Separation Methods

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Separation Methods

• Ways to separate mixtures Chapter 3 Matter
  Its Properties

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Separating Mixtures

• Substances in a mixture are physically combined,
  so processes bases on differences in physical
  properties are used to separate the components
• Numerous techniques have been developed to
  separate mixtures. Among these are
• Decanting
• Using a separating funnel
• Filtration
• Evaporation
• Distillation
• Crystallization
• Chromatography

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Decantation

• Decantation is a very quick method for separating
  a mixture of a liquid and a heavier solid.
• If we want to separate a mixture of water and
  sand, First, we should allow the sand to settle
  on the bottom of the container. Then we poured
  off the water at the top.
• The advantage of this method is quick, but there
  is a disadvantage of this method which is rough.
  It cannot be used to separate a mixture of a
  liquid and a light sold, such as chalk in water.
  The particles of chalk are suspended in the
  water. They are so light that they do not sink
  down to the bottom for a long time

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Filtration

• Used to separate heterogeneous mixtures composed
  of solids and liquids (e.g. suspensions such as
  mud/starch in water)
• Uses a porous barrier (filter paper) to separate
  the insoluble solid from the liquid
• Liquid (filtrate) passes through leaving the
  solid (residue) in the filter paper

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Filtration
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Crystallization

• Separation technique that results in the
  formation of pure solid particles from a solution
  containing the dissolved substance
• As the solvent evaporates, the dissolved
  substance comes out of solution and collects as
  crystals
• Remember that it is the water (or solvent) that
  evaporates away, not the solution
• Produces highly pure solids
• Rocky candy is an example of this

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Evaporation
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Separating funnel

• Immiscible liquids, such as oil and water can be
  separated by using a separating funnel.
• The mixture is put into a separating funnel,
  shaken and allowed to settle.
• The oil and water from two separate layer. The
  liquid with higher density, in this case water
  forms the lower layer.
• Remove the stopper and open the tap after
  standing. The water runs out through the tap.
• The oil remains in the funnel and can be run out
  into another beaker

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Using a separating funnel
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Distillation

• This is good for separating a liquid from a
  solution. For example, water can be separated
  from salty water by simple distillation.
• This method works because the water evaporates
  from the solution, but is then cooled and
  condensed into a separate container. The salt
  does not evaporate and so it stays behind.

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Simple distillation
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Simple distillation (contd)
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Fractional Distillation

• This is good for separating two or more liquids
  from each other.
• For example, ethanol (alcohol) can be separated
  from a mixture of ethanol and water by fractional
  distillation.
• This method works because the two liquids have
  different boiling points.

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Fractional Distillation

• Water and ethanol solution is heated

• The ethanol reaches boiling point
  and starts to
  evaporate

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Fractional Distillation (contd)

• The ethanol has evaporated, and the water vapour
  has been cooled and condensed

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Chromatography

• A series of techniques used to separate a complex
  mixture of substances
• The mixture is dissolved in a fluid called the
  mobile phase, which carries it through a
  structure holding another material called the
  stationary phase. The various constituents of the
  mixture travel at different speeds, causing them
  to separate.

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Paper Chromatography

• There are many different types of chromatography
  methods one of which is PAPER CHROMATOGRAPHY
• This is good for separating, for example,
  dissolved substances that have different colours,
  such as inks and plant dyes.
• It works because some of the substances dissolve
  in the liquid better than others, so they travel
  further up the paper.
• Separation occurs because various components
  travel at different rates on the stationary phase
  (chromatography paper)
• Components with strongest attraction for paper
  travel the slowest

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Paper Chromatography
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Chromatography (contd)
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• The substances separated by chromatography do not
  have to be coloured. Colourless substance can be
  made to show up by spraying the paper with a
  locating agent. Then reacts with each of the
  colourless substances in order to produce a
  coloured product.
• We often used chromatography to identify the
  substances in a mixture. It is commonly used in
  hospital. It help doctors to find out whether the
  patient has diabetes, if paper chromatography
  might fund out whether sugar is present in the
  patient's urine.