GIBBS FREE ENERGY FUNCTION

Introduction to thermodynamics
A dictionary defines thermodynamics as"the science of the relations between heat and mechanical work",but it might more usefully be defined as the study of the changes in energy accompanying chemical and physical changes,which allows experimentally determined laws to be derived from certain basic principles,and helps to predict changes which have not been observed.It must be remembered that thermodynamics considers only the initial and final states of any system under going a change,and provides no information about the mechanism of the change between these states,or the rate at which the change takes place-this is the subject of reaction kinetics(where the change taking place is a chemical reaction).
The First Law of Thermodynamics.
This is a law based on experience,and is an extension of the principle of conservation of Energy wich states that energy cannot be created or destroyed,provided that ther is no measurable conversion of mass to energy:it can only be converted from one form to another.The consistency of Joules mechanical equivalent of heat is explained by this principle,and it is clear that if it obeyed,no machine can be devised which will do work without the expenditure of an equivalent amount of energy.In order to metal a given mass of ametal,acertain ammount of energy must be supplied-whether by combustion of afuel or the expenditure of electrical energy.