Demonstration

Copper(II) oxide  reacts with magnesium, demonstrating the ability of magnesium to remove oxygen from an oxide of copper, and hence the relative positions of copper and magnesium in the reactivity series.

Lesson organisation

This demonstration activity should take about 20 mins. The reaction is violent but safe, provided the procedure is followed exactly. A rehearsal is essential if this experiment has not been done before.

Apparatus Chemicals

Eye protection for students

Goggles or face shield for teacher

Safety screens

Crucible (Note 1)

Pipeclay triangle

Tripod

Bunsen burner

Large sheet of hardboard to protect the bench (or heat resistant mats)

Scrap paper, 2 pieces

Magnesium powder (HIGHLY FLAMMABLE), 0.25 g (Note 2)

Copper(II) oxide powder (HARMFUL, DANGEROUS FOR THE ENVIRONMENT), 0.25 g (Note 2)

Refer to Health & Safety and Technical notes section below for additional information.

Health & Safety and Technical notes

Read our standard health & safety guidance

Wear goggles or a face shield and use safety screens. Ensure students are wearing eye protection throughout the demonstration.

Magnesium powder, Mg(s), (HIGHLY FLAMMABLE) - see CLEAPSS Hazcard.

Copper(II) oxide, CuO(s), (HARMFUL, DANGEROUS FOR THE ENVIRONMENT) - see CLEAPSS Hazcard

1 Use a metal crucible rather than a ceramic one. Alternatively, use a steel ‘crown’ bottle top which has had the plastic insert burnt out (in a fume cupboard) - the bottle top must NOT be hot when the magnesium powder/copper oxide mix is added.

2 These amounts must not be exceeded unless you are covered by an Explosives Certificate issued by the police, in line with UK Explosives Regulations 2014.

Procedure

a Protect the bench with a large sheet of hardboard or heat resistant mats.

b Set up a tripod with a pipe clay triangle and a crucible. Place safety screens around the apparatus.

c Place the Bunsen burner under the crucible.

d Move the class to the back of the room, with the safety screen between them and the experiment. They should wear safety glasses. Warn them not to stare at the crucible.

e Gently mix the small portions of magnesium and copper(II) oxide by putting them on a piece of scrap paper and repeatedly pouring back and forth onto another piece of scrap paper. Add the mixture to the crucible.

f Light the Bunsen burner (away from the crucible) with the air hole open and then place the Bunsen flame under the crucible. Move quickly to a metre or two in front of the safety screen.

f After one or two minutes (be patient!) a vigorous reaction occurs. Do not stare at the crucible as the flash is bright.

g If nothing happens, do not return to the apparatus but leave it for up to 15 mins. Then turn off the gas at the stop-cock, allow the apparatus to cool and then place the crucible and contents in a large beaker of water.

h Do not be tempted to use other metal oxides.

Teaching notes

The reaction is:

Copper oxide + magnesium → copper + magnesium oxide

This shows that magnesium is higher in the reactivity series than copper.

Most of the products are vaporised in the above reaction.

Health & Safety checked, August 2016

Credits

This Practical Chemistry resource was developed by the Nuffield Foundation and the Royal Society of Chemistry.

© Nuffield Foundation and the Royal Society of Chemistry

Page last updated September 2016