A pharmacist says that a medicine they have made is a formulation. Describe what is meant by a formulation and explain why medicines are classed as formulations rather than pure substances.

AQA GCSE Chemistry (8462) — 4.8.1 Purity, formulations and chromatography · Describe · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

A formulation is a mixture that has been designed as a useful product.
The components are mixed in carefully measured quantities to ensure the product has the required properties.
A pure substance contains only a single element or compound, not mixed with any other substance.
A medicine contains more than one component / is a mixture, so it cannot be a pure substance.

Examiner tips

  • Use the definition of formulation first, then contrast with pure substance.
  • Mention that medicines are mixtures of active ingredient(s) and excipients.
  • Show the reason for measuring components – to give the required properties.

Common mistakes

  • Confusing formulation with a single drug; not recognising excipients.
  • Lacking the point that medicines are mixtures, not pure substances.
  • Using vague language such as ‘made of many parts’ instead of ‘mixture of components’.

Mark scheme (4 marks)

  1. A formulation is a mixture that has been designed as a useful product
  2. The components are mixed in carefully measured quantities to ensure the product has the required properties
  3. A pure substance contains only a single element or compound, not mixed with any other substance
  4. A medicine contains more than one component / is a mixture, so it cannot be a pure substance

Key terms in this question

formulation · pure substance

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