Properties of Materials (OCR GCSE Chemistry A (Gateway))

Properties & Uses of Materials

Ceramics

• Ceramics are hard, non- metallic materials, such as brick, china, and glass 

• 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 include brick, china and porcelain.

• 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

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

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

• 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

Metals 

• Metals have many useful properties including:

  • good conductors of electricity 

  • malleable- can be hammered into shape 

  • ductile- drawn into wires 

• This makes them particularly useful for use in overhead electrical cables 

Choosing Materials

• The use of a material is dependent on its properties 

• For any given use, there may be more than one material that has the desired properties

• In cases like this, it is useful to evaluate the advantages and disadvantages of each material