How reactive are metals, and how are they extracted from their ores?
The reactivity series, displacement reactions, oxidation and reduction, the extraction of metals by reduction with carbon or electrolysis, and the link between reactivity and extraction method.
A focused answer to Edexcel GCSE Combined Science Topics 3 and 4 (CC3 to CC4), covering the reactivity series, displacement reactions, oxidation and reduction, and how metals are extracted from their ores by reduction with carbon or by electrolysis.
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What this dot point is asking
Edexcel wants you to use the reactivity series, explain displacement reactions, define oxidation and reduction, and explain how metals are extracted from their ores by reduction with carbon or by electrolysis, linking the method to the metal's reactivity.
The reactivity series
Displacement reactions
A more reactive metal will displace a less reactive metal from its compound (its salt solution or oxide). For example, magnesium displaces copper from copper sulfate:
Oxidation and reduction
Extracting metals
How a metal is extracted from its ore depends on its position in the reactivity series compared with carbon.
- Metals less reactive than carbon (zinc, iron, copper, and so on) can be extracted by reduction with carbon: heating the metal oxide with carbon removes the oxygen. For example, iron oxide is reduced in a blast furnace.
- Metals more reactive than carbon (aluminium and above) cannot be extracted with carbon, because carbon is not reactive enough to remove the oxygen. They are extracted by electrolysis of the molten compound, which uses a lot of electrical energy and is therefore expensive.
This is also why very unreactive metals such as gold are found native (as the metal itself) in the ground and need no chemical extraction.
The reactivity series also predicts how metals react with water and acid: the most reactive metals (potassium, sodium) react vigorously with cold water, magnesium reacts slowly with water but readily with acid, and the least reactive metals (copper, gold) do not react with water or dilute acid at all. A more reactive metal also reacts more vigorously when it does react, for example fizzing faster with acid as it releases hydrogen. Recognising these patterns lets you place an unknown metal in the series from how it behaves.
Try this
Q1. Define oxidation in terms of electrons. [1 mark]
- Cue. The loss of electrons.
Q2. Explain why aluminium is extracted by electrolysis rather than with carbon. [2 marks]
- Cue. Aluminium is more reactive than carbon, so carbon cannot remove the oxygen from its ore.
Exam-style practice questions
Practice questions written in the style of Pearson Edexcel exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Edexcel 20204 marksIron is extracted from iron oxide by heating with carbon, but aluminium is extracted from its ore by electrolysis. Explain why the two metals are extracted by different methods.Show worked answer →
A 4-mark explain question linking reactivity to extraction.
A metal less reactive than carbon, such as iron, can be extracted by heating its oxide with carbon, because the carbon removes the oxygen (reduces the oxide) (2 marks). Aluminium is more reactive than carbon, so carbon cannot remove the oxygen from its ore (1 mark). Therefore aluminium must be extracted by electrolysis, which can separate even strongly held ions, although this uses a lot of energy and is expensive (1 mark).
Markers reward the carbon-reduction rule for metals below carbon, and the need for electrolysis for metals above carbon, with the energy or cost point.
Edexcel 20223 marksMagnesium is added to copper sulfate solution and a displacement reaction occurs. Explain why magnesium displaces copper, and state which substance is oxidised.Show worked answer →
A 3-mark displacement and redox question.
Magnesium is more reactive than copper, so it displaces copper from the copper sulfate solution, forming magnesium sulfate and copper metal (1 mark). Magnesium is oxidised because it loses electrons (to form magnesium ions) (1 mark); the copper ions are reduced because they gain electrons (to form copper metal) (1 mark).
Markers reward the more reactive metal displacing the less reactive one, and correctly identifying magnesium as oxidised (loss of electrons).
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Sources & how we know this
- Edexcel GCSE (9-1) Combined Science (1SC0) specification — Pearson (2016)