Key Terms
- Ore: Metal-containing rock worth extracting
- Reduction: Loss of oxygen from metal oxide
- Cryolite: Solvent that lowers melting point of Al₂O₃
- Bioleaching: Bacteria extract copper compounds
- Phytomining: Plants absorb copper; ash processed
Must-Know Facts
- More reactive than C → electrolysis (Al, Na, K)
- Less reactive than C → carbon reduction (Fe, Zn, Cu)
- Iron ore: haematite (Fe₂O₃) → blast furnace
- Aluminium ore: bauxite (Al₂O₃) + cryolite
- Cathode: Al³⁺ reduced → Al metal
- Anode: O²⁻ oxidised → O₂; anode burns away
Key Equations
- Fe₂O₃ + 3CO → 2Fe + 3CO₂ (carbon monoxide reduces iron oxide)
- Al³⁺ + 3e⁻ → Al (cathode reduction in electrolysis)
- 2O²⁻ → O₂ + 4e⁻ (anode oxidation in electrolysis)
- 2Al₂O₃ → 4Al + 3O₂ (overall electrolysis of aluminium oxide)
Common Mistakes
- Saying carbon can reduce aluminium oxide: Aluminium is more reactive than carbon — carbon cannot displace it; electrolysis is required
- Forgetting why cryolite is used: Cryolite lowers the melting point of aluminium oxide from ~2000°C to ~850°C, saving enormous amounts of energy
- Not explaining why the anode needs replacing: Oxygen produced at the anode reacts with the carbon anode forming CO₂, burning it away — anodes must be regularly replaced
- Confusing bioleaching and phytomining: Bioleaching uses bacteria to produce copper sulfate solution; phytomining uses plants that absorb copper, then the plants are burned and copper extracted from the ash
This topic summary covers Knowledge Organiser: Metal Extraction within Extracting Metals for GCSE Chemistry. Revise Extracting Metals in Chemical Changes for GCSE Chemistry with 6 exam-style questions and 6 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 14 of 14 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Extracting Metals
Which method is used to extract a metal that is MORE reactive than carbon?
Iron is extracted from haematite in a blast furnace. Describe how iron is obtained from iron oxide using carbon, and explain the term 'reduction' in this context.
Quick recall flashcards
Which metals must be extracted by electrolysis, and why?
Metals MORE reactive than carbon (e.g. aluminium, sodium, potassium) must be extracted by electrolysis. Carbon is not reactive enough to pull oxygen away from them.
What is haematite, and where is iron extracted from it?
Haematite is iron oxide (Fe₂O₃) — the main ore of iron. Iron is extracted from haematite in a blast furnace using carbon (coke) as the reducing agent.