Separation & purification: IGCSE Chemistry questions with answers
Free Separation & purification questions for IGCSE Chemistry (0620), part of Experimental techniques & analysis. Each question has the answer and the marking points an examiner would look for.
A mixture contains salt, sand and iodine. Iodine sublimes on gentle heating; salt dissolves in water; sand does not. Which order of steps gives all three substances separately?
A heat gently to sublime the iodine; add water to the residue and filter; evaporate the filtrate
B filter the dry mixture; heat gently; add water
C add water and evaporate; heat gently; filter
D add water and filter; heat the residue gently; evaporate the filtrate
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Answer: A
Question 2Multiple choice · 1 mark
Which statement describes residue?
A The solid left on the filter paper
B A mixture of a metal with other elements, such as brass (copper and zinc)
C The liquid that passes through the filter paper
D The separation of miscible liquids with different boiling points
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Answer: A
Question 3Multiple choice · 1 markA* challenge
A mixture contains salt, sand and iodine. Iodine sublimes on gentle heating; salt dissolves in water; sand does not. Which order of steps gives all three substances separately?
A filter the dry mixture; heat gently; add water
B add water and evaporate; heat gently; filter
C add water and filter; heat the residue gently; evaporate the filtrate
D heat gently to sublime the iodine; add water to the residue and filter; evaporate the filtrate
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Answer: D
Question 4Structured · 4 marksA* challenge
Crude oil is separated by fractional distillation.
(a)
Explain how fractional distillation separates the fractions.
[3]
(b)
Describe how the viscosity of the fractions changes with chain length.
[1]
Show answers and mark scheme
Part
Answer and marking points
Marks
(a)
different boiling points; condense at different heights
crude oil is heated and vaporised B1 the fractionating column is hotter at the bottom and cooler at the top B1 fractions condense at different heights according to their boiling points B1
3
(b)
increases
viscosity increases as the chain length increases B1
1
Question 5Structured · 5 marks
Rock salt is a mixture of sand and sodium chloride.
(a)
Describe how to obtain pure, dry salt crystals from rock salt.
[4]
(b)
Name the method used to separate ethanol from water.
[1]
Show answers and mark scheme
Part
Answer and marking points
Marks
(a)
dissolve, filter, evaporate, crystallise
add water and stir to dissolve the salt B1 filter to remove sand B1 heat the filtrate to evaporate some water B1 leave to crystallise and dry the crystals B1
4
(b)
fractional distillation
fractional distillation B1
1
Question 6Structured · 4 marks
A mixture of two miscible liquids with different boiling points is separated.
(a)
Name the method.
[1]
(b)
Explain the role of the fractionating column.
[2]
(c)
State how the purity of the collected liquid can be checked.
[1]
Show answers and mark scheme
Part
Answer and marking points
Marks
(a)
fractional distillation
fractional distillation B1
1
(b)
temperature gradient; repeated condensation
it has a temperature gradient B1 vapours condense and re-evaporate, so the liquid with the lower boiling point reaches the top B1
2
(c)
boiling point
measure its boiling point (a pure liquid boils at a fixed temperature) B1
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Original Cambridge-style practice questions written for mentorriyaz.in. These are not Cambridge past paper questions, and this site is not affiliated with or endorsed by Cambridge University Press & Assessment. Updated 2026-11-04. Paper generator · mentorriyaz.in