Metal Reactivity (WJEC GCSE Science (Double Award)): Revision Note

Metal Reactivity

The Reactivity Series

• Based on how they react with other substances, a reactivity series can be produced in which the metals are placed in order of their reactivity

• Metal atoms form positive ions by loss of electrons when they react with other substances

• The tendency of a metal to lose electrons is a measure of how reactive the metal is

• A metal that is high up on the series loses electrons easily and is thus more reactive than one which is lower down on the series

• Note that although carbon and hydrogen are non-metals, they are included in the series as they are useful in extracting metals from their oxides by reduction processes

The Reactivity Series

The reactivity of metals decreases going down the reactivity series

• A displacement reaction occurs when a more reactive metal will displace a less reactive metal from its compounds 

• This can occur by:

• Reacting a metal with a metal oxide (by heating)

  • Reacting a metal with an aqueous solution of a metal compound

• It is possible to reduce copper(II) oxide by heating it with zinc

  • The reducing agent in the reaction is zinc

Zn    +     CuO    →    ZnO    +    Cu

zinc + copper oxide → zinc oxide + copper

Metal Oxide Displacement Table

Thermite

• The thermite reaction is a highly exothermic reaction that occurs when iron(III) oxide is reacted with aluminium metal

• As aluminium is more reactive than iron, the iron in iron(III) oxide is displaced 

iron(III) oxide + aluminium → iron + aluminium oxide

Fe₂O₃ + 2Al → 2Fe + Al₂O₃

• The reaction releases so much heat that the iron formed is molten so this process is used in welding and incendiary devices

Displacement reactions between metals & aqueous solutions of metal salts

• The reactivity between two metals can be compared using displacement reactions in salt solutions of one of the metals

• This is easily seen as the more reactive metal slowly disappears from the solution, displacing the less reactive metal

• For example, magnesium is a reactive metal and can displace copper from a copper sulfate solution:

Mg + CuSO₄  →  MgSO₄ + Cu

• The blue colour of the CuSO₄ solution fades as colourless magnesium sulfate solution is formed.

• Copper coats the surface of the magnesium and also forms solid metal which falls to the bottom of the beaker

Diagram showing a displacement reaction

The colour of the solution changes when magnesium displaces copper from copper sulfate

Other displacement reactions

Metal Solutions Displacement Table