Kinetic fractionation is a process that separates stable isotopes from each other by their mass. It is a unidirectional process. Isotopes are forms of an element whose nuclei have the same atomic number–-the number of protons in the nucleus--but different atomic masses because the contain different numbers of neutrons. ...

One naturally-occuring example of kinetic fractionation is the evaporation of seawater to form clouds. In this instance, isotopically-lighter water molecules (i.e., those with ¹⁶O) will evaporate slightly more easily than will the isotopically-heavier water molecules with ¹⁸O. Sea water is water from a sea or ocean. ... Cumulus of fair weather A cloud is a visible mass of condensation droplets or ice crystals suspended in the atmosphere above the surface of the Earth or another planetary body. ... Water (from the Old English word wæter; c. ... General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ... General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ...

During the course of this process the oxygen isotopes are fractionated: the clouds become enriched with ¹⁶O, the seawater becomes enriched in ¹⁸O. Thus, rainwater is observed to be isotopically lighter than seawater. Fractional distillation is the separation of a mixture of compounds by their boiling point, by heating to high enough temperatures. ...