Thermodynamics Glossary

A thermodynamic process in which no heat is exchanged between the system and its surroundings ($Q = 0$).

A theoretical thermodynamic cycle consisting of two isothermal and two adiabatic processes. It represents the most efficient possible engine between two temperatures.

A measure of the effectiveness of a refrigerator or heat pump: $\text{COP}_{\text{ref}} = Q_C / W$ for a refrigerator.

Heat transfer through direct molecular collisions within a material, driven by a temperature gradient.

Heat transfer by the bulk movement of a fluid (liquid or gas) due to temperature-driven density differences.

A measure of the number of microstates consistent with a given macrostate; quantifies the dispersal of energy. Symbol: $S$, units: J/K.

A device that converts thermal energy into mechanical work by operating between a hot and cold reservoir in a cyclic process.

The total kinetic and potential energy of all molecules in a system. For an ideal gas, it depends only on temperature.

A thermodynamic process occurring at constant pressure.

A thermodynamic process occurring at constant volume; also called isometric or isovolumetric.

A thermodynamic process occurring at constant temperature.

A graph plotting pressure vs. volume for a gas. The area under a process curve represents work; the area enclosed by a cycle represents net work.

Heat transfer via electromagnetic waves; the only mechanism that can operate through a vacuum.

The amount of heat required to raise the temperature of 1 kg of a substance by 1 K. Symbol: $c$, units: J/(kg K).

The state in which two systems in thermal contact no longer exchange net heat because they are at the same temperature.

The branch of physics dealing with heat, work, temperature, and energy, and the laws governing their interconversion.