A brief overview of the equilibrium statistical mechanics. Recap of the ideal gas law. Corrections to the ideal gas law. The van der Waals equation of state. Two phase coexistence. The Maxwell rule. The Flory-Huggins theory of polymer solutions. Phase transitions and phase diagrams. Metastable states. Application to chemical reactions. Chemical equilibrium in solutions. Derivation of the Dalton, Raoult, Henry and Van't-Hoff laws. Concepts of the non-equilibrium statistical mechanics. Kinetics of phase transitions.