The sign of theGibbs free energy, ΔG, determines whether a process will occur spontaneously or not. A process with a negative ΔG value will be spontaneous.

Some chemical processes may be spontaneous only above or below a certain temperature, whereas other processes are always spontaneous or never spontaneous. Since the Gibbs free energy is calculated by the equation ΔG = ΔH - TΔS, when the temperature is zero ΔG = ΔH, and the spontaneous reactions are the exothermic ones.

You can read some examples of reactions that are only spontaneous above or below a certain temperature在这里

You can read some examples of reactions that are always or never spontaneous在这里