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Uses of metals

Aluminium, copper and gold are useful metals. The table shows common alloys that contain these metals.

AlloyComposition
MagnaliumAluminium and magnesium
BrassCopper and zinc
Jewellery goldGold and copper
AlloyMagnalium
CompositionAluminium and magnesium
AlloyBrass
CompositionCopper and zinc
AlloyJewellery gold
CompositionGold and copper

The uses of metals are related to their .

Aluminium and magnalium

Aluminium does not react with water. Its surface is protected by a natural layer of aluminium oxide that allows the metal to resist . Aluminium foil is used in the home for wrapping and storing food because it does not react to substances in food. It is , so it is easily folded into shape around the food.

Aluminium has a low , so pieces of aluminium are relatively lightweight. Magnalium is stronger than aluminium alone but still has a low density. It is used to make aircraft parts.

Question

Suggest an explanation for why aluminium is used to make overhead electricity cables.

Copper and brass

Copper and brass resist corrosion and are good electrical conductors. Copper is a better conductor than brass, and it is used in electrical wiring. Brass is stronger than copper, so it is used for the pins in electrical plugs.

Two electrical cables that have had the outer insulating layer removed, showing the internal cables
Image caption,
Electrical wires are protected by a tough layer of an insulating polymer

Gold

Gold is a very soft and malleable metal. It is also very , so it resists corrosion and stays shiny. The gold used for jewellery is gold alloyed with other metals, often copper. This makes the jewellery much stronger while keeping its ability to stay shiny.

Question

Suggest an explanation for why thin gold foil is used to decorate picture frames.