Kinetic theory of gases

Discovered by Daniel Bernoulli

Kinetic theory of gases:-

The kinetic theory of gases describes a gas as a large number of submicroscopic particles (atoms or molecules), all of which are in constant, rapid, random motion. The randomness arises from the particles' many collisions with each other and with the walls of the container.


Kinetic theory of gases explains the macroscopic properties of gases, such as pressure, temperature, viscosity, thermal conductivity, and volume, by considering their molecular composition and motion. The theory posits that gas pressure results from particles' collisions with the walls of a container at different velocities.


The kinetic molecular theory defines temperature in its own way, in contrast with the thermodynamic definition.[1]


Under an optical microscope, the molecules making up a liquid are too small to be visible. However, the jittery motion of pollen grains or dust particles in a liquid is visible. Known as Brownian motion, the motion of the pollen or dust results from their collisions with the liquid's molecules.


  1. The gas consists of very small particles known as molecules.

  2. These particles have the same mass.

  3. The number of molecules is so large that statistical treatment can be applied.

  4. The rapidly moving particles constantly collide among themselves and with the walls of the container. All these collisions are perfectly elastic.

  5. Except during collisions, the interactions among molecules are negligible.

  6. The average kinetic energy of the gas particles depends only on the absolute temperature of the system. 

  7. The elapsed time of a collision between a molecule and the container's wall is negligible when compared to the time between successive collisions.

  8. There is a negligible gravitational force on molecules.