Microscopic modes of energy

The microscopic modes of energy refer to the energy stored in the molecular and atomic structure of the system.

The molecules are in random motion. A molecule possesses energy in several forms.

• Translational energy, Rotational energy, Vibrational energy.
• Electronic energy, Chemical energy, Nuclear energy.

If ε represents energy of one molecule, then

If N is the total number of molecules in the system, then the total amount of microscopic form of energy

We may also call this as INTERNAL ENERGY of the system. The internal energy, U is due to random motions or disorganized motions of molecules. The internal energy cannot be readily converted into work. One of the major tasks involved in thermodynamics is devising means for converting disorganized internal energy into useful or organized work.