The present book covers material in intermediate thermodynamics. It is aimed at those students who desire a deep fundamental understanding of the subject of thermodynamics. It is assumed that the student is familiar with differential equations and has completed a first course in thermodynamics. The material covered in the book is in four parts. In Part I, consisting of Lectures 1 and 2, we cover fundamental concepts of thermodynamics. These lectures provide a brief overview of the subject of thermodynamics, the generality, the applicability, how it's related to the composition of matter, and the laws of thermodynamics. Dimensions and units of various quantities, the definitions of a system, the boundary, the surroundings, constraints, and processes, as well as thermodynamic postulates which lead to the definition of entropy, the fundamental relation, and the energy minimum principle are also introduced in these lectures.Part II, consisting of Lectures 3 through 9, covers the theoretical basis of thermodynamics. Lecture 3 discusses the fundamental relation, the Euler equation, the equations of state, as well as the equilibrium state. Lecture 4 discusses the Gibbs-Duhem relation, molar coordinates, the ideal gas, generalized compressibility, and the virial equations of state. Lecture 5 provides an application of basic concepts to obtain the fundamental relation of the van der Waals fluid. Additional forms of the fundamental relation which are more useful in applications (the Helmholtz free energy, the enthalpy, and the Gibbs free energy), obtained via Legendre transformations, and a discussion on the chemical potential are given in Lectures 6 and 7. Lecture 8 discusses the number of properties necessary to fully describe a system, and the relationship between Maxwell relations and the restrictions on such properties. Lastly, Lecture 9 discusses the concept of thermodynamic stability and the Le Chatelier and Le Chatelier-Braun principles. Part III consists of Lectures 10 through 14 and deals with phase transitions, mixtures, solutions, and excess functions. Phases, phase transitions, latent heat, the Clapeyron equation, and the Gibbs phase rule are covered in Lectures 10 and 11. Lectures 12 and 13 deal with ideal and non-ideal gas mixtures and solutions. Lecture 14 provides a discussion of the concept of mixing and excess functions. Part IV, consisting of Lectures 15 through 17, covers chemical reactions and combustion. Lecture 15 deals with chemical reactions of ideal gases, the equilibrium constant, the law of mass action, the energy of formation, and the heat release from reactions. Lectures 16 and 17 cover fundamental concepts of combustion including the mass and energy balances in open and closed systems.Two appendices are included to aid the understanding of some fundamental concepts. Appendix A discusses the relationship between the macroscopic view of thermodynamics and the microscopic mechanical view and how the two are connected through statistics. Appendix B provides a clear explanation of Legendre transformations which are necessary to obtain alternate forms of the fundamental relation.Offering a concise overview of the most critical concepts of thermodynamics, the volume is ideal for those desiring a deeper understanding of the subject.