GCSE Chemistry revision

Alloys as useful materials

Using materials (chemistry only)

AQA 4.10.3.2 Foundation & Higher

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Bronze (an alloy of copper and tin) is tough and highly resistant to corrosion, making it ideal for marine hardware, propellers, and statues; Brass (an alloy of copper and zinc) is malleable with low friction, making it suitable for musical instruments, plumbing taps, and door fittings.
Example: Ship propellers are cast from bronze to resist corrosion in saltwater, whereas trumpet valves and door locks use brass for its smooth, low-friction operation.

1. Copper Alloys (Bronze and Brass) AQA

Bronze (an alloy of copper and tin) is tough and highly resistant to corrosion, making it ideal for marine hardware, propellers, and statues; Brass (an alloy of copper and zinc) is malleable with low friction, making it suitable for musical instruments, plumbing taps, and door fittings.
Example: Ship propellers are cast from bronze to resist corrosion in saltwater, whereas trumpet valves and door locks use brass for its smooth, low-friction operation.

Pure gold (24-karat) is too soft to maintain its shape in everyday items, so it is alloyed with copper, silver, and zinc to increase its hardness and resistance to wear.
Example: 18-karat gold contains 75% pure gold mixed with 25% copper and silver, making it durable enough for everyday jewellery like engagement rings without scratching easily.

2. Gold Alloys AQA

Pure gold (24-karat) is too soft to maintain its shape in everyday items, so it is alloyed with copper, silver, and zinc to increase its hardness and resistance to wear.
Example: 18-karat gold contains 75% pure gold mixed with 25% copper and silver, making it durable enough for everyday jewellery like engagement rings without scratching easily.

High-carbon steel is hard but brittle, low-carbon steel is soft and easily shaped, and stainless steel (iron alloyed with chromium and nickel) is hard and highly resistant to rust.
Example: Drill bits and chisel blades are made from high-carbon steel to stay sharp, car bodies use low-carbon steel for ease of molding, and medical scalpels use stainless steel to withstand sterilization without rusting.

3. Steel Alloys (Iron Alloys) AQA

High-carbon steel is hard but brittle, low-carbon steel is soft and easily shaped, and stainless steel (iron alloyed with chromium and nickel) is hard and highly resistant to rust.
Example: Drill bits and chisel blades are made from high-carbon steel to stay sharp, car bodies use low-carbon steel for ease of molding, and medical scalpels use stainless steel to withstand sterilization without rusting.

Pure aluminium is lightweight but relatively soft; alloying it with elements such as magnesium or silicon creates materials with high tensile strength while retaining low density.
Example: Aircraft fuselages and frames are constructed from high-strength aluminium alloys to minimize total mass while enduring structural flight stress.

4. Aluminium Alloys AQA

Pure aluminium is lightweight but relatively soft; alloying it with elements such as magnesium or silicon creates materials with high tensile strength while retaining low density.
Example: Aircraft fuselages and frames are constructed from high-strength aluminium alloys to minimize total mass while enduring structural flight stress.

Alloys are harder than pure metals because the addition of different-sized atoms disrupts the regular, layered arrangement of the metal lattice, preventing the layers from easily sliding over one another when force is applied.
Example: Adding carbon atoms into the regular lattice of pure iron disrupts the rows of iron atoms, preventing them from slipping and resulting in a much stronger material.

5. Atomic Structure and Hardness AQA

Alloys are harder than pure metals because the addition of different-sized atoms disrupts the regular, layered arrangement of the metal lattice, preventing the layers from easily sliding over one another when force is applied.
Example: Adding carbon atoms into the regular lattice of pure iron disrupts the rows of iron atoms, preventing them from slipping and resulting in a much stronger material.