How does salinity affect the density of water?

1 Answer
Nov 18, 2015


If you know that dissolution of salt only marginally affects the volume of the solution, how would you expect the density to evolve? It should reasonably increase.


The density of pure water is #1.00# #g*cm^-3# at a given temperature. Should salts be dissolved in the water, and the volume remains reasonably constant, the density of the solution should markedly increase from #1.00# #g*cm^-3#. A solute binds water molecules around itself in a coordination sphere, and should a salt be dissolved, both anion and cation must be solvated; hence an increase in solution density with respect to water.

Just wanted to add that because the density of salt water is greater, a body (a swimmer!) is far more buoyant in sea water than in fresh water. Why should this be so?