Separating Techniques

Separating Techniques

1. Solutions

   • Solute: the solid or gas in a solution
   • Solvent: the liquid in a solution
   • Solution: when a solvent and a solute dissolve to form one
   • Not all solvents are the same. For example, water cannot dissolve nail varnish but propanone can, and they are both solvents
   • When the solvent has taken up as much solute as it can, the solute begins to consume the solvent. This is a saturated solution

2. Filtration

   • Inside filter paper, there are very tiny holes called pores where liquids can flow through them but not solids
   • Filtrate: what has passed through the filter paper
   • Residue: what hasn't passed through the filter paper
   • I like to think of filter paper as a mini colander of sorts - most solids can't pass through but sometimes, little pieces are able to squeeze past

3. Distillation

   • 1. A solution is heated up enough for the liquid to evaporate and rise as water vapour
   • 2. The water vapour travels through a condensing column where it cools down back into a liquid
   • 3. The distilled liquid falls into the round bottom flask
   • Distillation uses evaporation and condensation in order to separate a solution

4. Chromatography

   • Chromatography is a method of separating solutions according to their colour
   • Mixtures that are suitable for chromatography can include ink, food colouring and dyes
   • Chromatography is carried out on special paper, where a dab of the mixture is placed almost but not quite at the bottom of a piece of chromatography paper and the paper is placed upright in a solvent such as water.
   • As the solvent soaks up the paper, it carries the mixtures with it. Because different components of the mixture move at different rates, the mixture gets separated out

5. Evaporation

   • This technique uses a heating device (usually something like a bunsen burner) to heat up a solution to just the amount that is needed to boil the part with the lowest boiling point
   • Example: say you wanted to remove ethanol from water, water has a boiling point of 100 degrees celsius, whereas ethanol has a boiling point of somewhere around 75 degrees if memory serves. You would heat the solution up to just over 75 degrees so that the ethanol boiled away but the water stayed as a normal liquid