Chemistry Ch3 (26/11/2009)

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  • 1. Crystallization 1.Evaporate slowly at room temperature 2.Solution becomes more and more concentrated 3.Solution becomes saturated 4.Solid crystals slowly grow in size After the removal of insoluble impurities, pure crystals of common salt can be separated out by crystallization.
  • 2. water slowly evaporates at room temperature Experiment 3.1 sodium chloride crystals sea water more concentrated solution solution saturated with respect to sodium chloride sodium chloride crystals Experiment 3.1 Example
  • 3. Difference between Crystallization & Evaporation
    • Discuss in groups
    • compare the difference between them
    • purity
    • time consuming
    • products
    • temperature
  • 4. Difference between Crystallization & Evaporation
    • evaporation : heating to obtain powder, impure, quickly
    • crystallization : place it at room temperature to become saturated solution and from crystal, much more pure, slowly
  • 5. sea water water turns into vapour liquid in the cold receiver test tube boiling condensing Isolation of pure water from sea water By distillation , Learning tip
  • 6. Distillation using simple apparatus. end of delivery tube should be above the distillate delivery tube receiver test tube pure water (distillate) heat boiling tube clamp thermometer water (cooling agent) sea water anti-bumping granule (to prevent ‘bumping’ of solution) Distillation at home
  • 7. The distillation can also be carried out using ‘Quickfit’ apparatus. The solid left behind is called the residue . The pure liquid that distils over is called the distillate .
  • 8. A set of ‘Quickfit’ apparatus.
  • 9. Distillation using ‘ Quickfit’ apparatus. STSE connections 3.2 heat thermometer pear-shaped flask anti-bumping granule solution Liebig condenser receiver adaptor test tube (as receiver) cold water in (from tap) water out (to sink) thermometer bulb distillate cold water Experiment 3.2 Experiment 3 .2
  • 10. Chemical Analysis Chemical analysis Chemical identity Chemical composition