Second law of thermodynamics: Direction of natural processes, Microscopic and macroscopic systems, Statistical weight of a macrostate, Equilibrium of isolated system (microcanonical Ensemble) and system in a Heat Bath (canonical Ensemble), Second law for infinitesimal changes, Clausius inequality. Perfect classical gas: Partition function;,Equation of state, Specific heat capacities, Entropy. Perfect quantum gas: Quantum Statistics, Partition function and its classical limit, Free electron model of metals, Fermi-Dirac distribution, Bose-Einstein distribution, Black-body radiation. Open systems: Grand Canonical Ensemble, Grand partition function, Partition function of a classical and quantum gas, Fluctuations.