Chemistry GCSE - C3 Material Choices - Revision Notes

My revision notes on GCSE Chemistry - OCR 21st Century Science - C3 Material Choices. Hope they help!

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  • Created on: 19-12-11 15:43
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C2 ­ Material Choices ­ Revision Notes
All materials are made up of chemicals. We use a variety of materials including metals, ceramics and
Mercury is a chemical element. It's made from mercury atoms. Hg
Water is a chemical. It's made of lots of water molecules. Molecules are groups of atoms bonded
together. Water molecules contain two chemical elements; hydrogen and oxygen. H H
Some materials are mixtures of chemicals ­ they contain different substances that
are not chemically bonded together.
Some materials occur naturally, for example Wood, Paper, Cotton, Silk, Wool and Leather.
Others are synthetic...
1. Rubber ­ Used to come from the sap of the rubber tree. We still get some rubber this way
but rubber can also be made in factories. Here it's properties can be controlled, so rubber
can be created for different purposes.
2. Lots of clothes are made from man-made fabrics like nylon. The properties of synthetic
fabrics can also be controlled. Eg. you can make fabrics that are waterproof, or stretchy.
3. Most paints are mixtures of synthetic chemicals. The pigment is made to be tough so that
the colour doesn't fade.
Raw materials used to make man-made materials come from the earth's crust.
Different materials have different properties:
Property Description Example
Melting Point Most chemicals made from The Melting point of Water is
pure materials have a melting 0°C
point, where a solid turns to a
Strength Strength is how good a material Ropes need a high tensile
is at resisting a force. Strength strength, otherwise they would
can be judged by the force snap.
needed to break or Bricks need a high compressive
permanently damage it. force, otherwise they would be
TENSILE STRENGTH is how squashed by the weight of
much a material can resist a other bricks above them.
pulling force. COMPRESSIVE Cross beams in roofs need to
STRENGTH is how much a be made from materials with
material can resist a pushing high compressive and tensile
force. strength because they get
pushed and pulled.
Stiffness Stiff Materials are not good at Steel is difficult to bend, its very
bending when a force is applied stiff.
to them. This is not the same as Rubber is strong, but some
strength. A flexible material can kinds can be very bendy.
be strong if a large force does

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Hardness Hardness is how difficult it is to The hardest natural material is
cut into a material. diamond, it can only be cut by
another diamond. Diamonds
can cut most materials ­ lots of
industrial drills have diamond
Density Density is a material's mass per Air is not very dense, to make
volume (eg g/cm3). Density is 1kg you'd need a large volume
not mass or weight. of it.
Gold is very dense, a small
volume would make 1kg.…read more

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Hydrocarbon properties change as the chain get longer, short chain molecules have lower boiling
points - they're often gases - and long chain hydrocarbons have higher boiling points, they can be
quite viscous (thick and sticky). It is down to the forces in between hydrocarbons.
There are two main bonds in crude oil:
The strong covalent bonds between the carbons and the hydrogens within each
hydrocarbon molecule.
The Intermolecular forces of attraction between different hydrocarbon molecules in the
mixture.…read more

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A small amount of hydrocarbons from crude oil are used to make new compounds for use in
things such as fertilisers, plastics, medicines, and food.
Some of the less useful hydrocarbons can also be split apart to make more useful
hydrocarbons and ethane, which is really useful for making plastics.
The process of making new compounds is called chemical synthesis.
Plastics are formed when lots of small molecules called monomers join together to make a very long
molecules called polymers, they're usually carbon based.…read more

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The stronger the bonds or forces between the polymer chains, the more energy is needed to break
them apart, and the higher the melting point.
Polymers can be chemically modified to change their properties:
1. Polymers can be modified to change their chain length, polymers with short chains are easy
to shape and have lower melting points, longer chain polymers are stiffer and have higher
melting points.
2.…read more


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