Examples of State Functions in Thermodynamics

State functions are crucial in thermodynamics as they provide a way to describe and analyze systems without having to consider the specific process that occurred. Here are some important state function examples commonly considered in thermodynamics:

• Temperature
• Pressure
• Volume
• Internal Energy
• Gibb’s Free Energy
• Entropy
• Enthalpy

Temperature (T)

Temperature is a measure of the average kinetic energy of the particles in a system. It is a state function because it describes the current state of the system, irrespective of the path taken to reach that state.

Pressure (P)

Pressure is the force applied per unit area on a surface. It is a state function as it only depends on the current state of the system. Pressure is an essential parameter to determine the behavior of gases and fluids in various thermodynamic processes.

Volume (V)

Volume refers to the amount of space occupied by a substance or system. In thermodynamics, volume is an essential parameter in determining the behaviors of gases and fluids, especially in processes involving expansion or compression.

Internal Energy(U)

Internal energy represents the total energy stored within a system, surrounding the kinetic and potential energies of its particles. Internal energy is crucial in understanding the energy transfers and changes within a system during various thermodynamic processes.

The Internal Energy is given by the following equation:

ΔU=Q-W

where ΔU represents the change in internal energy, Q is the heat added to the system, and W is the work done by the system.

Enthalpy(H)

Enthalpy is the total heat content of a system at constant pressure. It includes the internal energy of the system and the work required to move the system’s surroundings.

Enthalpy is a state function as it depends only on the current state of the system, regardless of the path taken to achieve that state. It is particularly useful in studying heat transfer processes and chemical reactions.

The Enthalpy is given by the following equation:

ΔH = ΔU + PΔV

where ΔV represents the change in volume and P is the pressure.

Entropy(S)

Entropy is a measure of the disorder or haphazardness within a system. It is a state function as it depends only on the current state of the system, irrespective of the path taken to achieve that state.

Entropy provides valuable information about the direction and extent of spontaneous processes and is a fundamental concept in understanding thermodynamic equilibrium.

Gibbs Free Energy(G)

The Gibbs free energy, denoted by the symbol “G,” predicts whether a chemical or physical process will occur spontaneously at constant temperature and pressure. It combines enthalpy, entropy, and temperature into a single equation. If the Gibbs free energy is negative, the process is spontaneous, indicating that the system tends to move towards a lower energy state.

Gibbs free energy is a state function as it depends only on the current state of the system, regardless of the path taken to achieve that state.

It is commonly used in chemical reactions and phase transitions to predict the possibility and direction of such processes.
The Gibb’s Free Energy is given by the following equation:

ΔG = ΔH – TΔS

where ΔS refer to the change in entropy and T is the temperature.

State Functions are the functions that are independent of the path of the function i.e. they are concerned about the final state and not how the state is achieved. State Functions are most used in thermodynamics. In this article, we will learn the definition of state function, what are the state functions in Thermodynamics, and how they differ from path function.