Properties of gases like liquefaction, expansibility, compressibility, diffusion or effusion, low densities etc. have been experimentally observed in gases. And various gas laws such as Charles law, Boyle’s law, etc. can also be experimentally studied. To explain these laws and properties of gases theoretically, various theoretical models of gas were made from time to time. The first model was given by Bernoulli in 1738 and later it was modified by various scientists according to their studies. The final model was given by Clausius in 1857 and was named as ‘Kinetic- molecular theory of gases’.
The main assumption or of postulates kinetic theory of gases is given as follows:
- A gas consists of a large number of small particles called molecules. Size and mass of all the molecules of a particular gas are identical but they vary from gas to gas.
- Distance between two consecutive molecules of a gas is very large.
- Force of attraction or repulsion acting between the molecules of a gas is negligible because of the large distance between the molecules.
- The molecules of gas have high kinetic energy due to which molecules moves continuously in different directions with different velocities. Thus they collide with each other and with the walls of the container.
- Pressure applied on the walls of the container is due to the collision of gas molecules with the container.
- The molecules of gases are supposed to be perfectly elastic.
- The molecules of gas moves with different velocities so they have different kinetic energies. The average kinetic energy of gas molecules depends on the temperature of gas.
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