Classical thermodynamics is a branch of physics developed in the nineteenth century, by Sadi Carnot (1824), Emile Clapeyron (1834), Rudolf Clausius (1850), Willard Gibbs (1876), Hermann von Helmholtz (1882), and others that studied heat and work and their relation to the collision and interaction of particles in large, near-equilibrium systems.

The term classical thermodynamics is used in distinction to statistical thermodynamics, which came to be pioneered from the 1860s onwards. Statistical thermodynamics analyses thermodynamic properties by relating them to molecular-level models of microscopic behaviour in the thermodynamic system. In contrast, classical thermodynamics analyses what can be deduced solely from the macroscopic properties of the system and the laws of thermodynamics, regardless of microscopic interpretation.

Branches of

The following list gives a rough outline as to when the major branches of thermodynamics came into inception:

• Thermochemistry - 1780s
• Classical thermodynamics - 1824
• Phenomenological thermodynamics
• Chemical thermodynamics - 1876
• Statistical thermodynamics - c. 1880s
• Equilibrium thermodynamics
• Engineering thermodynamics
• Chemical engineering thermodynamics - c. 1940s
• Non-equilibrium thermodynamics - 1941
• Small systems thermodynamics - 1960s
• Biological thermodynamics - 1957
• Ecosystem thermodynamics - 1959
• Relativistic thermodynamics - 1965
• Quantum thermodynamics - 1968
• Molecular thermodynamics - 1969
• Thermoeconomics - c. 1970s
• Black hole thermodynamics - c. 1970s
• Geological thermodynamics - c. 1970s
• Biological evolution thermodynamics - 1978
• Geochemical thermodynamics - c. 1980s
• Atmospheric thermodynamics - c. 1980s
• Natural systems thermodynamics - 1990s
• Supramolecular thermodynamics - 1990s
• Earthquake thermodynamics - 2000
• Drug-receptor thermodynamics - 2001
• Pharmaceutical systems thermodynamics – 2002