Essentials of Thermodynamics offers a fresh perspective on classical thermodynamics and its explanation of natural phenomena. It combines fundamental principles with applications to offer an integrated resource for students, teachers and experts alike. The essence of classic texts has been distilled to give a balanced and in-depth treatment, including a detailed history of ideas which explains how thermodynamics evolved without knowledge of the underlying atomic structure of matter. The principles are illustrated by a vast range of applications, such as osmotic pressure, how solids melt and liquids boil, the incredible race to reach absolute zero, and the modern theme of the renormalization group. Topics are handled using a variety of techniques, which helps readers see how concepts such as entropy and free energy can be applied to many situations, and in diverse ways. The book has a large number of solved examples and problems in each chapter, as well as a carefully selected guide to further reading. The treatment of traditional topics like the three laws of thermodynamics, Carnot cycles, Clapeyron equation, phase equilibria, and dilute solutions is considerably more detailed than usual. For example, the chapter on Carnot cycles discusses exotic cases like the photon cycle along with more practical ones like the Otto, Diesel and Rankine cycles. There is a chapter on critical phenomena that is modern and yet highly pedagogical and contains a first principles calculation of the critical exponents of Van der Waals systems. Topics like entropy constants, surface thermodynamics, and superconducting phase transitions are explained in depth while maintaining accessibility for different readers.