A pharmacist is checking whether a batch of a medicine is a formulation or a pure substance. She is told that the medicine contains a painkiller, a binding agent and a coating material, each added in carefully measured quantities. Explain what is meant by the term 'formulation' and describe one difference in behaviour that would be observed if the melting point of this medicine were compared with that of the pure painkiller alone.

WJEC GCSE Chemistry (Wales) — 1.1 The nature of substances and chemical reactions · Explain · 4 marks · View as Markdown

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

A pharmacist is checking a batch of medicine before it is approved for sale. The medicine is made up of several components, each included in exact quantities to ensure the product has the required properties.

Model answer (4 marks)

A formulation is a mixture that has been designed for a particular use and is made up of exact, carefully measured quantities of pure substances.

The pure painkiller would have a sharp, specific melting point. The medicine, being a formulation, would melt over a range of temperatures rather than at a single point.

Examiner tips

  • Use the definition of formulation exactly as given in the mark scheme.
  • Mention that the medicine is a mixture of several pure substances.
  • Explain that a pure substance has a single melting point, whereas a mixture shows a melting range.
  • Keep the answer concise and to the point.

Common mistakes

  • Confusing a formulation with a single pure substance.
  • Failing to state that the medicine melts over a range of temperatures.
  • Using vague terms like "different" instead of "range of temperatures."

Mark scheme (4 marks)

  1. A formulation is a mixture designed for a particular use
  2. A formulation is made up of exact/carefully measured quantities of pure substances
  3. The pure painkiller would have a sharp/specific melting point
  4. The medicine (formulation/mixture) would melt over a range of temperatures

Key terms in this question

formulation · pure substance · melting point

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