SC26 Flashcards
SC26a
1) Recall what ceramics are, and their properties
2) Explain what glass is and its properties
3) Explain what clay ceramics are
1) Ceramics are a range of durable compounds that change very little when heated. They are chemically unreactive, hard and stiff but brittle. They are also poor electrical and thermal conductors, and have high melting points.
2) Glass is made by melting sand, then allowing it to cool and solidify.
Properties include:
- 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
3) Clay ceramics are made from clay moulded into shape. When the clay is heated to a very high temperature, tiny crystals form and join together.
- 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
SC26a
1) State some properties of metals
2) State some properties of polymers
1) - 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
2) - 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
SC26b
1) Recall what composite materials are.
2) Give some examples of composite materials.
1) A composite material is a mixture of two or more materials, combined to produce a material with improved properties. The individual materials often have contrasting properties.
2) Composite materials include:
- Fibreglass, which is reinforced with glass fibres, and the matrix is polymer resin.
- Concrete, which is reinforced with steel, and the matrix is concrete.
- Carbon fibre, which is reinforced with carbon fibres, and the matrix is polymer.
SC26c
1) Recall what nanoparticles are.
2) What is the size of nanoparticles?
3) Calculate the surface area to volume ratio of a nanoparticle.
1) Nanoparticles are tiny particles which are between 1-100nm in size.
2) Nano particles are 1-100nm in size. Atoms have a radius of about 0.1 nm (nanometres).
3) To calculate the surface area to volume ratio of a nanoparticle, you divide the surface area by the volume.
SC26c
1) Relate the uses of nanoparticulate materials to their properties.
2) Explain some possible risks associated with nanoparticles.
1) The surface area to volume reaction of nano particles is much higher than of larger particles. This gives nanoparticles different qualities because a much greater proportion of their atoms are available to interact with other substances.
2) - The risks are not fully known because they are a new technology.
- They might enter the body and catalyses reactions in the body.
1) What type of structure does ceramic materials have?
2) Explain how glass is made
1) Ceramic materials consist of giant structures with many strong bonds (covalent or ionic), giving them their typical properties.
2) 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.
Why are nanoparticles of titanium(IV) oxide used in some sunscreens?
It can absorb and block UV light from the skin, which can prevent sunburn.
Also, particles are very small, and therefore cannot be seen, on the skin.
