Separation techniques

• Iron


  • Grey magnetic bits
• Sulfur


  • Bright yellow bits
• Iron and sulfur are shown together but not reacted
• Paper chromatography

  A method of separating substances in a mixture
• How to do paper chromatography

  1. Draw a line near the bottom of a sheet of filter paper

  2. Add a spot of the ink to the line and place the sheet in a beaker of solvent

  3. The solvent seeps up the paper, carrying the ink with it

  4. Each different dye in the ink will move up the paper at a different rate so the dyes will separate out

  5. When the solvent has nearly reached the top of the paper, take the paper out and leave it to dry

  6. The end result is a pattern of spots called a chromatogram
• Chemistry and fun are a mixture easily separated
• Solvent front


  The point the solvent has reached as it moves up the paper
• Filtration

  A method of separating insoluble solids from liquids
• Evaporation


  A method of separating a soluble salt from a solution by slowly heating the solution until the solvent evaporates and crystals form
• Crystallisation


  A method of separating a soluble salt from a solution by allowing the solution to cool and the salt to form crystals
• How to separate rock salt (salt and sand)

  1. Grind the mixture to make the salt crystals small

  2. Put the mixture in water and stir, the salt will dissolve but the sand won't

  3. Filter the mixture, the sand will be left on the filter paper while the salt solution passes through

  4. Evaporate the water from the salt solution to leave dry salt crystals
• Simple distillation


  A method of separating a liquid from a solution by heating the solution and collecting the vapour that condenses
• Fractional distillation

  A method of separating a mixture of liquids with similar boiling points by using a fractionating column
• How fractional distillation works

  1. Put the mixture in a flask and heat it

  2. The liquid with the lowest boiling point evaporates first and reaches the top of the fractionating column

  3. Liquids with higher boiling points may also start to evaporate but will only get part way up the column before condensing and running back down

  4. Collect the fractions as the temperature is raised to separate the different liquids
• simple distillation

  1. A solution is heated, usually using a Bunsen burner.
  2. The liquid in the mixture evaporates into a gas. 
  3. The gas is cooled by a water jacket, and condenses into a liquid, which then flows into the beaker.