Notes

1. SEE PAST PAPER QUESTIONS BELOW
SUMMARY OF SEPARATION PROCESSES
COMPONENTS
OF THE
MIXTURE TO
BE SEPARATED
PROPERTY IN
WHICH
COMPONENTS
DIFFER
METHOD OF
SEPARATION
EXAMPLES
1. Two solids
one soluble
and one
insoluble
Solubility in
solvent
Dissolving→Filtration→
Evaporation
Add the mixture to the
solvent.
Filter off insoluble solid to
obtain the soluble solid by
evaporation of the solution.
Sodium chloride and sand.
2. Two miscible
liquids
Boiling point Simple Distillation or
fractional distillation
Alcohol and water
3. Two
immiscible
liquids
Density Floatation: Use a
separation funnel
i) Oil and water
ii) Benzene and water
iii) Mercury and water
4. Insoluble
solid and
liquid
Size of particles Filtration Clay and water
Limestone (CaCO3) and water
5. Solid or
liquids
Solubility in
solvent and
attraction to
absorbing medium
(Chromatography
e.g. filter paper)
Chromatography. Allow
solvent to flow over the
mixture on the filter paper
i) Dyes in ink or
indicators e.g. screened
(Methyl, Orange)
ii) Amino Acids from
Protein
iii) Hydrolysis products of
disaccharides(complex
sugars)
6. Two solids One can sublime
on heating
Sublimation. Heat the
mixture
i) Sodium Chloride and
ammonium chloride
ii) Iodine solid and sand.
Evaporation – This is used to obtain a soluble solid (solute) from its solution. It recovers the solute from the
solution by evaporating away the solvent, but not the solute. The liquid water evaporates to leave the solid behind
since the water has a much lower boiling point than the solid. Evaporation separates based on differencesin
boiling point. e.g. Copper (II) sulphate crysta1 from copper (II) sulphate solution. This method is also used to
prepare soluble salts.
Crystallisation: Another method of separating a dissolved solid from a solvent involves heating the solution to boil
off some of the solvent. This creates a saturated solution. A saturated solution is one in which no more solid can
dissolve at that temperature.The saturated solution is then cooled. The dissolved solid (solute) becomes less
soluble and so cannot remain dissolved. Consequently, it crystallises out of solution. The crystals may then be
separated from the saturated solution by filtration. Many salts, for example copper(II) sulfate, are separated from
their solution by crystallisation
FRACTIONAL DISTILLATION – This method is used to separate two or more liquids with different boiling
points e.g. The fractions from crude oil (petroleum); ii) Oxygen and nitrogen from liquid air

2. SIMPLE DISTILLATION – This method is used to separate a volatile substance from a non-volatile substance
e.g. i) pure water from sea water· ii) pure water from impure water. Or it can also be used to separate two liquids
with different boiling points e.g. Ethanol (b.p 81°C) and water b.p (100°C)
MAGNETIC SEPARATION – This method can be used to remove pieces of iron·(e.g. iron filings) from other
non-magnetic materials. For example: sulphur powder and iron filings.
Purifying a solid
Type of mixture Method When used
Solid/liquid
Solid/solid
Filtration
Crystallisation
Chromatography
Dissolving and filtration
To separate a solid from a 1iquid or
solution in which it is insoluble
To separate a solid from a liquid or
solution in which it is soluble
To separate solids from liquids when
only small amounts are available
To separate a solid which is soluble
from a solid which is insoluble
Purifying a liquid
liquid/solid
liquid/liquid
Distillation
Filtration or distillation
Fractional distillation
Layer separation (floatation)
To separate a liquid from a soluble
solid
To separate a liquid from an
insoluble solid
To separate two miscible liquids
(simple distillation gives poor
separation).
To separate two immiscible liquids
Purifying a gas
gas/gas Liquifaction
Chemical absorption
to separate gases when one is more
easily liquified than the other
to separate gases when one of them
can be removed chemically
It Is Important to understand what is achieved by filtration, washing, crystallization, distillation and distillation with
a fractionating column. Then from acknowledge of solubilities, miscibilities and boiling points you can work out the
best way to separate at mixture of chemicals.
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Source: AQA PAPER 2 H - SAMPLE SET 1 Q7 ANSWERS
1. A student investigated food dyes using paper chromatography.
This is the method used.
1. Put a spot of food colouring X on the start line.
2. Put spots of four separate dyes,A, B, C and D, on the start line.
3. Place the bottom of the paper in water and leave it for severalminutes.
Figure 5 shows the apparatus the student used.

3. 1.1) Write down two mistakes the student made in setting up the experiment and explain what problems one of the
mistakes would cause. [2 marks]
Another student set up the apparatus correctly.
Figure 6 shows the student’s results. The result for dye D is not shown.
Note:The solvent front is the distance travelled by the mobile phase (water) from the start line.

4. 1.2) Calculate the Rf value of dye A
Rf = distance moved by substance
distance moved by solvent
Give your answer to two significant figures. [3 marks]
Rf value = ________________________
1.3) Dye D has an Rf value of 0.80. Calculate the distance that dye D moved on the chromatography paper. [1 mark]
Distance moved by dye D = ________________________
1.4) Explain how the different dyes in X are separated by paper chromatography. [4 marks]
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2. Mixtures may be separated in the laboratory in many different ways. Three different methods of separating
mixtures are shown below.
METHOD 1 METHOD 2 METHOD 3
a) Name each method of separation. (3 marks)
(1)_______________________________________
(2) _______________________________________
(3) _______________________________________
b) Which method (1, 2 or 3) would be most suitable for obtaining water from potassium
chloride solution? (1 mark)
__________________________________________

5. c) Which method would be most suitable for removing sand from a mixture of sand and
water? (1 mark)
________________________________________________________________________
d) State why Method 1 would not be suitable to separate copper(II) sulfate from copper(II)
sulfate solution. (1 mark)
_________________________________________________________________________
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3.
Drinking water has been distilled from sea water since at least 200AD when the process
was described clearly by the Greek philosopher Aristotle. The distillation apparatus used to
separate pure water from salt solution in the laboratory is shown below.
3.
a) Name the solute in salt solution. (1 mark)_________________________________
b) Name the solvent in salt solution. (1 mark) _______________________________
c) What is solid A? Suggest its purpose. (2 marks) ________________________________________
_________________________________________________________________________________
d) What labels should be inserted at positions 6 and 7 ? (2 marks)
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e) Name the piece of apparatus labelled 5. (1 mark)
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f) What is the temperature on the thermometer when distillation is occurring? What does this suggest? (2 marks)
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g) What happens to the salt dissolved in the solution during this process? (1 mark)
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6. h) Distillation involves evaporation. What is meant by evaporation? Where in the apparatus does distillation take
place?
___________________________________________________________________________________
(2 marks)
i) Distillation involves condensation. What is meant by condensation? Where in the apparatus does condensation
take place? (2 marks)
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4. The table below contains a list of mixtures. In the right hand column, next to each mixture, write the best method
for separating the mixture into its components. [8 marks]
Method ofSeparation:Simple distillation, floatation, fractional distillation, sublimation, crystallization, dissolving
and filtration, chromatography, magnetic separation
Substance and Mixture Method ofseparation
1.Ethanol from ethanol and water
2. Salt from sea water
3. The different colours in black ink
4. Sand from a mixture sand and iron filings
5. Mercury from a mixture of water,cooking oil and
mercury
6. Water from muddy water
7. Crushed diamond from a mixture sodium chloride and
crushed diamond
8. Ammonium chloride from a mixture ammonium
chloride and sodium chloride
(b) Draw THREE labelled diagrams to show how you would carry out the separation for #5.