Material Choices

"How is data used to choose a material for a particular use?"

"By comparing physical properties such as melting/softening point, conductivity, strength, stiffness, flexibility, brittleness, hardness, density, and ease of reshaping"

"What are the properties and uses of glass ceramics?"

"Transparent, hard, brittle, poor heat and electrical conductors; used for windows, bottles"

"What are the properties and uses of clay ceramics?"

"Opaque, hard, brittle, poor heat and electrical conductors; used for bricks, porcelain"

"What are the properties and uses of polymers?"

"Can be transparent/translucent/opaque, poor heat and electrical conductors, can be tough or ductile; used for plastic bags, bottles"

"What are the properties and uses of metals?"

"Shiny, good heat and electrical conductors, hard, tough; used for cars, bridges, electrical cables"

"Why are most metals used as alloys?"

"Pure metals are too soft; mixing with other metals disrupts structure, making alloys harder and stronger"

"Why are pure copper

gold, iron and aluminium not used directly?","They are too soft; mixing with small amounts of other metals makes them harder"

"How does alloying make metals harder?"

"Different-sized metal ions disrupt the regular structure, preventing layers from sliding easily"

"What are steels?"

"Alloys of iron and carbon (sometimes with other metals) designed for specific uses"

"What are the properties and uses of low-carbon steel?"

"Easily shaped (malleable); used for sheeting"

"What are the properties and uses of high-carbon steel?"

"Hard; used for cutting tools"

"What are the properties and uses of stainless steel?"

"Contains chromium and nickel, resistant to corrosion; used for cutlery"

"What are the properties and uses of aluminium alloys?"

"Low density; used for aircraft"

"What are the properties and uses of copper alloys?"

"Good electrical conductor; used in electrical cables"

"What are the properties and uses of gold alloys?"

"Resistant to corrosion; used in jewellery"

"What are the properties and uses of magnalium (Al + Mg)?"

"Low density; used in cars and planes"

"What are the properties and uses of brass (Cu + Zn)?"

"Hard, resistant to corrosion; used in coins"

"What is addition polymerisation?"

"Joining alkene monomers by breaking C=C bonds to form long-chain polymers"

"What is the repeat unit in an addition polymer?"

"The monomer without the C=C bond, repeated with brackets and an 'n'"

"How do you deduce the monomer from an addition polymer?"

"Identify the repeating unit, then add back the C=C bond"

"What is condensation polymerisation?"

"Reaction of two different functional groups to form a polymer and a small molecule (e.g. water)"

"What functional groups form condensation polymers?"

"Alcohol + carboxylic acid → polyester; Amine + carboxylic acid → polyamide; Amino acids → proteins"

"What must a monomer contain to undergo condensation polymerisation?"

"At least 2 functional groups"

"What is DNA made of?"

"A polymer of four different nucleotides arranged in a double helix"

"What other natural polymers are important for life?"

"Proteins (amino acids), starch (glucose), cellulose (glucose)"

"How do covalent bonds affect material properties?"

"Strong bonds; macromolecules have high melting points; simple molecules have low melting points due to weak intermolecular forces; do not conduct (except graphite)"

"How do ionic bonds affect material properties?"

"Strong bonds; high melting points; conduct when molten/aqueous but not solid"

"How do metallic bonds affect material properties?"

"Strong bonds; high melting points; conduct electricity; flexible; hard; layers allow reshaping"

"Why don't individual atoms have bulk properties?"

"Properties depend on bonding, intermolecular forces, and structure, not single atoms"

"What are the bonding and properties of polymers?"

"Covalent bonds in chains, strong intermolecular forces, solids at room temp, large molecules with high melting points, properties vary (e.g. poly(ethene) flexible, poly(propene) shatterproof)"

"What are giant covalent structures?"

"Large 3D structures with covalent bonds between all atoms, very high melting points"

"What are the structure and properties of diamond?"

"Each carbon bonded to 4 others; very hard, very high melting point, does not conduct electricity"

"What are the structure and properties of graphite?"

"Each carbon bonded to 3 others in layers; weak forces between layers so soft/slippery; one delocalised electron per atom so conducts electricity"

"What are fullerenes?"

"Molecules of carbon atoms in hollow shapes (spheres, tubes); useful in nanotechnology and electronics"

"What are carbon nanotubes?"

"Cylindrical fullerenes with very high length-to-diameter ratio; strong and conductive"

"What is graphene?"

"Single layer of graphite; very thin, strong, conducts electricity; used in electronics and composites"

"What size range are nanoparticles?"

"1-100 nm, containing a few hundred atoms"

"How does surface area:volume ratio change with particle size?"

"Smaller particles have larger surface area:volume ratios"

"Why are nanoparticles useful?"

"High surface area makes them good catalysts, sensors, in cosmetics, lubricants, electronics"

"What are some uses of nanoparticles?"

"Catalysts, selective sensors, stronger building materials, sun cream, deodorant, lubricants for joints/gears, small electrical circuits"

"What are possible risks of nanoparticles?"

"May enter bloodstream/brain due to small size, unknown health effects; more data on uses than risks"

"What are examples of nanoparticle benefits vs risks?"

"Benefits: stronger materials, medical uses; Risks: unknown long-term health effects"

"What is corrosion?"

"Destruction of materials by reactions with environment (e.g. rusting of iron)"

"What conditions are needed for rusting?"

"Both air (oxygen) and water present"

"How can rusting be prevented?"

"Excluding oxygen/water (paint, plastic coating, oil/grease, desiccant, vacuum) or sacrificial protection (galvanising with zinc)"

"What is sacrificial protection?"

"Protecting a metal by coating it with a more reactive metal that corrodes first (e.g. zinc galvanises iron)"

"What is oxidation in terms of oxygen?"

"Gain of oxygen"

"What is reduction in terms of oxygen?"

"Loss of oxygen"

"What are the main stages of a life-cycle assessment (LCA)?"

"Extracting/processing raw materials, manufacturing/packaging, use/operation, disposal (including transport at each stage)"

"Why are LCAs not purely objective?"

"Allocating numerical values to pollutants requires value judgments; selective LCAs can be misleading"

"What is PET recycling and why is it viable?"

"PET bottles can be melted, moulded, reused; saves crude oil, reduces environmental impact, cost-effective"

"What are the advantages of recycling materials?"

"Reduces energy use, saves raw materials, less quarrying/mining, less pollution, sustainable"

"What are the disadvantages of recycling materials?"

"Collection/transport costs, need to sort materials, different energy savings depending on material"