10.3 Using materials (Triple) Flashcards
Describe the compounds and the uses of bronze
Bronze is an alloy of copper and tin, used for making statues and decorative objects.
Describe the compounds and the uses of brass
Brass is an alloy of copper and zinc used for producing water taps and door fittings.
Describe the compounds and the uses of gold
Gold used as jewellery is usually an alloy with silver, copper and zinc (The proportion of gold in the alloy is
measured in carats, with pure gold being 24 carat, e.g. 18 carat gold is 75% gold.)
Describe the compounds and the uses of aluminium-magnesium alloys
Aluminium-magnesium alloys are low density and used in aerospace manufacturing.
Describe the compounds and the uses of steels
Steels are alloys of iron that contain specific amounts of carbon and other metals. High carbon steel is strong but brittle. Low carbon steel is softer and more easily shaped.
Steels containing chromium and
nickel (stainless steels) are hard and resistant to corrosion.
What is corrosion and how is it prevented?
Corrosion is the destruction of materials by chemical reactions with substances in
the environment, e.g. rusting.
Corrosion can be prevented by applying a coating that acts as a barrier, such as
greasing, painting or electroplating. These methods stop the air or water coming
into contact with the metal.
Describe sacrificial
protection
Some coatings are reactive and may contain corrosion inhibitors or a more
reactive metal.
If two metals are in contact the more reactive metal will corrode instead of the less reactive one, e.g. zinc is used to galvanise iron and when scratched, provides
sacrificial protection because zinc is more reactive than iron.
How are the properties of
polymers determined?
The properties of polymers depend on what monomers they are made from and the conditions under which they are made.
For example, low density (LD) and high density (HD) poly(ethene) are produced from ethene, using different catalysts and reaction conditions.
Describe the structure of
thermosoftening polymers
Thermosoftening polymers soften easily on
heating and can then be remoulded, keeping the new shape on cooling. The polymer molecules are attracted to each other by weak intermolecular forces.
Describe the structure of
thermosetting polymers
Thermosetting polymers do not melt on heating. The polymer molecules are linked to each other by strong cross-links.
How is glass made?
Most of the glass we use is soda-lime glass, made by heating a mixture of sand, sodium carbonate and limestone.
Borosilicate glass, made from sand and boron trioxide, melts at higher temperatures than soda-lime glass.
How are clay ceramics made?
Clay ceramics, including pottery and bricks, are made by shaping wet clay and then heating in a furnace.
How are composites formed?
Fibres or fragments of one material (reinforcement) are surrounded by a
binder/matrix material that holds these fibres/fragments together.
E.g. fibreglass - glass fibres bound together in a polymer, used for making storage
tanks.
