Free Energy and Spontaneity of Systems Every process that occurs all around us can be divided into two sections: spontaneous and non-spontaneous. There have been many theories to describe the spontaneity of a system and the dependence of the system spontaneity on a certain variable. Such variables are being the change of enthalpy of the system (ΔH), the change of entropy of the system (ΔS) and finally the explanation was given by regarding about the ‘free energy’. Everything in the universe is made out of the inter-conversion of energy and mass. Energies are concentrated in masses. If we observe a chemical reaction we can see that there is some amount of energy trapped as ‘the bond energy’. When we break a bond or make a bond or when the system does work or work is done on the system we can observe the evolution of some energy or loss of some energy regarding these processes. ‘Free energy’ means that the energy is not bound anymore. It’s fre...