4.10.3 Using materials

What is corrosion?

The destruction of materials by chemical reaction with substances in the environment.

Give an example for a type of corrosion.

Rusting.

What is rusting?

The corrosion of iron when it is exposed to water and air, forming iron oxide.

How is corrosion different to iron?

Corrosion can happen in metals and non-metals, whilst rust is solely for iron. Corrosion corrodes the entire materials inside and out, whereas rust only appears on the exposed surfaces.

How can corrosion be prevented?

By applying a coating that acts as a barrier, e.g. grease, paint, electroplating.

How is aluminium protected from corrosion?

It has an oxide coating that protects the metal from further corrosion.

What is sacrificial protection?

When a more reactive metal is present in a coating, so that the more reactive metal corrodes rather that the protected metal.

Give an example of sacrificial protection.

Zinc is used to galvanise iron.

What is an alloy?

A mixture of two or more metals that aren’t chemically bonded.

Why do we make alloys?

To borrow the beneficial properties from other metals and mix them together t make one really god metal alloy.

Why are metal alloys stronger than pure metals?

In a pure metal the atoms are all uniform and are arranged in neat rows and layers, this means that they can easily slide over each other which results in them being weak. However, alloys of different elements have atoms of different sizes, which distorts the regular layers as some are bigger and some are smaller. This makes the layers a lot more difficult to slide over each other so they are strong.

What is bronze an alloy of?

Copper and tin.

What is bronze used for?

medals

What is brass an alloy of?

Copper and zinc.

What is brass used for?

Musical instruments, kitchen taps/faucets.

In jewellery what is mixed with gold?

Silver, copper and zinc

What is the proportion of gold measured in?

carats. (100% = 24 carats)

What is steel an alloy of?

Iron and specific amounts of carbon.

How the amount of carbon is steel affect the metals properties?

High carbon steel is strong but brittle.

Low carbon steel is softer and more malleable.

What is stainless steel, and what makes it “stainless”?

Stainless steel means that it is resistant to corrosion. If chromium and nickel are put in the alloy they become hard and resistant to corrosion.

What is cast iron an alloy of?

Iron, carbon phosphorus, silicon and sulfur.

Why and how do we convert cast iron into steel?

By removing impurities and adding chromium, manganese or nickel. This is because cast iron is very brittle and not very useful.

Are aluminium ally low or high density?

Low.

How is soda-lime glass made?

By heating sand, sodium carbonate and limestone.

How is borosilicate glass made?

By heating sand and boron trioxide.

Name a difference between soda-lime and borosilicate glass.

Borosilicate has a higher melting point.

What are some uses for glass ceramics and their properties?

They are strong and good heat insulators. They can be used for transport and windows.

How are clay ceramics made?

Soft clay material is dug up from the earth, It is removed of its impurities and them shaped and heated.

What are some uses for clay ceramics and their properties?

They are very strong and hard once heated, and they resist compressive forces. They can be used for pottery and bricks.

What is a polymer?

A long chain of monomers.

What are some uses for polymers and their properties?

They can be used to cover wires to prevent electric shocks or overheating. Because they are poor conductors of heat and electricity.

What is low density polyethene and how is it made?

Made at high pressures and moderateure temperatures, they are more flexible and therefore used in bags and bottles.

What is high density polyethene and how is it made?

Made at low pressures and low temperatures, more rigid and solid therefore used in drain pipes.

What are thermosoftening polymers and their properties?

Low melting points, when heated they become softer and more malleable. This is because of the weak intermolecular forces holding the polymer chains together.

What are thermosetting polymers and their properties?

They have higher melting point and are stronger and more rigid. When heated they become more or stay rigid and don’t soften. This is because of their strong cross-links between monomers on different polymer chains that hold the structure together.

What is a composite made of?

A matrix and a reinforcement.

How to composite materials work (their structure)?

The reinforcement material is embedded in the matrix material and acts as a binder.

Give some examples of composites and their two components.

• composite = reinforcement + matrix

• concrete = steel + concrete

• fibreglass = glass fibres + polymer resin

• carbon fibre/tubes = carbon fibres/nanotubes + polymer resin