10 3 using materials

Rust is the hydrated iron(III) oxide that forms on iron when it corrodes.

Rusting specifically refer to the corrosion of iron.

The word equation for the rusting of iron is: iron + water + oxygen ⟶ hydrated iron(III)oxide

Two conditions needed for rusting of iron to occur are water and oxygen.

Examples of barrier methods that can prevent rusting are:

Nail A will rust because it is exposed to oxygen AND water.

True. Rusting weakens the structure and integrity of iron over time as more iron is lost.

False. Galvanising is the method of coating iron with a layer of zinc.

Sacrificial protection is when a more reactive metal is intentionally allowed to corrode to protect the metal it is covering.

Zinc is used to protect iron from corrosion because it is more reactive than iron so will react more readily with oxygen.

False. A metal more reactive than iron can be used for galvanising.

An alloy is a mixture of metals, where the metals are mixed together physically but are not chemically combined.

True. Alloys can also be made from metals mixed with non-metals such as carbon.

Alloys contain atoms of different sizes which distort the regular arrangement of atoms.

The increased hardness and strength of an alloy is caused by the different size atoms which distort the regular arrangements of atoms, preventing the layers from sliding over each other easily.

Advantages of using alloys over pure metals are:

False. Alloys are physical mixtures of metals, where the metals are not chemically combined.

Alloys often have greater strength / hardness, or resistance to corrosion / extreme temperatures compared to pure metals.

Uses of stainless steel include:

Low carbon steel can be used to make car bodies because it is soft and malleable.

The two main elements in steel alloys are iron and carbon.

False. Brass is an alloy of copper and zinc.

Bronze is an alloy of copper and tin.

High carbon steel is used to make cutting tools because it is very hard.

True. Carats are used to express the purity of gold jewellery.

Pure gold is not used to make jewellery because it is too soft.

Thermosetting polymers have high melting points because there are strong cross-links between polymer chains that need lots of energy to overcome.

The monomer used to produce high density and low density poly(ethene) is ethene.

High density and low density poly(ethene) have different properties because they are made under different conditions.

The properties of a polymer depends on:

A thermosoftening polymer consists of individual, tangled chains with no cross-links between them.

True. Thermosoftening polymers can be melted and remoulded to form different shapes.

Two components of a composite are:

False. In a composite, the reinforcement is surrounded by a matrix.

The reinforcement and matrix used to make concrete are: 0

True. The matrix in carbon fibres is a polymer.

True. Wood is a natural composite.

Examples of composites include:

Soda-lime glass is made by heating a mixture of sand, sodium carbonate and limestone.

False. Borosilicate glass has a higher melting point than soda-lime glass.

Clay ceramics are made by shaping / moulding wet clay and then heating them in a furnace.