boiling point, melting point all the properties depends upon the intermoleuclar force of attractions.
