The internal energy of a substance, associated with
the positions and motions of its component molecules,
atoms, and ions.
The average kinetic energy of the
molecules or atoms, which is due to their motions,
is measured by the Temperature of the substance. The
potential energy is associated with the state, or
phase, of the substance (states of matter).
is commonly expressed in Calories, British Thermal
Units, or Joules.
Heat may be transferred from one
substance to another by three means Conduction, Convection,