For B.Sc., Part I, II & III classes of all Indian Universities and also covering the UGC Curriculum including Solved Long type Answer type, Short Answer Type and Numerical Problems. • Collision frequency, mean free path, viscosity of a gases, various of a gas and barometric formula has been added. Structural differences between solids, liquids and gases, various intermolecular forces in liquids, hydrogen bonding and Piosellue's equation have been discussed in the chapter on liquid state. • Powder method and Laue's method for the determination of crystal structure have been added to chapter on solid state. Various kinds of heats of reaction, Hess' law of constant heat summation and bond energy have been discussed