At room temperature the forces of attraction between the particles of solid substances are stronger than those which exist in the gaseous state.
- The forces of attraction between the particles of a gas are minimum, intermediate in case of a liquid and are maximum in a solid.
- Hence, in case of oxygen ‘forces of attraction’ are minimum since it is a gas.
- On increasing the temperature of solids, the kinetic energy of the particles increases.
- Due to the increase in kinetic energy, the particles start vibrating with greater speed.
- The energy supplied by heat overcomes the forces of attraction between the particles.
- The particles leave their fixed positions and start moving more freely.