C1 - Seperation Techniques

• Name the four physical processes that can be used to separate mixtures

  • Filtration
  • Crystallisation
  • Distillation / Fractional Distillation
  • Chromatography
• Describe the Process of Filtration

  Filtration is used to separate an insoluble solid is suspended in a liquid.

  The insoluble solid (called a residue) gets caught in the filter paper,

  because the particles are too big to fit through the holes in the paper.

  The filtrate is the substance that

  comes through the filter paper.

  Apparatus: filter paper + funnel.

  
• Describe the process of Crystallisation

  Crystallisation only remove somes of the solvent by evaporation to form a saturated solution (the one where no more solid can be dissolved).

  Then, we cool down the solution. As we do it, the solid starts to crystallise, as it becomes less soluble at lower temperatures.

  The crystals can be collected and separated from the solvent via filtration.

  
• Describe the process of Distillation.

  Simple distillation is used to separate liquid from a solution – the liquid

  boils off and condenses in the condenser. The thermometer will read the boiling point of the pure liquid.

  Contrary to evaporation, we get to keep the liquid.

  
• Describe the process if Fractional Distillation

  Fractional distillation is a technique for separation of a mixture of liquids.

  It works when liquids have different boiling points.

  The apparatus is similar to the one of simple distillation apparatus, with the

  additional fractionating column placed on top of the heated flask.

  The fractionating column contains glass beads. It helps to separate the compounds.

  In industry, mixtures are repeatedly condensed and vapourised.

  The column is hot at the bottom and cold at the top. The liquids will condense at different heights of the

  column.

  
• Describe the process of Chromatography.

  Chromatography is used to separate a mixture of substances dissolved in a solvent.

  In paper chromatography, we place a piece of paper with a spot containing a mixture

  in a beaker with some solvent. The bottom of the paper has to be in contact with the solvent. The solvent level will slowly start to rise, thus separating the spot (mixture) into few spots (components).

  
• How do you calculate the Rf Value?

  Distance of Dye ÷ Distance of Solvent
• Solute

  A substance that is dissolved in a solvent
• Solvent

  A substance that dissolves a solute to form a solution
• Solution

  A mixture formed when a solute is dissolved in a solvent
• Miscible


  Substances (particularly liquids) that mix together, e.g. water and alcohol
• Immiscible

  Substances (particularly liquids) that do not mix together, e.g. water and oil
• Soluble

  A substance that can be dissolved in a solvent, e.g. salt in water
• Insoluble

  A substance that won't dissolve in a particular solvent