Separating Techniques

• We can normally separate mixtures into the elements or compounds that are found in them. We use physical processes to separate them. These processes don't create new chemical substances (there are no chemical reactions). Some separation processes are:
• Filtration

  • Separates mixtures of insoluble (can't dissolve) solids and liquids.
  • Done by pouring the mixture through filter paper:
  • The insoluble solid is trapped.
  • The liquid runs through the paper and is collected below.
• Crystallisation

  • Separates solutions into their constituent (different) parts: dissolved solids (solutes) and liquids (solvents).
  • Heat the mixture so that the solvent evaporates.
  • Eventually, crystals of the solute (dissolved solids) will form.
  • We can collect the solvent (liquid) by condensing it as it evaporates.

  
• Chromatography

  • Separates solutions with a number of different solutes (solids) in the solvent (liquid).
  • Place a drop of the solution to be separated near the bottom of a piece of chromatography paper. Dip the very bottom of the paper into a suitable solvent. The solvent (liquid) moves up the paper and carries the solutes (solids) in the solution with it.
  • Different solutes (solids) move at different speeds, so they separate on the paper.