# 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.

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.

• Were you referring to Gibs free energy or Helmholtz? @user41006 If you you were referring to Helmholtz then its the same idea except with internal energy and not enthalpy. Commented Feb 25, 2014 at 9:45
• can a permanent magnet be exploited to get energy that can be used to do useful work without using any other energy..if this is possible then there must be some free energy may be helmholtz..and are permanent magnets permanent ..or they lose their property very slowly? Commented Feb 25, 2014 at 10:12
• @user41006 You can never get useful work out without putting work in somehow to the system i.e. superconductors must be cooled (lots of energy required) to get resistance free current. Permanent magnets are permanent for temeperatures below some point ( depends on material). They dont lose their magnetism if they are left alone. Magnetism comes from electron properties which are quantized and can never go to zero for individual electrons, only on average for group of electrons. Commented Feb 25, 2014 at 10:32

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 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.