AQA GCSE Chemistry

Revision Notes

10.3.3 Ceramics, Polymers & Composites

Ceramics

Due to their high melting points and thermal resistance, ceramics are used widely as a construction material as well as domestic appliances

Glass Ceramics

  • Transparent and strong, glass insulates against heat and its transparency makes glass the ideal material for making windows
  • Glass ceramics are also more durable than other materials hence they are better suited for use in windows than plastic
  • Most of the glass produced is soda-lime glass which is made by heating a mixture of limestone, sand and sodium carbonate (soda) until it melts
  • On cooling it solidifies to form glass
  • A variation is borosilicate glass which is made using sand and boron trioxide and has a higher melting point than soda-lime glass

Clay Ceramics

  • These are hardened materials that resist compressive forces
  • Clay is a soft material dug up from the earth which hardens at high temperatures and when it is fired, produces a very strong and hard material
  • This allows bricks to be used to build walls which withstand the weight and pressure of the material bearing downwards on itself

Polymers

  • Polymers are poor conductors of heat and electricity, hence they are good thermal and electrical insulators
  • These properties are extremely useful for insulating electrical wiring as they prevent electric shocks and overheating

Electrical Wire Insulated, IGCSE & GCSE Chemistry revision notes

The polymer polyvinyl chloride (PVC) is commonly used to insulate electrical wiring

  • Depending on the manufacturing process used, the same polymer can have different properties
  • Polythene for example can be made at high pressure and moderate temperature to produce low density polythene (LDP) which is used for bags and bottles where flexibility is needed
  • If it is produced at lower temperatures and pressures and with the use of a catalyst, a much higher density (HDP) polythene is produced. This polymer has a more rigid, solid structure and is used to produce water tanks, mouldings, drain pipes etc
  • Polymers can also be divided into thermosoftening and thermosetting polymers
  • Thermosoftening polymers consist of individual chains entwined with each other with weak intermolecular forces holding the polymer chains together
  • These polymers therefore have low melting points, can be melted and remoulded to form different shapes
  • Thermosetting polymers on the other hand have strong cross-links between monomers on different polymer chains that hold the structure together
  • These are strong and rigid structures that don’t soften under heating

Exam Tip

Polymers are made from smaller units called monomers that link together to form a long polymer chain.

Composites

  • These are made from two components: reinforcement and matrix
  • The reinforcement material is embedded in the matrix material which acts as a binder
  • Common examples include fibreglass and steel reinforced concrete
  • Wood is an example of a natural composite as it consists of cellulose fibres held together by an organic polymer mix

Examples of Composite Materials, downloadable IGCSE & GCSE Chemistry revision notes

  • The properties of composites depend on the reinforcement and matrix used so composites can be tailor engineered to meet specific needs
  • Carbon fibres for example are extremely strong and low weight, hence they are used in aviation, aeronautics and for making professional racing bicycles
  • Steel reinforced concrete has immense tensile and compressive strength allowing it to be used as columns and supporting structures in construction

Diagram showing a concrete beam which is reinforced with steel, providing much more tensile strength

Exam Tip

Don’t get confused between an alloy and a composite: Alloys are uniform mixtures of metals whereas composites have two or more distinguishable materials.

Author: Francesca

Fran has taught A level Chemistry in the UK for over 10 years. As head of science, she used her passion for education to drive improvement for staff and students, supporting them to achieve their full potential. Fran has also co-written science textbooks and worked as an examiner for UK exam boards.
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