Separating%20Mixtures

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Separating Mixtures

• Chapter 25

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Decanting
Decanting means to pour off. Decanting is used in
panning gold and in pouring water off vegetables.
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Separating Solids from Liquids

• Filtration is the separation of small insoluble
  solids from a liquid. e.g. sand from water,Chalk
  from water

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Evaporation
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To purify Rock Salt(sand and salt) using
filtration and evaporation.
Step (a) Crush rock salt with pestle and
mortar. Step (b) Add crushed rock to warm
water. Step (c) Heat water and stir thoroughly.
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Step (d) Allow beaker to cool and filter the
mixture. Step (e) Heat the salt solution until it
starts to spit. Step (f) Continue heating the
solution over a beaker of boiling water until dry
salt remains in the dish.
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Distillation

• Distillation is the process involving the
  vaporisation of a liquid by boiling it and then
  condensing the liquid by cooling it.
• It can be used to separate a soluble solid (e.g.
  Salt) from a liquid (e.g.seawater) to give a pure
  sample of each.

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Apparatus used to obtain a sample of pure water
from seawater(distillation)
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Distillation can also be used to separate two
miscible liquids such as alcohol and water.

• It works on the basis that alcohol boils at 78o C
  and water boils at 100o C.
• The fractionating column helps to give better
  separation of the Alcohol and the Water

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Chromotography

• Chromatography is a method used to separate a
  mixture of dissolved substances in a solution.

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As the solvent rises up the paper it carries some
dyes further up than others. This separates the
various dyes from the original sample.
Before
After
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TextbookChapter24-Separating Mixtures
A1.Physical. A2. Insoluble. A3. Soluble,
solution. A4. Filtration, filter paper. A5.
Salt, sugar, evaporation, crystals, clock
glass. A6. 78, 100, distillation, Liebig
condenser. A7. Distillate. A8. Soluble,
solution. A9. Distillation. A10.
Chromatography, chromatography paper. A11.
Soluble. B1. See Experiment 25.1, p.148. B2.
See Experiment 25.3, p.148.
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• DiscoveringScience-TextbookSolutions28
• B3.
• (a) Distillation.
• Alcohol has a lower boiling point and there fore
  evaporates
• quicker than water does. The alcohol
  vapour enters the inner tube of the Liebig
  condenser, the walls of which are kept cold by
  the water flowing in the outer sleeve of the
  condenser. This condenses the alcohol vapour
  into alcohol liquid.
• (c) So that the outer tube will fill completely
  with cold tap water.
• B4. SeeExperiment24.3,p.146.
• B5.
• (a) A magnet.
• (b) Saw dust would float and could be scooped
  off.
• (c) Filtration followed by evaporation.
• (d) Filtration.
• (e) Evaporation, or distillation to save a
  sample of water.
• (f) A magnet.

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• B6. (a)Sand (b)Ink. (c)Alcohol. (d)Copper
  sulfate.(e)Salt and water. (f)Sand and water.
  (g)Alcohol and water.
• B7. See Experiment 24.1, p.145.
• B8. (a)Distillation.
• (b)Alcohol and water.
• (c)Liebig condenser.
• (d)Filtration.
• B9.(a)See Experiment 24.4,p.147.
• (b)The mixture of coloured inks would
  separate out and end up at different levels on
  the chromatography paper. A single coloured ink
  would only leave one mark on the chromatography
  paper.
• B10.
• (a) Liebig condenser. (b)Y. (c)Pure water, salt.
• B11.(a)The ink spot moves upwards and the
  different colours in the ink get separated out at
  different levels on the chromatography paper.
  (b)The ink spot would move upwards and only one
  mark would be left higher up on the
  chromatography paper.