C1 Atomic Structure: Separating Mixtures.

A mixture is mader up of two or more substances that aren't chemically bonded togethe. 

Filteration:

Used to separate substances which are insoluble in a particular solvent from those that are soluble in the solvent. For example, spearating (insoluble) sand from (soluble) water. The sand that you collect on the filter paper can then be washed with distilled water to remove the salt solution. The wet sand is then dried in an oven, which leaves the pure dry sand.

Crystallisation:

To obtain a sample of pure salt from the salt solution following filtration, you would need to separate the sodium chloride in the solution (called the filtrate) from the water. You can do this by evorating the water from from the soduim chloride. The best way to do this is by heating it in an evaporating dish on a water bath. Using a water bath is gentler way of heating than heating the evaporating dish directly on a tripod and gauze. The heating should be stopped when the solution is at point of crystalisation. This is when small crystals first appear around the edges. The rest of the saturated solution at room temperature should evaporate to leave crystals 

When you need to collect the solvent itself, distillation is the way to go.

In simple distillation, a solution is heated and boiled to evaporate the solvent. The vapour given off then enters a condenser, an outer glass tube with water flowing inside it from the glass tube to the flask, which cools the hot vapour and condensed back into a liquid. Any dissolved solids will remain in the heated flask.

In fractional distillation, the liquids mainly used have similar boiling points. To aid the process of simple distilliation a fractioning tube is used. 

A frationing tube is a long glass tube filled with beads, fitted virtically on top of the flask.

The vapours must pass over every bead, the temperature getting lower as the vapour goes up.

For example, frational distillation is used to separate ethanol (78 Degrees) and water (100 Degrees) 

Paper chromatography is used to separate and identify substances from mixtures in solutions. It works because some compunds will dissolve better than others in a solvent chosen.

A capillary tube is used to dab a spot of solution on a pencil line near the bottom of a sheet of absorbant chromatography paper. 

The more soluable a substance is in a solvent, the higher up it will be taken on the paper.

Different solvents can be used to maximise separation.