Using materials

Rusting is a specific type of corrosion that affects only iron and alloys containing iron.

• •Both air (oxygen) and water must be present for iron to rust, forming hydrated iron(III) oxide.
• •Corrosion can be prevented using a physical barrier such as painting, greasing, or electroplating.
• •Aluminium resists corrosion because a protective thin layer of aluminium oxide forms on its surface.
• •Sacrificial protection attaches a more reactive metal (e.g. zinc or magnesium) to iron so it reacts with water and oxygen instead of the iron.
• •Galvanising coats iron in zinc, providing both a physical barrier and sacrificial protection if the surface is scratched.

Pure metals are often too soft for practical use, so they are mixed with other elements to increase strength.

• •Pure metals have regular layers of atoms that slide easily over each other, making them soft and malleable.
• •In an alloy, atoms of different sizes disrupt the regular layers, preventing them from sliding and making the alloy harder.

The properties of polymers, ceramics, and composites depend on their structure, components, and manufacturing conditions.

• •Soda-lime glass is made by heating sand, sodium carbonate, and limestone, whereas borosilicate glass (sand and boron trioxide) melts at higher temperatures.
• •Clay ceramics are made by shaping wet clay and heating it in a furnace, creating hard but brittle crystalline bonds.
• •Examples of composites include fibreglass, carbon fibre, concrete, and wood.