THIRD LAW OF THERMODYNAMICSThere are several methods to state the third law of thermodynamics, one of the definitions more directly applicable to the chemical thermodynamics is the one formulated by Lewis and Randall " if the entropy of every element in a crystalline perfect state is considered to be zero a 0 K, then the entropy of any perfect crystalline substance is also zero to K S for any isothermal process is zero to 0 K ".This third principle or third law is a result of experimentation in the thermal regime near to the absolute zero and it has not been violated yet consequently, it is considered to be a "law". From a practical point of view it states that it is impossible to reach the temperature of the absolute zero with a process that is not reversible, because near the point zero, the change of entropy is zero, and the only irreversible way of lowering the entropy is to have an environment colder than the absolute zero and this is impossible for the final approximation to the absolute zero, in the cooling of any material must be reversible and an adiabatic (isentropic).A T = 0. All the energy of the thermal movement has extinguished, and in a perfect crystal every atoms or ions are in a regular and uniform order. The arrangement of matter and the absence of thermal movement suggest that this kind of materials also have entropy equal to 0. This conclusion is related to the molecular interpretation of entropy, because S=0 if there is one unique way of arrangement for the molecules and only it is in an accessible microstate (basal state)Nernst heat theoremThe experimental observation that turns out to be consistent with the view that the entropy of a regular array of molecules is zero at T=0, is summarized by the Nernst heat theorem:The entropy change accompanying any physical or chemical transformation approaches 0 as the temperature is approaches 0: S= 0 when T= 0, provided that all the substance involved are perfectly ordered.