Welcome to practical physicsPracticle physics - practical activities designed for use in the classroom with 11 to 19 year olds
 

Copper plating various metal objects

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


circuit

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.
 

Teaching notes


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 
 

Related guidance


Electric charge and current - a short history