AQA GCSE Chemistry Foundation (8462), Foundation tier · Using resources › Using materials
Practise Ceramics, polymers and composites. 7 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
How glass and clay ceramics are made, why the conditions used to make poly(ethene) change its properties, how thermosoftening and thermosetting polymers differ in structure, and what composites are. This is in GCSE Chemistry only, not in Combined Science. Expect recall, structure-based explanations and questions where you compare data to select a material on Paper 2.
Borosilicate glass: sand + boron trioxide; higher melting point
Clay ceramics (pottery, bricks): shape wet clay → heat in a furnace
LD poly(ethene): very high pressure, trace of oxygen → branched chains, low density
HD poly(ethene): lower temperature and pressure, catalyst → mostly unbranched chains, high density
Thermosoftening: no cross-links, weak intermolecular forces → melts when heated
Thermosetting: covalent cross-links between chains → does not melt when heated
Composite = matrix (binder) + reinforcement (fibres or fragments)
Notes
Glass and clay ceramics
Most glass is soda-lime glass, made by heating a mixture of sand, sodium carbonate and limestone.
Borosilicate glass is made from sand and boron trioxide. It melts at a higher temperature than soda-lime glass, so it is used for ovenware and laboratory glassware.
Clay ceramics, including pottery and bricks, are made by shaping wet clay and then heating it in a furnace.
Glass and clay ceramics are hard but brittle, and are good insulators.
LD and HD poly(ethene)
diagram
The properties of a polymer depend on which monomers it is made from and the conditions under which it is made.
Low density (LD) poly(ethene) is made from ethene at a very high pressure, with a trace of oxygen. Its chains are highly branched, so they cannot pack closely: lower density, softer and more flexible (e.g. carrier bags, cling film).
High density (HD) poly(ethene) is made from ethene at a lower temperature and pressure, using a catalyst. Its chains are mostly unbranched, so they pack closely: higher density, stronger, more rigid, and softens at a higher temperature (e.g. milk bottles, pipes).
Branches keep LD chains apart, so LD poly(ethene) is less dense and softer.
Thermosoftening and thermosetting polymers
diagram
Thermosoftening polymers are separate polymer chains held together by weak intermolecular forces. On heating these forces are overcome, the chains slide past each other and the polymer melts, so it can be remoulded. Example: poly(ethene).
Thermosetting polymers have strong covalent cross-links between the chains. The cross-links hold the chains in place, so the polymer does not melt when heated (it chars at very high temperatures). Example: melamine.
Strong covalent cross-links hold thermosetting chains in place.
Composites
diagram
Most composites are made of two materials: a matrix (or binder) surrounds and binds together fibres or fragments of the other material, the reinforcement.
The composite combines the strength of the fibres with the properties of the matrix.
Examples: reinforced concrete (steel rods in concrete); fibreglass (glass fibres in a polymer resin); carbon fibre composites (carbon fibres in a polymer resin); wood (cellulose fibres in a natural matrix called lignin).
A composite combines the useful properties of its parts: concrete is strong when squashed but weak when stretched, and the steel rods make reinforced concrete strong when stretched too.
Don’t lose marks
Saying thermosetting polymers have 'strong intermolecular forces'. They have covalent cross-links between the chains.
Saying covalent bonds break when a thermosoftening polymer melts. Only the weak intermolecular forces between chains are overcome.
Saying LD and HD poly(ethene) are made from different monomers. Both are made from ethene; the conditions and catalyst differ.
Mixing up the matrix and the reinforcement: the matrix surrounds and binds; the reinforcement is the fibres or fragments.
Choosing a material from data without saying why the others are unsuitable.
LD = lots of branches, loosely packed; HD = hardly any branches, densely packed.
Thermo-SETTING: once set, it stays set (cross-links). Thermo-SOFTENING: softens every time it is heated.
In a composite, the reinforcement gives strength and the matrix is the glue that holds it together.
Exam technique
Structure-based 'explain' questions need a chain of three links: structure → forces or bonds → property.
In data questions, quote numbers with units and compare them, e.g. ‘density 1.5 g/cm3, lower than glass at 2.5 g/cm3’.
Learn at least one composite with its matrix and reinforcement named: reinforced concrete and fibreglass are the safest.
What each grade needs
What you need to be able to do, from the first marks up to the top grade.
Grade 3
Name the raw materials for soda-lime glassSand, sodium carbonate and limestone, heated together.
Grade 4
Describe how clay ceramics are madeWet clay is shaped and then heated in a furnace, e.g. to make pottery and bricks.
Grade 4
Name the two parts of a compositeA matrix (binder) surrounds and binds together fibres or fragments of the reinforcement.
Grade 5
Give examples of composites and their partsReinforced concrete is steel rods in concrete; fibreglass is glass fibres in a polymer resin.
Quick recall
Cover the answers and test yourself. The app has these as flashcards that come back just before you'd forget them.
Soda-lime glass is made by heating a mixture of sand, sodium carbonate and one other substance. Name the other substance.
limestone
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
(a) Soda-lime glass is made by heating a mixture of sand, sodium carbonate and one other substance. Name the other substance.[1]
(b) Describe how clay ceramics are made.[2]
(c) Give one example of a clay ceramic.[1]
Show the answer and mark scheme
(a)Answer: limestone
limestone / calcium carbonate
(b)
wet clay is shaped
and then heated in a furnace
(c)
pottery / bricks / tiles
Question 2Medium6 marks
Polymers can be thermosoftening or thermosetting.
(a) Explain the difference between thermosoftening polymers and thermosetting polymers. Refer to their structures and what happens when they are heated.[4]
(b) Which type of polymer should be used to make a saucepan handle? Give a reason for your answer.[2]
Show the answer and mark scheme
(a)
thermosoftening polymers are made of individual polymer chains (with weak intermolecular forces between them)
when heated the chains can slide over each other, so the polymer softens / melts
thermosetting polymers have cross-links (covalent bonds) between the chains