crystalisation

• Recrystallisation


  1. Heat the solution to allow the solvent to evaporate and leave a saturated solution

  2. Dip a clean, dry, cold glass rod into the solution to test if it is saturated

  3. Crystals will form on the glass rod if the solution is saturated

  4. Allow the saturated solution to cool slowly

  5. Crystals begin to grow as solids come out of solution due to decreasing solubility

  6. Collect the crystals by filtering the solution, wash with cold distilled water to remove impurities, then allow to dry
• Recrystallisation


  Used to separate a dissolved solid from a solution, when the solid is much more soluble in hot solvent than in cold (e.g., copper sulphate from a solution of copper (II) sulphate in water)
• Crystallisation


  Longer process but big crystals made
• Crystallisation


  1. Separate soluble solid from solution

  2. Use Bunsen burner on low, blue flame

  3. Pour solution in evaporating dish and gently heat

  4. Solution some solvent will evaporate and leave a concentrated/saturated solution

  5. Remove dish from the heat and leave solution to cool

  6. Dip clean dry, cold glass rod into the solution

  7. Crystals will form on glass rod if it is saturated

  8. Solid crystals come out due to decreasing solubility in cold highly concentrated solution

  9. Filter crystals from solution, wash with cold, distilled water to remove impurities

  10. Leave to dry in drying oven or desiccator
• Crystalisation can be used for solids that thermally decompose (break down) when heated eg. salt crystals
• Next to chemical/word symbols of a reaction there is either a (S) for solid or (aq) for aqueous. aqueous solutions means its dissolved in a solution and will require a process like evaporation or crystallisation. solid can be done with filtration