Table of Contents
State functions, often known as point functions, are attributes whose value is independent of the path taken to arrive at that value. Path functions, on the other hand, are those functions that do depend on the path between two points. State functions are values that change depending on the state of a substance, such as a temperature, pressure, or the amount or type of substance. In fact, state functions are unaffected by how the state was reached or established. Density, for example, is a state function because the density of a substance is unaffected by how it is obtained. Keep this rule in mind when determining whether a property is a state function or not: is this property or value affected by the path or way taken to establish it? If the answer is yes, the property is not a state function; otherwise, the property is a state function. Integrals can be used to describe state functions. This is due to the fact that integrals are only dependent on three things: the function, its lower limit, and its upper limit. Similarly, state functions are determined by three factors: the property, the initial value, and the final value. As a result, it is clear that state functions are only affected by the property’s initial and final values. The integral of enthalpy H, for example, is given by, where t0 represents the initial state and t1 represents the final state.
This equation is similar to the enthalpy equation, which is:
ΔH = Hfinal − Hinitial
State Functions List
Pressure: Pressure is a measure of the average force exerted on the container walls by the constituent molecules per unit area. Pressure is a state function because it is independent of the path of the molecules.
Temperature: Temperature is defined as the average kinetic energy of the system’s atoms or molecules. Temperature is a state function because it measures the property of a system’s state regardless of how it got there.
Volume is the amount of physical space occupied by a substance and is independent of the path taken. As a result, the volume is a state function.
Mass is a measure of the amount of matter in an object that is usually measured in grammes (g) or kilogrammes (kg). Mass is a state function that measures the quantity of matter regardless of its location in the universe or the gravitational force acting on it.
Internal energy is defined as the total amount of energy associated with molecular motions. The internal energy of ideal gases is determined solely by temperature (Joule’s law), whereas the internal energy of real gases is determined by temperature, pressure, and volume (temperature and volume being the dominating quantities and effect of pressure are negligible).
Gibb’s free energy is defined as the enthalpy of the system at any point minus the product of the temperature times the entropy of the system. G is equal to H – TS. Because it is defined in terms of thermodynamic properties that are state functions, the system’s Gibbs free energy is a state function.
Entropy: Entropy is a measure of system imbalance that is completely independent of the path the system took to achieve that state and is unique to the current state of the system.
Also read: Hydrogen As A Fuel
FAQs
What kinds of state functions are there?
Density, internal energy, enthalpy, and entropy are examples of state functions. Such a relation cannot be written for path functions, particularly because they cannot be defined for the limiting states. Path functions are determined by the path taken between two states. Heat and work are two examples of path functions.
What does not constitute a state function?
Work and heat are not state functions. Work cannot be a state function because it is proportional to the distance moved by an object, which is determined by the path taken to get from the initial to the final state. Heat cannot be a state function if work is not a state function.
