Is Internal Energy a State Function?

Yes — internal energy is a state function in thermodynamics.

A state function is a property that depends only on the current state of the system (defined by parameters like temperature, pressure, and volume), not on the path taken to reach that state.

Since internal energy represents the total energy (kinetic + potential) of particles in a system, its value is determined solely by the system’s current state.

Also Check: What is the Internal Energy Reserve in Plants and Animals?

Why Internal Energy is a State Function

1. Path Independence – The change in internal energy (ΔU) between two states depends only on the initial and final conditions, not on the process or pathway.
   • Example: Whether you heat water slowly or rapidly, the change in internal energy depends only on its starting and ending temperature.
2. Thermodynamic Basis – According to the First Law of Thermodynamics:
3. ΔU=q+w
4. ΔU=q+w
5. where q is heat added and w is work done.
   • While heat (q) and work (w) depend on the path, their sum (ΔU) is fixed for given initial and final states → making internal energy a state function.
6. Microscopic Definition – Internal energy is the sum of microscopic motions and interactions of molecules, which are uniquely defined at a given state.

Also Check: What is the Internal Energy Reserve in Plants and Animals?