## State Function and State Variable. State.
"The condition of a system is called the state of a system". A thermodynamic state is a macroscopic condition of a system for which its properties are uniquely determined and are independent of time.
Explanation.
We perform experiments on a system to measure its properties, which completely define the state of a system at a particular moment. For example, composition, pressure, volume, temperature, and mass. A system is in a definite state when each of its properties has a definite value. This defines the system completely. In thermodynamics, initial and final states and noted, to determine the change in a property.
State Function and State Variable.
"A property that depends upon the state of a system is called state function". It is independent of the path by which the state has reached. For example, enthalpy, free energy, entropy, internal energy, volume, temperature, and pressure. Change in state function is also a state function. For example, internal energy E of a system is a state function. The change in E depends on the initial and final states of the system. Thus

ΔE  = Efinal   -  Einitial

and ΔE is also a state function because it is not a path-dependent property.

### Modular Representation of a State Function.

Consider that you want to reach the top of the mountain. The two paths are : (a) which is short but
steep and the path (b) which is longer and more gradual. The time taken to climb is different but the height to be covered is same in this adventure. the height corresponds to a state function.

### Characteristics of a State Function.

1. The change in state function depends on the initial and final states of the system. It is independent of the path of reaction.
2. The change in the state function is also a state function.
3. State functions for a system are not generally independent of each other.
4. For any particular state of a system, state function has a unique value. For example, at a particular state, a system has a unique value of internal energy E.
5. In cyclic process, change in state function is zero.
State Function | State & Explanation, State Variable | Reviewed by Genuine Chemistry on August 31, 2019 Rating: 5