Copper plating various metal objects
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
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.
a Fit the strip of copper foil inside the beaker as shown, with the top 2 cm bent back over the edge of the beaker.
b Use one crocodile clip to keep the foil in place.
c 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.
d Connect leads to the clips.
e Half-fill the beaker with copper sulfate solution.
f 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.
e Repeat with coins made of different metals.
1 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.
2 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