Lowest possible temperature, according to the kinetic theory of gases, attained when a Definable part of the universe that can be open, closed, or isolated. An open system exchanges both matter and energy with its surroundings. A closed system can only exchange energy with its surroundings; it has walls through which heat can pass. An isolated system cannot exchange energy or matter with is at its minimum possible energy, equal to 0 K (-273.15° C and -459.67 F). Temperature is a reflection of molecular energy, thus there must be a point at which no further energy can be extracted from a system. Although it is possible to approach absolute zero, the “third law” of thermodynamics holds that it is impossible to attain absolute zero in a system.
Some or all content above used with permission from J. H. Wittke.