Filtration + Crystallisation

• What is evaporation used for ?

  Separate a dissolved solid from a liquid.
• What is a pure substance ?

  A substance that is made up of only one type of element or atom.
• How would you isolate the sand and salt from a mixture of salt and sand ?

  Filtration + Evaporation

  1. Place the mixture in water and stir. Salt will dissolve but sand won’t
  2. Pour the mixture through filter paper and funnel . Sand will get stuck on the filter paper.
  3. Evaporate the water by heating . This will leave behind the salt.
• Why would the salt dissolve but the sand won’t .

  Salt is a soluble solid while sand is an insoluble solid.
• Describe Technique for evaporation

  Evaporation

  • Place solution in an evaporating dish on a tripod
  • Heat solution with bunsen burner until all of the solvent evaporates and only solid remains
• What are the 6 methods through which mixtures can be separated ?

  • Filtration
  • Chromatography
  • Crystallisation
  • Evaporation
  • Simple Distillation
  • Fractional Distillation
• What is filtration used for ?

  Separate insoluble solids from liquids.
• Describe technique for crystallisation

  • Pour solution into an evaporating dish
  • Heat it using Bunsen burner ( needs to be heated more gently ).
  • Stop heating it when crystals start to form (‘point of crystallisation’) and allow to cool down.
  • Filter out crystals using filter paper and funnel .
  • Dry crystals by leaving it out to dry, warming oven or a desiccator.
• Drawback of evaporation that rather leads to use of crystallisation ?

  The excess heat used in evaporation can sometimes cause crystals to break down by thermal decomposition !
• Describe the technique for filtration

  Filtration

  • Place a piece of filter paper in a funnel ,and put funnel over a beaker.
  • Pour your mixture through the funnel.
  • Any insoluble solids will be caught by the filter paper ,we call this the residue
  • Any liquid or dissolved substances will pass straight through , we call this filtrate.
• Benefit of Evaporation

  Relatively quick and easy to separate solid from a solution
• What is a solution ?

  A mixture that contains a solute dissolved in a solvent.
• What do soluble and insoluble mean ?

  Soluble: able to be dissolved in a solvent. Insoluble: not able to be dissolved in a solvent.
• What is Chromatography used for ?

  Separates components of a mixture based on their solubility
• As the solution cools in crystallisation more crystals will start to form. Why is this ?

  Solids are less soluble at COLDER TEMPERATURES
• What do physical separation techniques only separate ?

  Mixtures