It is an important thermodynamics property of a working substance, which increases with the additional of heat, and decreases with its removal. As a matter of fact, it is tedious to define the entropy. But it is comparatively easy to define change of entropy of a working substance. Over small range of temperature, da increase decrease of entropy, when X the absolute temperature, gives the heat absorb or rejected by the working substance. Mathematically heat absorbed or rejected by the working substance,…..
dQ = T ds
where,. T = Absolute Temperature
ds = increase or decrease in entropy.
Theoretically, the entropy of a substance is zero at absolute zero temperature. Hence, in entropy calculation, some convenient data should be selected from which measurement may be made.
Be noted that the where at 0° C is assumed to have zero entropy. And changes in its entropy are reknocked from this temperature.