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Year 11 - Science

Electrolysis: purifying copper

Electrolysis

Unit Summary

This unit focuses on electrolysis, electrode reactions, and predicting products, including competing reactions in solutions. It explains metal extraction through electrolysis and writing ionic equations. It also covers tests for gases like oxygen, hydrogen, carbon dioxide, and chlorine.

Lesson Summary

You will learn to investigate what happens when a solution of copper sulfate is electrolysed with copper electrodes.

Key Notes

  • Purification of copper involves using copper electrodes in an electrolyte.
  • The electrolyte must contain the same ions, in solution, as the metal being purified by electrolysis.
  • Measuring the mass change in the copper electrodes demonstrates the transfer of copper.
  • Impurities in the anode do not transfer to the cathode, leading to pure copper deposition.
  • Other uses for this technique include electroplating, where you would use multiple metals e.g. gold.

Vocabulary To Learn

  • pure: a single element or compound that is not mixed with any other substance
  • anode: a positively charged electrode, in an electrolysis cell, to which the anions are attracted
  • cathode: a negatively charged electrode, in an electrolysis cell, to which the cations are attracted
  • electrolyte: a liquid or an aqueous salt solution that contains freely moving ions
  • electroplating: a process that uses electricity to deposit a thin layer of metal onto the surface of another conductive object

Common Mistakes To Avoid

  • Pupils do not always appreciate the difference between using inert carbon electrodes and metal electrodes, which will take part in the reaction.

3 Quick Questions (With Answers)

1. Explain the scientific idea in this lesson using two key points.

Purification of copper involves using copper electrodes in an electrolyte. The electrolyte must contain the same ions, in solution, as the metal being purified by electrolysis.

2. Define this scientific word and use it in context. 'pure'

a single element or compound that is not mixed with any other substance. Include the word in a full scientific explanation, not as a single label.

3. Correct this common scientific misunderstanding.

Mistake: Pupils do not always appreciate the difference between using inert carbon electrodes and metal electrodes, which will take part in the reaction. Correction: Provide pupils with the opportunity to investigate the electrolysis of copper sulfate with both inert electrodes and with copper electrodes and then compare the results.

More Lessons In This Unit

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