After the introduction in this chapter first we learn about intermolecular forces( dispersion or London forces, dipole-dipole forces, dipole-induced dipole forces). Then we learn about thermal energy then about the difference between intermolecular forces and thermal interactions. Then we discuss about Gaseous state then about the gas laws :- Boyle’s Law, Charles’ Law, Gay Lussac’s law, Avogadro Law; then about Ideal Gas Equation. Then we know about the Kinetic Molecular Theory Of Gases, behaviour of real gases and its deviation from ideal gas behaviour. Then we discuss liquification of gases and finally we discuss about liquid state, vapour pressure, surface tension and viscosity.