Kinetic Theory Of Gases: Assumptions

Gases are made up of molecules. What are molecules? Molecules are tiny independent unit which behaves the same as the sample, i.e. they have the same chemical properties as of the sample. The kinetic theory of gases has developed a model which explains the behavior of molecules, which should further explain the behavior of an ideal gas. Do you know what an ideal gas is?
We have learned that the pressure (P), volume (V), and temperature (T) of gases at low temperature follow the equation:

\(PV\) = \(nRT\)


n = number of moles in the gas
R = gas constant having value \(8.314 JK^{-1}mol^{-1}\)

Now, any gas which follows this equation is called ideal gas. Hence the equation is known as the ideal gas equation. But there are certain assumptions that we consider for describing ideal gas behavior.

kinetic Theory

Assumptions of Kinetic Theory of Gases

  • All gases are made up of molecules which are constantly and persistently moving in random directions.
  • The separation between the molecules is much greater than the size of molecules.
  • When a gas sample is kept in a container, the molecules of the sample do not exert any force on the walls of the container during the collision.
  • The time interval of collision between two molecules, and between a molecule and the wall is considered to be very small.
  • All the collisions between molecules and even between molecules and wall are considered to be elastic.
  • All the molecules in a certain gas sample obey Newton’s laws of motion.
  • If a gas sample is left for a sufficient time, it eventually comes to a steady state. The density of molecules and the distribution of molecules are independent of position, distance and time.

There is a lot more to be learned about kinetic theory of gases. Explore more on physics formulas and physics calculators at BYJU’S

Practise This Question

In the kinetic theory of gases, we try to relate macroscopic properties of a gas, like pressure, volume and temperature to its microscopic properties (properties of each atom or molecule) like particle speeds, momenta, kinetic energies, etc. Which of the following is/are incorrect assumption(s) for building the theory?