A fashion designer is developing a new range of clothing and wants to use natural dyes instead of synthetic dyes. Explain why synthetic dyes are generally preferred over natural dyes in the textile industry, and describe one way in which chromatography can be used to check the purity of a synthetic dye sample.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Natural dyes, such as those extracted from plants, have been used for thousands of years. However, the modern textile industry largely relies on synthetic dyes produced by chemists.
Model answer (5 marks)
Synthetic dyes give a wider range of colours than natural dyes.
Synthetic dyes are more colour‑fast and do not fade as quickly as natural dyes.
Synthetic dyes can be produced in large quantities and are cheaper to produce at scale.
Chromatography separates the components in the dye sample based on how far each component travels up the chromatography paper.
A pure dye produces only one spot on the chromatogram, whereas an impure sample produces more than one spot.
Synthetic dyes are more colour‑fast and do not fade as quickly as natural dyes.
Synthetic dyes can be produced in large quantities and are cheaper to produce at scale.
Chromatography separates the components in the dye sample based on how far each component travels up the chromatography paper.
A pure dye produces only one spot on the chromatogram, whereas an impure sample produces more than one spot.
Examiner tips
- Use the exact phrases from the mark scheme; each point counts as one mark.
- Show the chromatography principle and link it to purity in one sentence.
- Keep the answer concise – no extra explanation beyond the required points.
- Use UK spelling (e.g., colour).
Common mistakes
- Confusing colour‑fast with colour stability; both are acceptable but colour‑fast is the term used.
- Using ‘purity test’ instead of describing the chromatogram spots.
- Adding irrelevant details such as the type of solvent or the size of the paper.
Mark scheme (5 marks)
- Synthetic dyes produce a wider range of colours than natural dyes
- Synthetic dyes are more colour-fast / do not fade as quickly as natural dyes
- Synthetic dyes can be produced in large quantities / are cheaper to produce at scale compared to natural dyes
- Chromatography separates the components in the dye sample based on how far each component travels up the chromatography paper
- A pure dye produces only one spot on the chromatogram, whereas an impure sample produces more than one spot
Key terms in this question
synthetic dyes · natural dyes · chromatography
Related
- All OCR A-Level Chemistry B: Salters (H433) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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