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Uses of metals and alloys
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How a metal is extracted depends on its reactivity. Its uses depend on its properties, and alloys improve those properties.
Extraction
Most metals are extracted from ores found in the Earth's crust.
Metals more reactive than carbon (such as aluminium) are extracted by electrolysis, which needs a lot of electrical energy.
Metals less reactive than carbon (such as iron) are extracted by heating with carbon, which reduces the oxide.
Very unreactive metals such as gold are found uncombined.
When given information about a process, comment on energy use, cost, raw materials and pollution.
Metals more reactive than carbon (such as aluminium) are extracted by electrolysis, which needs a lot of electrical energy.
Metals less reactive than carbon (such as iron) are extracted by heating with carbon, which reduces the oxide.
Very unreactive metals such as gold are found uncombined.
When given information about a process, comment on energy use, cost, raw materials and pollution.
Properties and uses
Alloys
An alloy is a mixture of a metal with one or more other elements.
In a pure metal, the atoms are all the same size and arranged in layers that slide easily.
In an alloy, different-sized atoms disrupt the layers, so they cannot slide as easily. Alloys are harder than pure metals.
Steel is an alloy of iron with carbon.
In a pure metal, the atoms are all the same size and arranged in layers that slide easily.
In an alloy, different-sized atoms disrupt the layers, so they cannot slide as easily. Alloys are harder than pure metals.
Steel is an alloy of iron with carbon.
Why is aluminium used for aircraft bodies rather than steel?
- Aircraft must be light.
- Aluminium has a low density.
- It also resists corrosion.
Answer: It has a low density and resists corrosion.
Metals above carbon are extracted by electrolysis; those below by heating with carbon. Aluminium: low density, corrosion resistant. Copper: excellent conductor. Steel: strong. Alloys are mixtures; different-sized atoms stop layers sliding, so alloys are harder.
The interactive lesson includes the diagrams for this topic.
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