The real reactivity of aluminium
Class practical or Demonstration
This experiment illustrates the
displacement of copper from copper(II) sulfate solution using aluminium foil. Students add aluminium cooking foil to copper(II) sulfate solution and observe no reaction. Then sodium chloride is added and dissolved. A vigorous displacement reaction occurs and the solution gets very hot, aluminium dissolves and red copper is visible.
This class practical can take about 30 minutes to complete A flexicam would work well if this is to be done as a demonstration and allow students a clearer view of what is going on.
Wear eye protection
Conical flask (100 cm
Aluminium foil, 2 cm x 2 cm
Copper(II) sulfate solution 0.8 M (HARMFUL), 20 cm3
Sodium chloride, 2-3 g
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 and disposable nitrile gloves.
Aluminium foil, Al(s) - see CLEAPSS Hazcard.
4(aq), 0.8 M (HARMFUL, DANGEROUS FOR THE ENVIRONMENT) - see CLEAPSS Hazcard and CLEAPSS Recipe Book.
Sodium chloride, NaCl(s), (table salt)
1 Ensure the aluminium foil is completely consumed by the reaction before disposal to prevent a continued exothermic reaction in the rubbish bin. Use plenty of copper(II) sulfate solution and sodium chloride to ensure a complete reaction.
a Measure approximately 20 cm
3of copper(II) sulfate solution into the conical flask.
b Add a square of aluminium foil.
c Look for signs of a reaction.
d Add a spatula of sodium chloride and stir to dissolve.
e Observe any changes. If nothing happens, add more sodium chloride. Has displacement of copper from copper(II) sulfate occurred?
Student questions and example table.
1. Before the sodium chloride is added, does any reaction occur?
2. After adding sodium chloride, does the aluminium appear more or less reactive?
3. How does the salt affect this change?
Write yes or no.
Before the sodium chloride is added
After the sodium chloride is added
Aluminium does not show its true reactivity until the oxide layer is disturbed. Sodum chloride disturbs this oxide layer. Scratches on the surface of the oxide layer allow chloride ions to react with aluminium, this effects the cohesiveness of the oxide layer. This allows reaction with the copper(II) sulfate. Remind students what copper looks like, so that they know what they are looking for.
1. Aluminium appears less reactive than copper. The aluminium foil appears unable to displace copper from copper(II) sulfate solution.
2. Now aluminium is more reactive because it displaces copper. Aluminium + copper(II) sulfate
copper + aluminium sulfate
3. Scratches on the surface of the oxide layer allow chloride ions to react with aluminium, this effects the cohesiveness of the oxide layer. This allows a simple exchange reaction with the copper(II) sulfate. The protective oxide layer forms instantly the aluminium is exposed to the air.
Health & Safety checked, 2016
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 October 2015