The book is divided into 12 chapters, out of which first five chapters are related to kinetic theory and rest seven are related to thermodynamics and statistical physics. First and second chapters are related to ideal and real gases covering the laws of gases, deviation of real gas from ideal behaviour, J-T effect, Barometric equations. Chapter three provide the methods of liquefaction of gases and chapter four showing the transport phenomena in gases. Chapter five showing the Maxwellian distribution law for velocities and speeds in gases. Chapter six giving different laws used in thermodynamics, different types of system, practical and ideal heat engines, chapter eight and nine are concerned with statistical basis of thermodynamics and the phase space representation, covering an ideal of ensembles, division of phase space into cells, and Boltzmaan-entropy relations. Chapter ten is black body radiation, and eleven and twelve giving a bridge of statistical physics with thermodynamics and transition of classical statistics to quantum statistics.