Sir, could u pls tell me elaborately and theoretically what is the meaning of Gibbs Free Energy, Entropy and its physical significance..Should i refer to Peter Atkins for theoretical Thermodynamics???

Dear student,

 Gibbs free energy is a thermodynamic potential that measures the "useful" or process-initiating work obtainable from an isothermal,isobaric thermodyanamic system. Just as in mechanics, where potential energy is defined as capacity to do work, similarly different potentials have different meanings. Gibbs energy is the capacity of a system to do non-mechanical work and ΔG measures the non-mechanical work done on it. The Gibbs free energy is the maximum amount of non-expansion work that can be extracted from a closed system; this maximum can be attained only in a completely reversible process

G = H-TS

Entropy is ,thermodynamics, is a measure of the energy in a thermodynamic system not available to do useful work

ΔS = ΔQ/ΔT

Peter Atkins is a good book, you can refer to it