The difference between ideal and real gas.

Researchers distinguish ideal and real gas models. What is their specificity?

What is an ideal gas?

In science, the interpretation of the concept of "ideal gas" is widespread, corresponding to a hypothetical substance (which does not exist in reality), the properties of which can be described by means of the Clapeyron - Mendeleev equation.

Under an ideal gas is understood a mathematical model of the corresponding substance, which is characterized by:

  • the possibility of neglecting the potential energy generated in the process of interaction of gas particles - in comparison with the level of kinetic the energies of these particles;
  • the extremely small total volume of the particles constituting the gas;
  • very small presence or absence of remote forces of attraction of particles or their repulsion;
  • very short time of interaction of particles with each other.

What is real gas?

Under a real gas, in turn, we mean a substance that cannot be described by the Clapeyron – Mendeleev equation. So, the molecules present in it interact with each other, form a certain volume.

It should be noted that in many cases the characteristics of the potential energy formed during the interaction of real gas molecules are significantly lower than the kinetic energy. As a result, the corresponding gases in their properties approach those that characterize an ideal gas. Significant differences between the substances under consideration begin to appear, as a rule, with an increase in pressure and a decrease in temperature.


The main difference between an ideal gas and a real one is that the model of the first substance practically does not take into account the volume of molecules, as well as the energy of their interaction. In real gas, the corresponding indicators are taken into account. At the same time, at low pressure and high temperature, the real gas is close to ideal in its properties.

Having determined what is the difference between ideal and real gas, let us fix the conclusions in the table.


Ideal gas Real gas
What do they have in common?
Under certain conditions, a real gas can be close in properties to ideal
difference between them?
The model for describing a substance does not take into account the volume of its molecules, as well as the energy of their interaction with each otherThe model for describing a substance takes into account the volume of its molecules and the strength their interactions