Mixtures and Separation Techniques 2

Mixtures and Separation Techniques 2

1. All substances can be described as pure or impure

   • impure
     • ALL impure substances are mixtures
   • pure
     • water is a good example of a pure substance

2. mixtures

   • definition: two or more substances NOT chemically bonded together
   • example of mixtures include: solutions, where a solute is dissolved in a solvent
   • other examples include blood, crude oil and air
   • A mixture of an insoluble liquid is called a suspension. The insoluble solid can be removed by FILTRATION. The solid left in the filter paper is the RESIDUE and the liquid passing through is called the FILTRATE.
   • A mixture of dyes can be separated by CHROMATOGRAPHY. This uses the fact that the dyes have different solubilities in the solvent

3. water

   • water is a common solvent
   • The test for water uses ANHYDROUS COPPER SULPHATE, which turns from white to blue in the presence of water
   • ONLY pure water will boil at 100 C and this can be used to test the purity of water
   • Evapouration of some of the warer from a solution can lead to a SATURATED SOLUTION (one in which no more solute can dissolve), which can then be left to CRYSTALISE by the slow evaporation of the remaining water.

4. Distillation

   • SIMPLE DISTILLATION can be used to seperate MISCIBLE LIQUIDS with DIFFERENT boiling points and that the pure liquid collected is called the DISTILLATE.
   • simple distillation can also be used to separate a solute from the solvent in a solution;
   • FRACTIONAL DISTILLATION can be used to seperate mixtures of many miscible liquids with SIMILAR boilling points. This process is used in in the processing of crude oil to separate out the many FRACTIONS, e.g. the petrol fraction.