separating techniques

• Simple distillation


  1. Heat solution

  2. Solvent vapour evaporates

  3. Gas moves away and is cooled and condensed

  4. Remaining solution becomes more concentrated in solute
• Simple distillation


  Used to separate a solvent from a solution. Useful for producing water from salt solution.
• Simple distillation


  • Dissolved solute has a much higher boiling point than the solvent
• Fractional distillation


  1. Heat mixture of liquids

  2. Liquids with different boiling points evaporate at different temperatures

  3. Vapour is cooled and condensed to form pure liquid
• Fractional distillation


  Used to separate a pure liquid from a mixture of liquids
• Fractional distillation


  • Separating ethanol from water
• Fractional distillation of crude oil

  1. Heat crude oil in fractionating column

  2. Oil evaporates and condenses at different temperatures

  3. Separate into fractions with similar number of carbon atoms
• Fractionating column


  Works continuously, heated crude oil is piped in at the bottom, vaporised oil rises up and fractions are tapped off where they condense
• Fractions from crude oil

  Can be processed to produce fuels and feedstock for petrochemical industry
• Filtration


  Filter solution to separate precipitate/insoluble salt from solution
• Filtration


  Used to separate a precipitate (insoluble salt) from a salt solution
• Crystallisation


  1. Warm solution to evaporate solvent

  2. Allow saturated solution to cool

  3. Solid crystals form and can be collected
• Crystallisation


  Used to separate a soluble salt from the solution it was dissolved in
• Paper chromatography


  1. Stationary phase and mobile phase

  2. Separation depends on distribution of substances between phases

  3. Calculate Rf value (distance moved by substance / distance moved by solvent)
• Paper chromatography


  Used to separate mixtures and identify substances
• Different compounds have different Rf values in different solvents, which can be used to help identify the compounds
• Compounds in a mixture may separate into different spots depending on the solvent but a pure compound will produce a single spot in all solvents
• Paper chromatography is an analytical technique that separates compounds by their relative speeds in a solvent as it spreads through paper
• The more soluble a substance is, the further up the paper it travels in paper chromatography
• Paper chromatography can be used to separate different pigments in a coloured substance