Gibbs energy
The key idea
At constant temperature and pressure, Gibbs energy provides a criterion for the direction of spontaneous change in a closed system under the usual constraints.
Why it matters
A negative ΔG indicates thermodynamic favourability for the specified change, but says nothing by itself about how fast it will happen.
A picture to remember
A negative ΔG indicates thermodynamic favourability for the specified change, but says nothing by itself about how fast it will happen.