Elements, Compounds and Mixtures

• Periodic table

  • Around 100 different elements
• Element

  All the atoms are the same
• Compound

  Two or more different elements chemically combined
• Mixtures

  Two or more different elements not chemically combined
• Physical separation techniques

  • Filtration
  • Distillation
  • Crystallisation
  • Chromatography

  Can only be used to separate mixtures
• Molecule

  Any elements that are chemically combined
• Filtration

  • Used to separate an insoluble solid from a liquid

  1. Pour mixture into filter paper
  2. Liquid then passes through the pores in the filter paper (known as filtrate)
  3. Solid material is collected at the filter paper as it cannot pass through
• Crystallisation

  • Used to separate a soluble solid from a liquid

  1. Leave solution out which will cause it to evaporate
  2. This will leave behind solid crystals

  • Process can be sped up by gently heating the solution to evaporate it
• Simple distillation

  
  

  Used to separate a liquid from a solid, if you want to keep the liquid

  1. Evaporate liquid by heating it to turn it into vapour
  2. Vapour condenses back to liquid by cooling
• Fractional distillation


  Used to separate mixtures with different boiling points

  1. Gently heat mixture
  2. Liquids will then start to evaporate
  3. But liquid with the lower boiling point will evaporate more easily
  4. Two different vapours then travel to the fractionating column
  5. In the column, they condense and drip back into the flask where they evaporate again
  6. Vapours then pass into the condenser and turn back into a liquid