free energy and entropy my understanding of free energy and entropy is that as entropy of a system increases its free energy decreases. As sun has free energy and this energy is being converted to useful work, and its entropy is increasing. Its entropy will continue to increase till its material is exhausted to cease free energy production. 
Can permanent magnets be a source of free energy? The question arises because  magnets are permanent dipoles  that lose their orientation very slowly to become disordered and increase its entropy.
 A: I would comment this but I have no rep points. Here is a link that will explain it: http://2ndlaw.oxy.edu/gibbs.html 
The main point is that free energy also is dependent on enthalpy, not just entropy.
A: So a large increase in entropy would decrease the activation energy. Together with the change in enthalpy, they decide the spontaneity of the reaction. If the expression for the Gibbs free energy is negative at a given temperature, the reaction is spontaneous, meaning that it occurs.
A: A large entropy is beneficial to a system, in that it lowers the total energy of the system. So a large increase in entropy would decrease the activation energy. Together with the change in enthalpy, they decide the spontaneity of the reaction. If the expression for the Gibbs free energy is negative at a given temperature, the reaction is spontaneous, meaning that it occurs.
However, just because a reaction occurs, it doesn't mean that the reaction is significantly noticeable. The conformational change of diamond to graphite has a negative ΔG, but I have yet to see any diamonds turn to carbon. This is because the reaction rate is so slow, that it would take forever (in our perspective) to see it happen.
