This Thermodynamics book is designed to help students understand the fundamental concepts of energy, heat, and changes in chemical systems. The material is presented in a gradual and structured manner, with an emphasis on conceptual understanding and physical meaning rather than complex mathematical approaches. The discussion begins with gas systems as a foundation to introduce key concepts such as pressure, temperature, work, and equations of state, followed by the laws of thermodynamics and concepts including internal energy, enthalpy, entropy, and free energy. The relationship between thermodynamics and chemical equilibrium is also explored to explain the direction and conditions of chemical changes. Equipped with examples, diagrams, summaries, and exercises, this book aims to build a strong foundation for further study in chemistry.