Dilution and separation.

Step 1 of 6

A sample

A solution is uniform: its concentration is the same everywhere in it. So if you take a sample of it, with a spoon or a pipette, the sample has the same concentration as the whole solution, even though it holds less solute.

Step 2 of 6

Dilution

Diluting means adding solvent to a solution. The moles of solute do not change, but they spread through a bigger volume, so the concentration falls. Since $n = cV$⁠ stays the same,

$c_1 V_1 = c_2 V_2$⁠

Step 3 of 6

How much water

The same equation tells you what volume to dilute to: $V_2 = \dfrac{c_1 V_1}{c_2}$$V_2 =$$\dfrac{c_1 V_1}{c_2}$⁠. The water you add is $V_2 - V_1$⁠.

Step 4 of 6

Filtering

A mixture can be taken apart again, because each part keeps its own properties. Filtering separates an undissolved solid from a liquid: the crystals stay on the filter paper, and the liquid passes through. The glass now holds 45 g of salt at 20 °C: some dissolved, some in a pile. Evaporating the liquid that passed through gives back the solute.

Step 5 of 6

Crystallisation

Another way to get a solid out of a solution is crystallisation: dissolve it in hot water, then cool it. As the solubility falls, the excess comes out of solution as pure crystals. The glass holds 39 g of salt that all dissolved in boiling water, and now the solution has been cooled to 20 °C.

Step 6 of 6

Distillation

To keep the solvent instead, use distillation: boil the solution, lead the steam through a cooled tube, and collect the liquid that condenses in another vessel. The solute, whose boiling point is much higher, stays behind. In the Scene the water is at 373 K.