Hydrogen has two stable isotopes ¹H and ²H (known as Deuterium)

Change in physico-chemical property: The boiling point of water consisting of

only lighter isotope of hydrogen (¹H) is 100 ⁰C but if the all the water molecules

are made of ²H, the boiling point is 101.42 ⁰C.

Reason of the change This increase in boiling point is because it is more difficult

to break bonds made out of heavier isotope. Therefore, if a water sample consisting

of molecules made of both ¹H and ²H is heated, ¹H₂O (water molecules made of ¹H)

will be more abundant in the vapor phase than in the liquid phase as compared to ²H₂O.

This change in the relative abundance of different stable isotopes is called

fractionation.

Utility of fractionation Measurement of relative amounts of the two hydrogen isotopes

in a sample can tell us about the temperature at the time of evaporation and other factors

which can influence the extent of fractionation IF we have pre-determined the affect of

different factors under the laboratory conditions.