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CAIE IGCSE Chemistry 12.4 Separation and Purification Questions

Practise choosing filtration, crystallisation or distillation from mixture properties and using melting or boiling behaviour to assess purity.

Syllabus
2026–2028
Course
Chemistry 0620

Exam points

  • choose filtration for an insoluble solid and crystallisation to recover a dissolved solid
  • choose simple or fractional distillation by considering solvent recovery and boiling points
  • assess purity from a sharp melting or boiling point compared with the accepted value

Covered syllabus points

12.4.1—Methods of separation and purification12.4.2—Suggest suitable separation and12.4.3—Substances and assess their purity

Question 1

[Maximum number: 1]

Fermentation of sugar produces a mixture of ethanol solution and solid yeast.
How is the solid yeast removed from the mixture?

A

crystallisation

B

distillation

C

filtration

D

fractional distillation

Question 2

[Maximum number: 1]

A mixture contains salt, sand and sulfur.
Salt dissolves in water but not in xylene.
Sulfur dissolves in xylene but not in water.
Sand does not dissolve in water or xylene.
What is the order of the processes used to separate the salt, the sand and the sulfur from the mixture?

A

add water → filter → add xylene to the filtrate → filter

B

add water → filter → add xylene to the residue → filter

C

add xylene → filter → add water to the filtrate → filter

D

add xylene → filter → add xylene to the residue → filter

Question 3

[Maximum number: 1]

Which substance should be pure for the intended use?

A

a drug for curing disease

B

limestone for iron extraction

C

petroleum for fractional distillation

D

water for washing a car

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