# Extraction of Metals

> CIE IGCSE Chemistry · 0620 2026-2028
> Source: https://www.owlsprep.com/study/cie-0620-u9-extraction-of-metals/

This guide covers core and extended content for CIE IGCSE Chemistry 0620 Unit 9: Extraction of Metals, linking extraction methods to the reactivity series and walking through key industrial processes.

**Prerequisites:** [Reactivity series of metals](https://www.owlsprep.com/study/cie-0620-u9-reactivity-series/); [Basics of electrolysis and redox reactions](https://www.owlsprep.com/study/cie-0620-u5-electrolysis/)

## Learning objectives

- Link metal extraction method to position in the reactivity series
- Describe core extraction processes for iron and aluminium
- Write half equations and redox statements for extraction (Extended only)
- Explain the role of key raw materials in industrial extraction processes
- Avoid common exam pitfalls in extraction-response questions

## 1. Extraction Method and Reactivity Series

**Ore** — A naturally occurring rock containing sufficient metal compound to make extraction of the metal economically viable.

The method used to extract a metal from its ore depends entirely on its position in the reactivity series. Less reactive metals can be extracted with simple physical purification, moderately reactive metals by reduction with carbon, and highly reactive metals by electrolysis of their molten ores.

- Metals below copper (e.g. gold, silver): found native (uncombined), require only physical purification
- Metals between zinc and copper: reduced by heating with carbon or carbon monoxide
- Metals above zinc (e.g. aluminium, magnesium, sodium): require electrolysis of molten compounds, as carbon cannot displace them

**Worked example:** Metal X does not react with dilute acids and is found uncombined in rock deposits. State the appropriate extraction method for X, and justify your answer.

1. First, identify the position of X in the reactivity series: if X does not react with dilute acids and is found native, it is less reactive than copper.
2. No chemical reaction is needed to separate X from impurities.
3. Correct method: Physical purification (e.g. washing, filtering to remove gangue from native metal particles).

> **Exam tip:** Always explicitly link extraction method justifications to the metal's position in the reactivity series to earn full marks.

## 2. Extraction of Iron (Core)

Iron is extracted from its ore haematite ($Fe_2O_3$) in a blast furnace, using four key raw materials: haematite, coke (impure carbon), limestone ($CaCO_3$), and hot compressed air.

1. Hot air is blown into the furnace base, burning coke to form carbon dioxide: $C + O_2 \rightarrow CO_2$. This exothermic reaction heats the furnace to ~1500°C.
2. Carbon dioxide reacts with hot coke to form carbon monoxide (the reducing agent): $CO_2 + C \rightarrow 2CO$
3. Carbon monoxide reduces iron(III) oxide to molten iron, which sinks to the furnace base: $Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2$
4. Limestone decomposes to form calcium oxide: $CaCO_3 \rightarrow CaO + CO_2$, which reacts with acidic silica impurities to form molten slag ($CaSiO_3$) that floats on iron and is tapped off.

**Worked example:** Name the reducing agent in the blast furnace, and write the balanced chemical equation for the reaction that produces pure iron from haematite.

1. The active reducing agent at operating furnace temperature is carbon monoxide, not solid carbon.
2. $$Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2$$
3. Check that all atoms are balanced on both sides of the equation to earn full marks.

## 3. Extraction of Aluminium (Core)

Aluminium is more reactive than carbon, so it is extracted by electrolysis of molten aluminium oxide obtained from the ore bauxite. Pure aluminium oxide has a very high melting point (~2000°C), so it is mixed with cryolite to lower the melting point to ~900°C, cutting energy costs significantly.

- Cathode (negative carbon lining): Al³+ ions gain electrons to form molten aluminium, which sinks to the cell base and is tapped off: $Al^{3+} + 3e^- \rightarrow Al$
- Anode (positive carbon electrodes): Oxide ions lose electrons to form oxygen gas: $2O^{2-} \rightarrow O_2 + 4e^-$
- Carbon anodes are replaced regularly, as hot oxygen reacts with carbon to form carbon dioxide, wearing away the electrodes.

**Worked example:** Explain why cryolite is added to aluminium oxide in the electrolytic extraction of aluminium.

1. Pure aluminium oxide has a melting point of ~2000°C, which would require very large amounts of energy to melt, making extraction prohibitively expensive.
2. Cryolite acts as a solvent, dissolving aluminium oxide and lowering the mixture's melting point to ~900°C, reducing energy costs for the process.

## Common pitfalls

- **Wrong:** Stating carbon is the reducing agent in the blast furnace
  - Why it fails: The active reducing agent at operating furnace temperature is carbon monoxide, not solid carbon
  - Correct: Explicitly name carbon monoxide as the reducing agent, linking to its reaction with haematite
- **Wrong:** Referring to electrolysis of aqueous aluminium oxide
  - Why it fails: Aqueous solutions contain H+ ions that are discharged instead of Al³+ ions, producing hydrogen not aluminium
  - Correct: Specify molten aluminium oxide (mixed with cryolite) is used for electrolysis
- **Wrong:** Only stating cryolite lowers melting point, no further justification
  - Why it fails: Exam questions require linking the lower melting point to reduced energy costs to earn full marks
  - Correct: Explain cryolite reduces energy costs by lowering the melting point of the aluminium oxide mixture
- **Wrong:** Writing anode half equations for oxygen production with electrons on the reactant side
  - Why it fails: Oxidation is loss of electrons, so electrons should appear on the product side of the half equation
  - Correct: Write the anode half equation as $2O^{2-} \rightarrow O_2 + 4e^-$
- **Wrong:** Stating all metals above copper are extracted by electrolysis
  - Why it fails: Metals between zinc and copper are extracted by reduction with carbon; only metals above zinc require electrolysis
  - Correct: Always link extraction method to the exact position of the metal in the reactivity series

## Cheatsheet

| Metal | Ore | Extraction Method | Key Reaction |
| --- | --- | --- | --- |
| Iron | Haematite ($Fe_2O_3$) | Reduction with CO in blast furnace | $Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2$ |
| Aluminium | Bauxite ($Al_2O_3$) | Electrolysis of molten oxide + cryolite | $2Al_2O_3 \rightarrow 4Al + 3O_2$ |
| Gold/Silver | Native uncombined | Physical purification | No chemical reaction required |

## What's next

Now that you have mastered metal extraction for CIE IGCSE Chemistry 0620, move on to related topics that frequently appear alongside extraction questions in exams. Next, revise the uses of metals and alloys, as exam questions often link extraction methods to the properties and real-world applications of the metals produced. Extended tier candidates should practice writing the ionic half-equations for the electrode reactions in aluminium extraction, and the symbol equations for iron extraction, to answer full extended-response questions. You should also review the environmental impacts of industrial extraction, such as the effect of carbon dioxide emissions from the blast furnace, a common synoptic question topic.

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