# When seawater evaporates, the concentration of salts increases until what happens?

Apr 7, 2017

Until $\text{precipitation}$ or $\text{crystallization}$ of salts occur.........

#### Explanation:

This is an experiment you can do at home. Get some cooking salt, and some clean jars. In a separate beaker prepare a saturated solution of sodium chloride. What is a saturated solution? It is solution for which the following equilibrium occurs:

$N a C l \left(s\right) r i g h t \le f t h a r p \infty n s N a C l \left(a q\right)$

You should be able to get a mass of salt dissolved. And now decant this saturated solution into a (really) clean jar. Cap this jar loosely. Across a few weeks, as the solution slowly evaprorates, you get very LARGE macroscopic crystals of sodium chloride. I have managed to grow nuggets the size of my thumbnail.

Why should you do this? Well, (i) for fun, and (ii) it gives you an appreciation of what the phenomenon of $\text{saturation}$ is: i.e. $\text{equilibrium between dissolved and undissolved solute}$, and this leads to the definition of $\text{supersaturation}$, which is equally poorly conceived at A-level, and undergraduate level: $\text{the solution contains a concentration of solute that is greater}$
$\text{than that which contains undissolved solute.}$

For more of the same, see here and links: https://socratic.org/questions/what-is-meant-by-the-term-saturated#318172.