Temperature Ocean Water, which is water specially prepared with a specified blend of hydrogen and oxygen isotopes. Absolute zero is defined as precisely and . It is the temperature at which all classical translational motion of the particles comprising matter ceases and they are at complete rest in the classical model. Quantum-mechanically, however, zero-point motion remains and has an associated energy, the zero-point energy. Matter is in its ground state, and contains no thermal energy. The triple point of water is defined as and . This definition serves the following purposes: it fixes the magnitude of the kelvin as being precisely
Absolute zero where "S" is the entropy. In such a circumstance, pure substances can (ideally) form perfect crystals as "T" → 0. Max Planck's strong form of the third law of thermodynamics states the entropy of a perfect crystal vanishes at absolute zero. The original Nernst "heat theorem" makes the weaker and less controversial claim that the entropy change for any isothermal process approaches zero as "T" → 0: The implication is that the entropy of a perfect crystal simply approaches a constant value. The Nernst postulate identifies the isotherm T = 0 as coincident with the adiabat S = 0, although