Thermodynamics Vocabulary

Flashcards covering key vocabulary from a Thermodynamics lecture.

Thermodynamics

The branch of physics that deals with the concepts of heat and temperature and the inter-conversion of heat and other forms of energy. It is a macroscopic science dealing with bulk systems.

Thermal Equilibrium

A state where the macroscopic variables that characterise the system do not change in time.

Adiabatic Wall

An insulating wall that does not allow flow of energy (heat) from one system to another.

Diathermic Wall

A conducting wall that allows energy flow (heat) from one system to another.

Zeroth Law of Thermodynamics

Two systems in thermal equilibrium with a third system separately are in thermal equilibrium with each other.

Temperature (T)

The thermodynamic variable whose value is equal for two systems in thermal equilibrium.

Internal Energy (U)

The sum of the kinetic and potential energies of all molecules within a system, in the frame of reference relative to which the center of mass of the system is at rest. It is a state variable.

Heat

Energy in transit due to temperature difference. It is a mode of energy transfer and not a state variable.

Work

A mode of energy transfer to a system resulting in a change in its internal energy. It is not a state variable.

First Law of Thermodynamics

∆Q = ∆U + ∆W, where ∆Q is heat supplied to the system, ∆U is the change in internal energy, and ∆W is the work done by the system.

Specific Heat Capacity (s)

s = (1/m) * (∆Q/∆T), where m is the mass of the substance, ∆Q is the heat supplied, and ∆T is the change in temperature.

Molar Specific Heat Capacity (C)

C = (1/µ) * (∆Q/∆T), where µ is the number of moles of the substance, ∆Q is the heat supplied, and ∆T is the change in temperature.

Isothermal Process

A process in which the temperature of the system is kept fixed throughout.

Adiabatic Process

A process in which the system is insulated from the surroundings and no heat flows between the system and the surroundings.

Isochoric Process

A process in which the volume is constant.

Isobaric Process

A process in which the pressure is constant.

Cyclic Process

A process in which the system returns to its initial state.

Second Law of Thermodynamics

Kelvin-Planck statement: No process is possible whose sole result is the absorption of heat from a reservoir and the complete conversion of the heat into work. Clausius statement: No process is possible whose sole result is the transfer of heat from a colder object to a hotter object.

Reversible Process

A thermodynamic process that can be turned back such that both the system and the surroundings return to their original states, with no other change anywhere else in the universe.

Irreversible Process

A spontaneous process of nature that cannot be reversed.

Carnot Engine

A reversible engine operating between two temperatures, consisting of two isothermal processes connected by two adiabatic processes.

Quasi-static process

An idealised process in which at every stage the system is in an equilibrium state.