The study of energy transformations is the subject matter of thermodynamics. Various forms of energy are interrelated and under certain conditions, these may be transformed from one form into another. In a chemical reactions, energy stored by molecules can be released as heat. The chemical energy may also be used to do mechanical work when a fuel burns in an engine. The laws of thermodynamics can be applied with energy changes of macroscopic systems involving a large number of molecules rather than microscopic systems containing a few molecules. More over thermodynamics is not concerned about how and at what rate these energy transformations are carried out, but is based on initial and final states of a system undergoing the change.

`text(Objectives and limitations of thermodynamics)` :

`text(Objectives)` :
(i) Interrelate various energy changes during physical or chemical transformation.
(ii) Predict the feasibility of given change.
(iii) Deduce various laws, e.g. phase rule, distribution law, law of mass action etc. thermodynamically.
(iv) Derive at what conditions, the equilibrium is attained by a change.

`text(Limitations)` :
(i) It's laws are valid for bulk of matter and does not provide information about individual atom.
(ii) It predicts feasibility of reaction but fails to suggest rate of reaction.
(iii) It fails to explain the systems which are not in equilibrium.