In the previous sessions, we have discussed the basics of gas. In this section, we are going to discuss real and ideal gases.
Gases are categorised into,
  • Real gases and
  • Ideal gases
Real Gases:
Suppose the molecules or atoms of a gas interact with each other with a particular amount of intermolecular or inter-atomic force of attraction. In that case, the gases are said to be real gases.
A real gas behaves like an ideal gas at a very high temperature or low pressure because there is no interatomic or intermolecular force of attraction between molecules or atoms in this condition.
Any gas that exists is a real gas - oxygen, hydrogen, carbon dioxide, helium, carbon monoxide, etc.
Ideal Gases:
If the atoms or molecules of a gas do not interact or collide, then the gas is called an ideal gas or a perfect gas.
Practically, no gas is ideal. The molecules of any gas will have a particular amount of interaction among them. But, these interactions are minimal when the gases are at low pressure or high temperature. Because of this minimal interactions, the interatomic or intermolecular forces of attraction are lesser in an ideal gas.
Hence, a real gas at low pressure or high temperature can be termed as a perfect gas.
Examples of ideal gases are oxygen, nitrogen, carbon dioxide and other gases in Earth's atmosphere.
Ideal gases obey Boyle’s law, Charles’s law and Avogadro’s law. All these laws state the relationship between various properties of a gas such as pressure (P), volume (V), temperature (T) and the number of atoms (n).
In a given state of the gas, all these parameters will have a definite set of values. When there is a change in the gas state, any one or more of these parameters change its value.