Filtration and Crystallisation

• Physical separation techniques can only be used to separate mixtures, they cannot be used to separate the elements in a compound
• Chemical reactions such as reduction or electrolysis can be used to separate the elements in compounds
• Filtration


  Used to separate an insoluble solid from a liquid
• Insoluble


  The solid will not dissolve in the liquid
• Insoluble solid


  • Silver chloride
• Solvent


  • Water
• Filtration process


  1. Pour mixture into filter paper

  2. Liquid (filtrate) passes through

  3. Solid trapped in filter paper
• Crystallization


  Used to separate a soluble solid from a liquid
• Soluble solid


  • Sodium chloride
• Crystallization process


  1. Sodium chloride dissolves in water to form solution

  2. Water evaporates leaving behind solid sodium chloride crystals
• Heating can be used to speed up evaporation in crystallization, but care is needed as some chemicals may break down when heated