Filtration & Crystalisation

• A small amount of sodium chloride is dissolved into a beaker of water. Which of the following is the solvent?

  Water

  A solvent is a liquid in which substances can dissolve.
• Soluble definition


  Solid substances that can dissolve in liquids are described as soluble.
• Insoluble definition 


  Solids that cannot dissolve are described as insoluble
• True or False? Filtration involves using a Bunsen burner flame to evaporate a solvent from a solution.

  False

  No, that process is called 'evaporation' not 'filtration'. 
• What is filter paper?

  Filter paper is full of small holes that are large enough to allow liquid particles to move through, but too small to allow solids through. This separates the solids from the liquids in filtration.
• What is the best method to obtain a sample of salt from a salt solution?

  Evapouration

  Filtration can only separate undissolved solids from a liquid, and fractional distillation is used to separate multiple liquids
• Describe how you would carry out the process of crystallisation.

  First, pour the solution into an evaporating dish and heat it using a Bunsen burner. 

  Stop heating it when crystals start to form ('point of crystallisation') and allow it to cool down.

  Then either leave it to allow the rest of the water to evaporate, or filter out the crystals using filter paper and a funnel. Lastly, dry the crystals in a warm oven.
• Describe how you would carry out the process of crystallisation.

  Heat the solution until you start to see crystals forming

  Allow it to cool so that more crystals form

  Allow the rest of the water to evaporate // Filter out the crystals using filter paper and a funnel

  Dry the crystals e.g. by using a drying oven
• How would you separate pieces of rock from a solution of salt water?

  Filtration

  The rocks are solid and so can be captured by the filter paper, whereas the solution of salt water will pass straight through.
• A small amount of sodium chloride is dissolved into a beaker of water. Which of the following is the solvent?

  Water
• What is a 'pure' substance?

  A pure substance is one that only contains one type of element or compound.
• What are the 6 methods through which mixtures can be separated?

  1. Filtration
  2. Chromatography
  3. Crystallisation
  4. Evaporation
  5. Simple distillation
  6. Fractional distillation
• Describe the technique for evaporation.

  • Heat your solution until all of the solvent evaporates, and only solids remain.
  • (this is normally done by placing the solution in an evaporating dish on a tripod, and heating it with a bunsen burner)
• What is filtration used for?

  Filtration is used to separate insoluble solids from liquids.
• Describe the technique for crystallisation

  1. Pour the solution into an evaporating dish.
  2. Heat it using a Bunsen burner.
  3. Stop heating it when crystals start to form ('point of crystallisation') and allow it to cool down.
  4. Either leave it to allow the rest of the water to evaporate, or filter out the crystals using filter paper and a funnel.
  5. Dry the crystals in a warming oven or desiccator.
• What is a solution? 

  A solution is a mixture that contains a solute (the solid) dissolved in a solvent (the liquid)
• What is evaporation used for?

  Evaporation is used to separate a dissolved solidfrom a liquid.
• What is the benefit of using crystallisation rather than evaporation as a separating technique?

  The excess heat used in evaporation can sometime cause the crystals to break down by thermal decomposition.
• What is chromatography used for?

  Chromatography separates the components of a mixture based on their solubility.
• How would you isolate the sand and salt from a mixture of salt and sand?

  1. Place the mixture in water and stir. The salt will dissolve but the sand won’t.
  2. Pour the mixture through filter paper and funnel. The sand will get stuck on the filter paper.
  3. Evaporate the water by heating. This will leave behind the salt.
• Describe the technique for filtration.

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