**Laws of Thermodynamics** __Zeroth law__ The zeroth law underlies the definition of temperature.

*If two thermodynamic systems are each in thermal equilibrium with a third, then they are in thermal equilibrium with each other.* __First law__ The first law mandates conservation of energy and states in particular that heat is a form of energy.

*Energy can neither be created nor destroyed. It can only change forms.* __Second law__ The second law states that the entropy of the universe always increases

*dE = T dS - p dV* where:

E is the internal energy, T is temperature, S is entropy, p is pressure and V is volume.

The first law in words: The net change of internal energy dE equals the inflow of energy that flows in T dS minus the outflow of energy when the system performs work ( p dV)

__Third law__ The third law concerns the entropy of an object at absolute zero temperature, and implies that it is impossible to cool a system all the way to exactly absolute zero.

*As temperature approaches absolute zero, the entropy of a system approaches a constant minimum.* __References:__ http://en.wikipedia.org/wiki/Laws_of_thermodynamics