1. The problem statement, all variables and given/known data Hi all. Lets take a look at the Helmholtz free energy. It is defined as the amount of energy one has to put in to create a system once the spontaneous energy transfer to the sytem from the environment is accounted for. Now lets look at it once we have created the system. Now F = U - TS is the energy we get from annihilating system. Why is it we have to subtract TS? Is it because we are talking about reversible processes, or what? Thansk in advance.