3Internal energy
Internal energy is the sum of all microscopic forms of energy of a system. It is related to the molecular structure and the degree of molecular activity and may be viewed as the sum of kinetic and potential energies of the molecules; it comprises the following types of energy:
Type Composition of internal energy (U)
Sensible energy-- the portion of the internal energy of a system associated with kinetic energies (molecular translation, rotation, and vibration; electron translation and spin; and nuclear spin) of the molecules.
Latent energy -- the internal energy associated with the phase of a system.
Chemical energy - the internal energy associated with the different kinds of aggregation of atoms in matter.
Nuclear energy - the tremendous amount of energy associated with the strong -bonds within the nucleus of the atom itself.
Energy interactions -- those types of energies that are not stored in the system (e.g. heat transfer, mass transfer, and work), but are recognized at the system boundary as they cross it, representing gains or losses by a system during a process.
Thermal energy -- the sum of sensible and latent forms of internal energy.
