10.9 Ceramics, polymers and composites
5 exam questions worth 9 marks. Write your answer, open the mark scheme, then give yourself the marks you earned. Your answers are saved on this device.
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What are the raw materials for soda-lime glass?
Choose one answer.
Correct Not quite: the answer is Sand, sodium carbonate and limestone
Mark scheme
A
Model answer
A: sand, sodium carbonate and limestone are heated together.
Explain why thermosetting polymers do not melt when heated, but thermosoftening polymers do.
Mark scheme
- thermosetting polymers have cross-links between chains (1)
- thermosoftening polymers have separate chains with only weak forces between them (1)
- the weak forces are overcome on heating so the chains can move; cross-links are strong bonds that do not break (1)
Model answer
In thermosoftening polymers the chains are separate, with only weak intermolecular forces, so they can move apart when heated. In thermosetting polymers, strong cross-links hold the chains together, so they do not melt.
Describe the difference in how low density and high density poly(ethene) are made.
Mark scheme
- LDPE: high pressure, trace of oxygen (1)
- HDPE: lower temperature and pressure with a catalyst (1)
Model answer
LDPE is made at high pressure with a trace of oxygen; HDPE is made at a lower temperature and pressure using a catalyst.
What is a composite? Give one example.
Mark scheme
- reinforcement (fibres / fragments) in a matrix / binder (1)
- e.g. fibreglass, carbon fibre, concrete, wood (1)
Model answer
A material made of a reinforcement, such as fibres, held in a matrix or binder; for example, fibreglass.
Explain why borosilicate glass is used for laboratory glassware instead of soda-lime glass.
Mark scheme
- it has a higher melting point / withstands high temperatures (1)
Model answer
Borosilicate glass melts at a higher temperature, so it can be heated strongly without melting or cracking.
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