What are the postulates of the kinetic theory of gases?

Postulates of the kinetic theory of gases: 

Following are the 13 postulates of kinetic theory of gases.

  1. Gas contains small individual particles called the molecules. They follow Newton’s laws of motion.
  2. The properties of the molecules of a gas are same, but different for different gases.
  3. The volume of a molecule is negligible when comparing with the distance between two molecules.
  4. The volume of all the molecules of a gas is too much small when comparing with the container of that gas.
  5. The molecules are perfectly hard elastic spheres.
  6. There is no attractive or repulsive force between the molecules. Hence, the energy of gas is kinetic energy.
  7. The molecules move always. There velocities vary within zero to infinity.
  8. Pressure forms in gas when the molecules strike with the walls of the gas container.
  9. The velocity of the molecules increases with temperature.
  10. The molecules move with same velocity through straight paths in the mean time of two strikes. The distance between any two consecutive strikes is called free path and the average distance is called the mean free path. If the pressure is high then the mean free path is less and if the pressure is low then the mean free path is more.
  11. The time of impact is negligible when comparing with the time taken to traverse the free path. The strikes of the molecules are instantaneous.
  12. The molecules can move in the whole volume of the container.
  13. The molecular density of an ideal gas is always constant.


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