involves energy on the microscopic scale
. It may be divided into microscopic potential energy, Upot
, and microscopic kinetic energy, Ukin
U = Upot + Ukin
where the microscopic kinetic energy, Ukin, involves the motions of all the system’s particles with respect to the center-of-mass frame. For an ideal monatomic gas, this is just the translational kinetic energy of the linear motion of the atoms. Monoatomic particles do not rotate or vibrate. The behavior of the system is well described by kinetic theory of gases. Kinetic theory is based on the fact that during an elastic collision between a molecule with high kinetic energy and one with low kinetic energy, part of energy will transfer to the molecule of lower kinetic energy. However, for polyatomic gases there isrotational and vibrational kinetic energy as well.
The microscopic potential energy, Upot, involves the chemical bonds between the atoms that make up the molecules, binding forces in the nucleus and also the physical force fields within the system (e.g. electric or magnetic fields).
In liquids and solids there is significant component of potential energy associated with the intermolecular attractive forces.