State and explain why silver is used to make electrical contacts in high-quality switches, and why zinc is used to coat steel in the process known as galvanising. Give one reason for each use.

Cambridge International IGCSE Chemistry (0620) — 9.2 Uses of metals · State and explain · 4 marks · View as Markdown

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

Model answer (4 marks)

Silver is a good conductor of electricity and heat, so it allows electric current to pass through the contact with minimal energy loss.
Zinc is more reactive than iron, so it acts as a sacrificial metal; it corrodes preferentially, protecting the steel beneath from rusting even if the zinc layer is scratched.

Examiner tips

  • Use the exact terms "good conductor of electricity and heat" and "sacrificial metal".
  • Show the link between conductivity and minimal energy loss, and between reactivity and sacrificial protection.
  • Keep the answer concise – one sentence per use.

Common mistakes

  • Using vague phrases like "good material" instead of "good conductor".
  • Confusing zinc’s role as a protective coating with a galvanic cell explanation.
  • Writing the reasons in the wrong order or omitting the reactivity point.

Mark scheme (4 marks)

  1. Silver is a good conductor of electricity / heat
  2. This allows electric current to pass through the contact / circuit easily with minimal energy loss
  3. Zinc is more reactive than iron / steel (so acts as a sacrificial metal)
  4. Zinc corrodes / oxidises preferentially, protecting the steel beneath from rusting even if the zinc layer is scratched

Key terms in this question

galvanising

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