# Free gibbs energy doubt

I´m having serious problems with free gibbs energy equation. My main problem is that i dont know the meaning of TΔS that appears in free gibbs formula. I know that S is entropy and T temperature; but some books say that TΔS is energy lost or dispersal energy; energy unavailable to do work; but for example, lets say that the sistem loses 30 joules of heat so ΔH will be negative because it is an exothermic reaction; and lets say that the ΔS is positive at T=25°ℂ and lets say that TΔS = 30 joules. So if we add this numers in the equation -30J - 30J = -60J so this number is the energy useful to do work so this means that TΔS is also energy that is useful to do work, so my question is why some books say that this is energy unable to do work? and if you can give me a physical interpretation of TΔS ( what kind of energy is it?) i would appreciate it

## Answers and Replies

DrClaude
Mentor
Hi David, welcome to PF!

Could you please provide quotes for the statement? Just saying "some books say that" is not very helpful (sometimes, conetxt is everything).

If $\Delta S$ is positive, it usually means that heat is entering the system from the environment, which can indeed be used for additional work.