Separating mixtures

• Mixture


  Two or more elements or compounds, which are not chemically combined
• Mixture


  • Components retain their own properties
• Physical processes


  Used to separate mixtures, do not involve chemical reactions, no new substances are made
• Filtration


  1. Used to separate soluble solids from insoluble solids

  2. Dissolve soluble solid (e.g. salt) in water

  3. Filter the mixture
• Crystallisation


  1. Used to obtain a soluble solid from a solution

  2. Gently warm the mixture

  3. Water evaporates leaving pure solid crystals
• Simple distillation


  1. Used to obtain a solvent from a solution

  2. Heat the solution to 100°C

  3. Water changes from liquid to gas

  4. Water condenses and collects as pure liquid
• Required practical: Analysis and purification of water samples from different sources
• Water sample analysis and purification

  1. Use pH probe or indicator to analyse pH

  2. Heat sample to 100°C to evaporate water

  3. Collect pure water in condenser

  4. Measure mass of solid residue to find dissolved solids
• Hazards and risks: Experimenter may burn themselves on hot equipment
• Fractional distillation


  1. Used to separate mixtures with components of different boiling points

  2. Oxygen and nitrogen can be obtained from liquid air
• Chromatography


  1. Used to separate soluble, coloured components of a mixture

  2. Different colours in fizzy drink can be separated