Extraction and uses of metals
Edexcel International GCSE ChemistryΒ· 2.22Cβ2.27CΒ· 12 min read
1. Occurrence of Metals in the Earth's Crustβ β βββHigher onlyβ± 2 min
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Ore and Native Metal
Most metals are found as compounds in ores (naturally occurring rocks with sufficient metal content for economic extraction). Very unreactive metals are found as uncombined native elements.
The occurrence of a metal directly links to its position in the reactivity series. Highly reactive metals such as aluminium and magnesium readily react with oxygen and other elements in the crust to form stable compounds, so they are only found in ores. Unreactive metals like gold, silver and platinum do not easily form compounds, so they exist as pure native metals.
Explain why silver is found as a native element while calcium is only found in ores.
- 1
Silver is positioned very low in the reactivity series, meaning it is extremely unreactive.
- 2
Unreactive metals do not readily form compounds with elements in the Earth's crust, so they exist as pure native elements.
- 3
Calcium is very high in the reactivity series, so it readily reacts to form stable oxide and carbonate compounds in ores, and is never found as a pure native metal.
2. Extraction Methods and Reactivity Seriesβ β β ββHigher onlyβ± 3 min
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The method used to extract a pure metal from its ore depends on how reactive the metal is, as this determines how easily the metal compound can be reduced to the pure element.
Reactivity relative to carbon | Extraction method | Examples |
|---|---|---|
More reactive than carbon | Electrolysis of molten ore | Aluminium, magnesium, sodium |
Less reactive than carbon | Reduction with carbon or carbon monoxide | Iron, zinc, copper, lead |
Very unreactive | Minimal purification from native state | Gold, silver, platinum |
Tin is less reactive than carbon, while lithium is more reactive than carbon. State and justify the extraction method for each metal.
- 1
Lithium is more reactive than carbon, so carbon cannot remove oxygen from lithium oxide compounds.
- 2
Lithium must therefore be extracted using electrolysis of its molten ore.
- 3
Tin is less reactive than carbon, so carbon can reduce tin oxide to pure tin metal.
- 4
Tin is therefore extracted via reduction with carbon.
3. Uses of Aluminium, Copper and Ironβ β βββHigher onlyβ± 3 min
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The uses of common metals are directly linked to their physical and chemical properties. You are expected to recall the properties and uses of aluminium, copper, and three types of steel for the exam.
Metal/Steel Type | Key Properties | Common Uses |
|---|---|---|
Aluminium | Low density, good electrical conductor, forms protective corrosion-resistant oxide layer | Aeroplane parts, drink cans, overhead power cables |
Copper | Excellent electrical conductor, very malleable and ductile, resistant to corrosion | Electrical wiring, plumbing pipes, cookware |
Low-carbon (mild) steel | Soft, malleable, ductile, strong | Car bodies, bridge construction, general building materials |
High-carbon steel | Hard, brittle, resistant to wear | Cutting tools, knife blades, drill bits |
Stainless steel (alloy of Fe, Cr, Ni) | Hard, highly corrosion resistant | Cutlery, surgical instruments, kitchen sinks |
Explain why aluminium is used to make overhead power cables instead of copper.
- 1
Aluminium has a much lower density than copper, so overhead cables made from aluminium are significantly lighter.
- 2
Lighter cables reduce the load on supporting pylons, making installation cheaper and safer.
- 3
Aluminium also forms a thin protective oxide layer that prevents corrosion, so it lasts longer outdoors without maintenance.
4. Alloys: Structure and Hardnessβ β β ββHigher onlyβ± 3 min
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Alloy
A mixture of a metal with one or more other elements, usually other metals or carbon. Alloys are designed to have improved properties compared to pure metals.
Pure metals have a regular lattice structure made of identical atoms. When force is applied, layers of atoms can slide easily over each other, making pure metals soft and malleable. Alloys contain atoms of different sizes from the added elements, which disrupt the regular arrangement of the metal lattice. This means the layers of atoms cannot slide past each other easily, so alloys are much harder than pure metals.
Explain why bronze (an alloy of copper and tin) is harder than pure copper.
- 1
Pure copper has a regular lattice structure of identical copper atoms. Layers of atoms can slide easily over each other when force is applied, making pure copper soft.
- 2
Bronze contains tin atoms which are a different size to copper atoms, disrupting the regular lattice arrangement of copper atoms.
- 3
This disruption prevents the layers of atoms from sliding past each other easily, making bronze much harder than pure copper.
5. Common Pitfalls
Wrong move:
Stating all metals are extracted via carbon reduction
Why:
Metals more reactive than carbon (e.g. aluminium, sodium) cannot be reduced by carbon, and require electrolysis instead.
Correct move:
Always check the metal's position relative to carbon in the reactivity series to select the correct extraction method.
Wrong move:
Explaining alloy hardness by stating the added elements are harder
Why:
The required marking point refers to disruption of the regular atomic lattice, not the inherent hardness of the added elements.
Correct move:
Explicitly state that different sized atoms disrupt the regular lattice layers, preventing them from sliding easily.
Wrong move:
Confusing low-carbon and high-carbon steel uses
Why:
Low-carbon (mild) steel is soft and malleable, while high-carbon steel is hard and brittle, so their uses are opposite for most applications.
Correct move:
Link steel properties directly to use: soft/malleable = car bodies/construction, hard/brittle = cutting tools/blades.
Wrong move:
Memorising detailed extraction processes (e.g. blast furnace reactions)
Why:
The specification explicitly states detailed process knowledge is not required, all relevant process data is provided in exam questions.
Correct move:
Focus only on recalling the extraction method (carbon reduction vs electrolysis) based on reactivity relative to carbon.
Wrong move:
Stating aluminium is used because it is unreactive
Why:
Aluminium is actually very reactive, but it forms a thin, protective layer of aluminium oxide that prevents further corrosion.
Correct move:
Reference the protective oxide layer when explaining aluminium's corrosion resistance for exam answers.
6. Quick Reference Cheatsheet
Key Concept | Exam Recall Point |
|---|---|
Metal Occurrence | Unreactive metals = native state; reactive metals = ores |
Extraction Rule | Above carbon = electrolysis; below carbon = carbon reduction |
Aluminium Uses | Low density + corrosion resistance: planes, cans, power cables |
Copper Uses | Good conductivity + malleability: wiring, plumbing |
Steel Types | Low C (soft: car bodies), High C (hard: tools), Stainless (corrosion resistant: cutlery) |
Alloy Hardness | Different sized atoms disrupt lattice layers β no sliding β harder |
Going deeper
What's Next
Now that you have mastered the core content on extraction and uses of metals, you are ready to apply this knowledge to Edexcel IGCSE Chemistry Paper 2C exam questions. This topic is frequently tested alongside reactivity series questions, so ensure you can quickly link a metal's position in the series to its extraction method and properties before attempting past papers. You can also revisit metallic bonding and electrolysis basics to reinforce your understanding of the underlying principles behind extraction and alloy structure. Remember this entire sub-topic is exclusive to the Chemistry-only Paper 2C, so prioritize these recall points if you are sitting the 4CH1 exam.