Temperature dependence of the free energy change

It is apparent that ΔG depends on the temperature in Kelvin from the relationship below that defines the free energy change in terms of the enthalpy and entropy changes of the system .


The direction in which ΔG changes with temperature depends on the sign of ΔS because
 

• if ΔS is positive,
  the –TΔS contribution to ΔG is negative and
  ΔG becomes more negative at higher T
• if ΔS is negative,
  the –TΔS term is positive
  and ΔG becomes more positive at higher T

Because for reactions involving gases, it is often possible to predict the sign of ΔS, for these same reactions it is also possible to predict how ΔG changes with temperature.