Thermodynamics is the branch of physics and chemistry related to the thermal behaviour of bodies, the study of energy and its transformations (in particular, internal energy).
Thermodynamics. Thermodynamics is the study of the transformations of systems (collections of bodies that may or may not be separated by a material barrier), open or closed (according to whether or not matter is exchanged with the exterior), isolated or not (according to whether or not energy is exchanged with the exterior) represented by variables of state (intensive or extensive).
The basic theoretical notions of thermodynamics are heat, thermodynamic temperature, internal energy, enthalpy, entropy and reversibility.
The experimental values are heat capacities, pressure, volume etc.
The main laws of thermodynamics are the first principle, the second principle (V. Carnot, Clausius) and the third principle (V. Nernst) of thermodynamics.
The study of the thermodynamics of bodies includes the design and validation of models for the thermal behaviour of bodies, equations of state, established using experimental values. In practice, the equilibria predicted by thermodynamics can be contradicted by the influence of time (reaching thermodynamic equilibrium can sometimes take an infinite time) and are governed by kinetics (cf. Arrhenius). In chemistry, thermodynamic equilibrium is governed by the law of mass action (V. Guldberg).