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What's a state function in chemistry?

What's a state function in chemistry, Thermodynamics?

 

"If you don't rely on the path – it's a STATE FUNCTION."

State function A state function is a property whose value does not depend on the path taken


State functions depend on three things: the property, the initial value, and the final value.

What are state function properties? The term "state function" sounds scary but it merely refers to properties of matter such as temperature, pressure, volume, mass, moles, etc. Matter exists in different states (solid, liquid or gas) and these properties play an important part in how matter behaves changine from one state to another.

State function properties don't depend on the path. For example freezing water. It doesn't matter if you

  • a) first cool the water down by refrigerating it or
  • b) you simply put the water straight into the freezer from the tap.

Going from (a) to (b), liquid state to solid state, the change in temperature of the water is the same for either path.

Equilibrium is reached when a static condition is reached, it means no tendency toward change. So, once the water has become ice, it doesn't undergo any more changes and has reached its final state.

Change in state function

To determine the change in any state function, you subtract the initial value from the final value.

Example, to determine the change in a state function, temperature,  ΔT = ΔT(final) – ΔT(initial)

State functions are commonly used in thermodynamics. For example calculating the change in enthalpy or entropy in a system. State functions are crucial in thermodynamics because they make calculations simple and enables one to calculate values that otherwise could only be obtained through experiments.

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