The measurement of thermal energy involves indirect measurement of the molecular kinetic energies of a substance. Rather than providing an absolute measure of molecular kinetic energy, thermal measurements are designed to determine differences that result from work done on, or by, a substance (e.g., heat added to, or removed from, a substance). Temperature differences correspond to changes in thermal energy states and there are several analytical methods used to measure differences in thermal energy via measurement of temperature.

When dealing with the terminology associated with the measurement of thermal energy, one must be mindful that there is no actual substance termed "energy" and no actual substance termed "heat." Accordingly, when speaking of energy "transfer" or heat "flow", one is actually referring to changes in functions of state that can be raised or lowered only within a body or system. Neither energy...