CHEMISTRY · Stage 9 · Chapter 12: Chemical Reactions 3 and Rates

Chemistry 12.3 Metal displacement reactions — Aqueous and Thermite Displacements

5 min read 7 parts Lesson 3 of 13

0%read

Lesson summary

12.3 Metal displacement reactions — Aqueous and Thermite Displacements — Alhussan International Academy — Chemistry (Stages 7–9) notes: Define a metal displacement reaction and predict displacement in solutions, with metal oxides and in the thermite reaction.Metal displacement re…

Reactivity series
Types of reaction
Magnesium and copper oxide
Conclusion
Zinc and copper sulfate
Magnesium and copper sulfate

Part 1 of 7Displacement reactions

1Metal displacement reaction

= a reaction in which a more reactive metal displaces (pushes out) a less reactive metal from its compound.

2Reactivity series1 point

— it lists metals in order of how vigorously they react; calcium is near the top and gold at the bottom is inert.

Part of the series: calcium, magnesium, aluminium, zinc, iron, copper, silver, gold.

3Types of reaction

— combustion, corrosion and precipitation are other types, and displacement is another.

4Rule1 point

— displacement happens when the metal on its own is higher in the reactivity series than the metal in the compound.

If the metal on its own is less reactive, there is no reaction.

Part 2 of 7Displacement with metal oxides

1Thermite reaction3 points

— aluminium + iron oxide → aluminium oxide + iron.

A worker uses it to make liquid iron, which cools and freezes to join railway lines together.
It is intensely exothermic, reaching temperatures above 2000 °C, so the iron forms as a white-hot liquid.
It needs a high temperature to start, such as from a magnesium fuse, and then releases enough energy to continue itself.

2Magnesium and copper oxide1 point

— magnesium + copper oxide → magnesium oxide + copper.

In a particle diagram, magnesium atoms take the oxygen and copper atoms are left.

Part 3 of 7Alex's investigation with oxides

Metal	Metal oxide	Observations
Iron	Copper oxide	Glows red, pink-brown metal formed
Copper	Iron oxide	No reaction
Zinc	Copper oxide	Glows red, pink-brown metal formed
Copper	Zinc oxide	No reaction
Zinc	Iron oxide	Glows red, silver-coloured metal formed

Equations — iron + copper oxide → iron oxide + copper; zinc + copper oxide → zinc oxide + copper; zinc + iron oxide → zinc oxide + iron.
Conclusion — displacement reactions happen when the metal on its own is higher in the reactivity series than the metal in the compound.

Part 4 of 7Displacement in solution

Zinc and copper sulfate — zinc dissolves, brown-red copper forms on it and the blue colour fades as colourless zinc sulfate forms.
- zinc + copper sulfate → zinc sulfate + copper.
- Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s).
Magnesium and copper sulfate — blue solution goes paler and copper metal forms: magnesium + copper sulfate → magnesium sulfate + copper.
Iron and copper sulfate — iron displaces copper from copper sulfate solution.
No reaction — copper added to magnesium chloride or zinc sulfate does nothing, because copper is less reactive and cannot displace magnesium or zinc.

Part 5 of 7Ionic explanation

Electron transfer — zinc atoms lose electrons to become Zn²⁺ ions, and copper ions gain these electrons to become copper atoms.
- Zn → Zn²⁺ + 2e^- and Cu²⁺ + 2e^- → Cu.
Spectator ions — the sulfate ions are unchanged.
More reactive metal — it is the one that forms ions more readily.
Energy — the reaction is exothermic, so the solution warms slightly.

Part 6 of 7Predicting reactions

Metal	Compound	Reaction?
Magnesium	Copper sulfate	Yes
Iron	Zinc sulfate	No
Zinc	Iron oxide	Yes (on strong heating)
Copper	Aluminium oxide	No

Part 7 of 7Building a reactivity series from evidence

Grid of results — add each metal to solutions of the others' compounds and record ticks and crosses.
- A metal that displaces every other metal is at the top, and one that displaces none is at the bottom.
Evidence of reaction — a colour change in the solution, a deposit of solid metal, bubbles of gas or a temperature rise.
Fair test — use the same volume and concentration of solution, the same size of metal strip and the same starting temperature.
Safety — wear eye protection and carry out thermite only as a teacher demonstration because the heat is extreme and sparks are thrown out.
Conclusion — name the order of reactivity, quote the evidence and state limits such as only a few metals being tested.

Last updated: 13 October 2026