Key Idea : State function is the property of the system whose value depends only on the initial and final state of the system and is independent of the path. ∵ Internal energy (ΔE)=q+W It is a state function because it is independent of the path. It is an extensive property. ∵ Gibbs energy (G)=H−TS It is also a state function because it is independent of the path. It is also an extensive property. Heat (q) and work (W) are not state functions being path dependent.