Preliminary concepts, probability theory, introduction to central limit theorem, random walk problem, quasi-static process,thermal and mechanical interactions, laws of thermodynamics, thermodynamic potentials. Statistical description of a system of particles,microstates, concept of ensembles, basic postulates, phase space, Liouville's theorem, microcanonical, canonical and grand canonical ensembles. Partition functions. Chemical potential,free energy and connection with thermodynamic variables. Equivalence of ensembles. Ideal gas,Gibbs paradox, M-B gas velocity distribution. Equipartition theorem, Formulation of quantum statistics,density matrix, ensembles in quantum statistical mechanics. Identical particles, Maxwell-Boltzmann,Bose-Einstein and Fermi-Dirac statistics. Black body radiation,Stefan-Boltzmann law, Wien's displacement law, Einstein and Debye’s theories of specific heat of solids. Ideal Bose gas, Bose-Einstein condensation, Ideal Fermi gas.Ideal gases in the classical limit. Introduction to first and second order phase transitions.