Kinetic Molecular Theory Of Gases

Kinetic Molecular Theory of Gases

Kinetic Molecular Theory of Gases

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 postulates of Kinetic Molecular Theory Of Gases is given as follows:

  1. 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.
  2. The 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.
  1. The molecules of gas have high kinetic energy due to which molecules move continuously in different directions with different velocities. Thus they collide with each other and with the walls of the container.
  2. Pressure applied to the walls of the container is due to the collision of gas molecules with the container.
  3. The molecules of gases are supposed to be perfectly elastic.
  • The molecules of a gas move with different velocities so they have different kinetic energies. The average kinetic energy of gas molecules depends on the temperature of the gas.

This was just a brief layout of the kinetic theory of gases. To know more about this topic by working on solved questions and answers by visiting NCERT solutions for Kinetic theory of gases.


Practise This Question

Imagine a gravity free laboratory, in outer space, where you are asked to study the motions of a large number of marbles kept in a transparent cubical jar, as you give the jar quick, small jerks in random directions. You will observe, that after giving a sufficient number of jerks, the marbles start moving rather chaotically, i.e., each marble bounces off other marbles every now and then, and takes a random trajectory between two points due to these collisions. You seem to have given some kinetic energy to each marble, when the jar was being shaken. What happens when you release the jar suddenly, leaving it suspended in space? Assume all collisions between the marbles to be perfectly elastic.