Thermodynamics is a branch of physics concerned with heat and temperature and their relation to energy and work. It defines macroscopic variables, such as internal energy, entropy, and pressure, that partly describe a body of matter or radiation. It states that the behavior of those variables is subject to general constraints, that are common to all materials, not the peculiar properties of particular materials. These general constraints are expressed in the four laws of thermodynamics. Thermodynamics describes the bulk behavior of the body, not the microscopic behaviors of the very large numbers of its microscopic constituents, such as molecules. The basic results of thermodynamics rely on the existence of idealized states of thermodynamic equilibrium. Its laws are explained by statistical mechanics, in terms of the microscopic constituents.

Thermodynamics applies to a wide variety of topics in science and engineering, especially physical chemistry, chemical engineering and mechanical engineering.

 Topical Notes, Topical Notes, Problems, Presentations, Quiz, Test, Investigations and Videos              
Kinetic Theory of gases 
Ideal Gases
Temperature and the Zeroth Law of Thermodynamics                
First Law of Thermodynamics 
Thermodynamic Process and PV diagrams
Reversible and Irreversible Processes
Heat Engines
Heat Pumps and Refrigerators
Carnot Cycle
Second Law of Thermodynamics
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Historically, the distinction between heat and temperature was studied in the 1750 s by Joseph Black. Characteristically thermodynamic thinking began in the work of Carnot (1824) who believed that the efficiency of heat engines was the key that could help France win the Napoleonic Wars. The Irish-born British physicist Lord Kelvin was the first to formulate a concise definition of thermodynamics in 1854:

“Thermo-dynamics is the subject of the relation of heat to forces acting between contiguous parts of bodies, and the relation of heat to electrical agency.”