PICK UP-entropy & sencond law of thermodynamics

http://en.wikipedia.org/wiki/Entropy

entropy:
The increase in entropy is small when heat is added at high temperature and is greater when heat is added at lower temperature.

Entropy is one of the factors that determines the free energy of the system.

Macroscopic viewpoint (classical thermodynamics)
The entropy of the thermodynamic system is a measure of how far the equalization has progressed.

From a macroscopic perspective, in classical thermodynamics the entropy is interpreted simply as a state function of a thermodynamic system: that is, a property depending only on the current state of the system, independent of how that state came to be achieved.

It can be seen that the dimensions of entropy are energy divided by temperature, which is the same as the dimensions of Boltzmann's constant (kB) and heat capacity

In this manner, the quantity "ΔS" is utilized as a type of internal energy, which accounts for the effects of irreversibility, in the energy balance equation for any given system. In the Gibbs free energy equation, i.e. ΔG = ΔH - TΔS,


http://en.wikipedia.org/wiki/Second_law_of_thermodynamics

The second law of thermodynamics is an expression of the universal law of increasing entropy, stating that the entropy of an isolated system which is not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium.