What are meant by the terms change of entropy `(DeltaS)` and change in free energy `(DeltaG)` of a system. Write down the mathematical relation between them. At `0^(@)C`, liqiud water and ice remain in equilibrium. If 1 g of liquid water under equilibrium condition is converted to ice, explain with reason whether the process is endothermic or exothermic .

Explanation

First and second part:
Third part: in the conversion of water into ice, the entropy of the systemm decreases, and hence `DeltaS_("sys")lt0`.
We know, `DeltaG=DeltaH-TDeltaS` . . .[1]
For the given process, `DeltaS lt0`. As the process occurs spontaneously, `DeltaG lt0` for the process. according to the relation [1], if `DeltaS lt0`, then `DeltaG` will be negative only when `DeltaH lt0`. so, the process is exothermic.