Specification Point 5.5 C:
Explain, using models, why converting pure metals into alloys often increases the strength of the product.
- Alloys are mixtures of metals where the metals are not chemically combined.
- They can be made from metals mixed with non-metals such as carbon.
- Alloys often have properties that can be very different from the metals they contain, for example they can have more strength, hardness or resistance to corrosion or extreme temperatures.
- Alloys contain atoms of different sizes, which distorts the regular arrangements of atoms.
- This makes it more difficult for the layers to slide over each other, so they are usually much harder and stronger than the pure metal.
Particle diagram showing the mixture of elements in an alloy
Specification Point 5.6C:
Explain why iron is alloyed with other metals to produce alloy steels.
- Molten iron is an alloy of 96% iron, with carbon, phosphorus, silicon and sulfur impurities.
- It is too brittle so most of it is converted into steel by removing some of the impurities.
- Not all of the carbon is removed as steel contains some carbon, the percentage of which depends on the use of the steel.
- Alloys of steel are made from adding other metals to steel such as chromium, manganese or nickel.
- By carefully controlling the amounts added, the particular type of alloy required can be produced.
- Steel alloys are used in construction, transport, manufacturing and other industries.
Diagram of a high carbon steel drill bit which is used for drilling through other metals
Edexcel GCSE Chemistry Notes
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