Electricity and Magnetism

Copper plating various metal objects

Practical Activity for 14-16 PRACTICAL PHYISCS

Class practical

A useful application of electrolysis.

Apparatus and Materials

For each student group

  • Cells, 1.5 V, with holders, 3
  • Lamps with holders, 2
  • Crocodile clips, 2
  • Ammeter (0 - 1 amp), DC
  • Leads, 4 mm, 7
  • Beaker, 250 ml
  • Strip of copper foil, 1 cm wide
  • Copper sulfate solution, 0.5 M
  • Coin or other object to be plated
  • Silver nitrate plating solution (see technical notes)

Health & Safety and Technical Notes

Read our standard health & safety guidance


To make the silver nitrate plating solution dissolve 1.6 g of silver nitrate and 32 g of potassium iodide in 100 ml of distilled water. Add 3 drops of concentrated sulphuric acid.

The strip of copper foil should be 2 cm longer than the depth of the beaker.

Procedure

  1. Fit the strip of copper foil inside the beaker as shown, with the top 2 cm bent back over the edge of the beaker.
  2. Use one crocodile clip to keep the foil in place.
  3. Attach a second crocodile clip to a coin, and dangle the coin in the beaker at the opposite side to the copper foil. Ensure that the coin is attached to the negative terminal.
  4. Connect leads to the clips.
  5. Half-fill the beaker with copper sulfate solution.
  6. Complete the circuit as shown. Let the current run for some minutes and then look at the coin and the copper strip to see if there are any differences.
  7. Repeat with coins made of different metals.

Teaching Notes

  • Avoid objects made of zinc or iron - these metals displace copper of their own accord from the solution and so can confuse the story badly. Try the materials yourself beforehand.
  • Copper-plating coins is a useful way to use up small change from foreign travel. Some students will want to see what happens to ‘silver coins’, and after a ‘disaster’ in copper sulfate solution, a little silver nitrate solution (expensive!) can be tried.
  • An old iron bedstead thrown into a river with copper salts in it proves to be an easy way of getting at the copper. Nickel-plated iron will also show this substitution.

This experiment was safety-tested in June 2007

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