termodinamic

Thermodynamics, often rendered as termodinamic in some languages, is a branch of physics that studies how heat and energy interact with matter. It examines how energy is transformed between different forms, how heat flows between a system and its surroundings, and how macroscopic properties such as temperature, pressure, and volume change. A thermodynamic description uses state variables that describe the condition of a system.

The subject is organized around four foundational concepts. The Zeroth Law states that if two systems are separately in thermal equilibrium with a third, they are in equilibrium with each other, allowing the definition of temperature. The First Law expresses energy conservation: for any process, the change in internal energy equals the heat added minus the work done. The Second Law introduces entropy and sets a direction for natural processes, limiting the efficiency of heat engines and explaining irreversible behavior. The Third Law states that the entropy of a perfect crystal approaches zero as temperature approaches absolute zero.

Thermodynamics encompasses classical or macroscopic thermodynamics, statistical thermodynamics (which derives macroscopic properties from microscopic behavior), and chemical thermodynamics focused on chemical reactions and phase changes. Core concepts include enthalpy, entropy, Gibbs free energy, and phase equilibria. Applications span engines and power cycles, refrigeration, phase transitions, calorimetry, materials science, and energy and environmental analysis, reflecting its central role in science and engineering.