Properties of Materials (OCR Gateway GCSE Chemistry)

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 

• 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 

Answer:

• • In an evaluate question you need to consider the pros and cons of each material
  • Copper is the best electrical conductor but has the highest density so will be too heavy 
  • Steel has the highest tensile strength but the lowest electrical conductivity  
  • Aluminium has a higher tensile strength than copper, is a better conductor than steel whilst also having a lower density 
  • Aluminium is the preferred choice for overhead wires