This elegant book provides a student-friendly introduction to the subject of physical chemistry. It is concise and more compact than standard textbooks on the subject and it emphasises the two important concepts underpinning physical chemistry: quantum mechanics and the second law of thermodynamics. The principles are challenging to students because they both focus on uncertainty and probability. The book explains these fundamental concepts clearly and shows how they offer the key to understanding the wide range of chemical phenomena including atomic and molecular spectra, the structure and properties of solids, liquids and gases, chemical equilibrium, and the rates of chemical reactions.