As a science, thermodynamics was formulated in the 18th and 19th centuries. At that time it concentrated on investigating the transformation of different forms of energy. Thermodynamics was then formulated as a science about temperature, heat, and also interconvertibility of heat and work into each other. The term was derived from the Greek "terme" (heat), and "dynamics", (force, power, or work).
The history of thermodynamics started with G. Galilei (1597) who introduced the concept of temperature and invented one of the first thermometers. It was G. Black (1770) who was the first to use the term "thermodynamics". In 1772 G. Wilke introduced the unit of measuring the amount of heat, a calorie. It was W. Thompson (1854) who introduced the term "thermodynamics" into conventional use.
With expansion of the knowledge base in this field, thermodynamics started to include specialty areas, and accordingly the subject of thermodynamics as a science has become formulated in various topics listed below.
- In the 20th century, thermodynamics became a basic independent division of Theoretical Physics dealing with the study of general properties of physical systems under equilibrium, as well as common regularities taking place while attaining equilibrium. Thermodynamics is divided into phenomenological and statistical thermodynamics.
- Phenomenological (classical) Thermodynamics proceeds from experimentally established principles and operates with the recognized data on the properties of physical bodies.
- Statistical Thermodynamics is based on representations of the molecular (atomic) structure of physical bodies. Its tools are statistical methods and the mathematical apparatus of probability theory.
- Non-equilibrium Thermodynamics. The first considerations of thermodynamic analysis of non-equilibrium processes were proposed by W. Thompson in 1854; however, it was developed as a separate branch of science only in the 20th century based on the works of G. Meissner, I. Prigogine, and S. DeGroot. Non-equilibrium thermodynamics focuses on studying processes in their development not having yet reached equilibrium, and on the quantitative study of non-equilibrium processes—in particular the rate of the processes as dependent on the ambient conditions, and of the direction of said processes.
- The Axiomatic method of Thermodynamics, devised by a Greek theoretical physicist S. Caratheodory (1909), makes it possible to derive all the postulates of thermodynamics from several initial axioms.
- Chemical Thermodynamics studies the dependence of thermodynamic properties of substances on their composition, structure, and existence conditions. The objects of its study are chemical reactions, heat absorption and heat release processes taking place at chemical reactions (Thermochemistry), the rate of chemical reactions (Chemical Kinetics), first- and second-order Phase Transitions, Adsorption and Absorption, chemical and physical equilibrium, Solutions, and Electrochemical processes.
- Engineering Thermodynamics, which developed as an area of specialty within the engineering field in the 20th century, deals with the interrelationship between heat and work. The object of its study is the use of the Laws of thermodynamics in engineering of thermal processes, namely, developing the theory of heat engines and plants; investigating into the process of transforming heat energy into mechanical or electrical power; analyzing thermodynamic cycles as applied to power plants and heat power plants; designing refrigeration plants and gas liquefaction plants; and investigating the processes of heat exchange and the heat engineering properties of substances.