Question

How does salinity affect the density of water?

Answer 1

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.

Explanation:

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?