Filtration, evaporation and crystallization

• Separating soluble and insoluble solids from liquids

  1. Filtration

  2. Evaporation

  3. Crystallization
• Mixture


  Liquid and insoluble solid
• Solution


  Liquid and soluble solid (solute) dissolved in solvent
• Filtration


  Pour mixture through filter paper with small holes to separate insoluble solid from liquid
• Cannot filter out soluble solid from solution
• Evaporation


  Heat solution to evaporate solvent, leaving behind solid crystals
• Evaporation


  • Relatively quick and easy
  • Some solids may decompose when heated (thermal decomposition)
• Crystallization


  1. Heat solution gently to evaporate some solvent, then cool to allow crystals to form

  2. Filter out crystals

  3. Dry crystals
• Solids are less soluble at colder temperatures
• Crystallization is a slower technique than evaporation, used for solids susceptible to thermal decomposition