Mixtures and Compounds

• A physical property of a substance is one which you can measure without changing the substance. Two examples of physical properties are melting point and appearance
• A chemical property of a substance which you can only observe by changing the substance
• A mixture is formed whenever elements or compounds are together but not joined chemically
• Mixtures have different physical properties to the substances that make them up. When they are separate, the substances in a mixture still keep their chemical properties
• The elements in a compound are joined chemically and therefore cannot be separated by physical means.
• Separating an insoluble solid from a liquid


  Filtration because the insoluble solid cannot pass through the filter paper
• Separating the liquid from a solution of a solid in a liquid. The liquid is the distillate

  Simple distillation because the liquid has a much lower boiling point and so evaporates at a much lower temperature
• Separating two or more miscible liquids

  Fractional distillation because the liquid with the higher boiling point condenses on the column, the liquid with the lower boiling point carries on up as a vapour
• Separating coloured substances

  Paper chromatography which relies on the substances having different attractions for the paper and the solvent
• Separating the dissolved solid from a solution

  Crystallisation which depends on the big differences in boiling points between the solvent and the dissolved solid