Ceramics, Polymers, Composites & Metals (Edexcel GCSE Chemistry): Revision Note

Ceramics, Polymers, Composites & Metals

The physical properties of glass and clay ceramics, polymers, composites and metals are related to their uses:

Glass Ceramics

• Transparent and strong, glass insulates against heat

• 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

• Can be tailor designed to have specific properties for specific uses

• Can be made opaque or transparent

• Usually tough and flexible, some specialist polymers can be brittle

• Poor conductor of heat and electricity

Composites

• Made from two components: reinforcement and matrix

• The matrix is what binds the reinforcement together

• Common examples include fibreglass and steel reinforced concrete

• The properties of composites depend on the reinforcement and matrix used so composites can be tailor engineered to meet specific needs

Examples of Everyday Composite Materials

Metals

• Shiny, malleable and ductile so can be hammered into different shapes

• Can be mixed with other elements to form alloys, which have different properties to the elements they contain

• Corrosion resistant metals can be produced which last longer than other metals

• Good conductors of heat and electricity

Effective Use of Materials

Glass & Metals

• Glass and steel are extremely useful building materials

• Apart from its transparency, the hardness and the high compressive strength of glass makes it an ideal material for making walls and windows

• Metals are used extensively in electrical cabling and in electronics due to their ability to conduct electricity

• Copper is the most frequently used as it is a good conductor and is very malleable and easy to thread into cables

• Aluminium is a very strong metal but is also very light

• This makes it ideal for use in the construction of airplanes as it has a high strength-to-weight ratio

Glass and metals are exceptional building materials due to their high strength and durability

Composites

Reinforced concrete

• 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

Carbon-Fibre Composites

• Carbon fibres composites are extremely strong and low weight, hence they are used in aviation, aeronautics and for making professional racing bicycles

Carbon fibre composites have a very high strength to weigh ratio

Polymers

• As they are poor conductors of heat and electricity, this makes polymers good thermal and electrical insulators

• These properties are extremely useful for insulating electrical wiring as they prevent electric shocks and overheating

• The low melting points and flexibility of polymers enable them to be moulded easily into an infinite variety of shapes

The plastic coating on electrical wires makes use of the flexibility and insulating properties of polymers