A food technologist is developing a new sports drink. The drink contains water, glucose, sodium chloride, flavourings and colourings. Explain why the sports drink is described as a formulation rather than a pure substance, and describe how paper chromatography could be used to find out whether one of the colourings in the drink is a pure substance or a mixture.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A food technologist is developing a new sports drink. The drink contains water, glucose, sodium chloride, flavourings and colourings.
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. The sports drink contains water, glucose, sodium chloride, flavourings and colourings – more than one substance – so it is a mixture, not a single element or compound, and therefore is described as a formulation.
To test whether one of the colourings is a pure substance or a mixture, place a small spot of the colouring on the baseline of a strip of chromatography paper. Immerse the paper in a suitable solvent (mobile phase). The solvent rises up the paper (stationary phase) carrying the components of the colouring. If the colouring is a pure substance, only one spot will appear on the paper. If it is a mixture, two or more spots will be observed.
To test whether one of the colourings is a pure substance or a mixture, place a small spot of the colouring on the baseline of a strip of chromatography paper. Immerse the paper in a suitable solvent (mobile phase). The solvent rises up the paper (stationary phase) carrying the components of the colouring. If the colouring is a pure substance, only one spot will appear on the paper. If it is a mixture, two or more spots will be observed.
Examiner tips
- Use the definition of a formulation – mixture of pure substances – to justify the first part. Show the step‑by‑step procedure for paper chromatography. Explain the outcome (single vs multiple spots) to answer the second part.
Common mistakes
- Confusing a formulation with a pure substance; forgetting to mention that the drink contains more than one substance. Not describing the chromatography steps (placing spot, solvent, stationary/mobile phases). Failing to state the expected result (single spot = pure, multiple spots = mixture).
Mark scheme (5 marks)
- A formulation is a mixture designed for a particular use / made up of exact quantities of pure substances
- The sports drink contains more than one substance / is not a single element or compound
- Place a spot of the colouring on the baseline of a piece of chromatography paper and place the paper in a suitable solvent
- The solvent (mobile phase) travels up the paper (stationary phase) carrying the substances in the colouring
- If the colouring produces a single spot it is a pure substance; if it produces more than one spot it is a mixture
Key terms in this question
formulation · pure substance · paper chromatography · mixture
Related
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