A sports drink manufacturer produces a new energy drink. The drink contains water, glucose, sodium chloride, citric acid and food colouring, each added in carefully measured quantities to give the drink its required properties. Explain why the energy drink is described as a formulation and not a pure substance, and describe one method that could be used to show that the drink contains more than one substance.

Eduqas A-Level Chemistry — 1.4 States of matter · Explain · 5 marks · View as Markdown

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

A sports drink manufacturer produces a new energy drink. The drink contains water, glucose, sodium chloride, citric acid and food colouring, each added in carefully measured quantities to give the drink its required properties.

Model answer (5 marks)

A formulation is a mixture that has been designed for a particular use and is made up of exact quantities of pure substances, whereas a pure substance is a single element or compound that has a fixed composition.

The energy drink contains water, glucose, sodium chloride, citric acid and food colouring – five different compounds – so it is a mixture, not a single pure substance.

A pure substance has a sharp, specific melting or boiling point. A mixture will melt or boil over a range of temperatures because the different components have different melting/boiling points. The energy drink would therefore not have a single melting or boiling point.

One way to demonstrate that the drink contains more than one substance is paper chromatography. When a small amount of the drink is applied to chromatography paper and developed in a suitable solvent, the different components will move different distances, producing several distinct spots. The presence of more than one spot shows that more than one substance is present.

Examiner tips

  • Use the definition of a formulation – mixture of pure substances – to justify the first part.
  • Mention the range of melting/boiling points to show it is not a pure substance.
  • State paper chromatography as the method and explain that multiple spots indicate multiple substances.

Common mistakes

  • Confusing a mixture with a solution and saying it is a pure substance.
  • Failing to mention the range of melting/boiling points.
  • Choosing a method that does not separate components, e.g. simple filtration, and not explaining how it shows more than one substance.

Mark scheme (5 marks)

  1. A formulation is a mixture designed for a particular use / made up of exact quantities of pure substances
  2. The drink contains more than one compound/element / it is not a single element or compound
  3. A pure substance has a sharp / specific melting point whereas a mixture melts over a range of temperatures — so the drink would melt/boil over a range
  4. Correct identification of a suitable method — paper chromatography (or simple/fractional distillation) — to show more than one substance is present
  5. Correct description of how the method shows more than one substance — e.g. for chromatography: the mixture separates into more than one spot on the paper / different substances travel different distances; OR for distillation: different liquids are collected at different temperatures / the mixture boils over a range

Key terms in this question

formulation · pure substance

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