Uses of metals Revision Notes

Aluminium is a metal with a low density of approximately 2.7 g/cm³, which is about one-third the density of iron (7.9 g/cm³). This low density means aluminium is lightweight, reducing the overall mass of structures made from it.

In aircraft production, weight reduction is critical to improve fuel efficiency and flight performance. Using aluminium alloys, which combine aluminium with small amounts of other metals to improve strength, allows aircraft to be strong yet light.

The physical property of low density combined with adequate strength makes aluminium ideal for aircraft frames and body panels.

• Density of aluminium ≈ 2.7 g/cm³, much less than iron or steel.
• Lightweight materials reduce fuel consumption in aircraft.
• Aluminium alloys provide strength and corrosion resistance needed for aircraft parts.

Overhead power lines require materials that can support their own weight over long distances and conduct electricity efficiently.

Aluminium's low density reduces the mechanical load on pylons and supports, allowing longer spans between supports and reducing infrastructure costs.

Although aluminium's electrical conductivity (about 60% that of copper) is lower than copper, its low density means that aluminium wires of the same weight have a larger cross-sectional area, compensating for conductivity loss and allowing efficient current flow.

• Aluminium has good electrical conductivity (~60% of copper).
• Low density allows longer spans in overhead cables due to reduced weight.
• Aluminium wires are often reinforced with steel cores for strength.

Aluminium forms a thin, protective oxide layer (Al₂O₃) on its surface when exposed to air, which prevents further oxidation and corrosion.

This corrosion resistance makes aluminium suitable for food packaging such as foil and cans, as it does not react with food or degrade easily.

The impermeability of aluminium foil to light, oxygen, and moisture helps preserve food quality and extends shelf life.

• Protective aluminium oxide layer prevents corrosion.
• Non-toxic and does not react with most foods.
• Aluminium foil is impermeable to gases and moisture, preserving food.

Copper is an excellent conductor of electricity, with conductivity higher than aluminium, making it ideal for electrical wiring where efficient current flow is essential.

Copper is also ductile and flexible, allowing wires to be bent and shaped without breaking, which is important for installation in buildings and electronic devices.

Its resistance to corrosion ensures long-lasting electrical connections and safety.

• Copper has very high electrical conductivity (about 59.6 × 10⁶ S/m).
• Ductility allows wires to be drawn into thin, flexible cables.
• Corrosion resistance ensures durability of electrical wiring.