using resources excl water Flashcards
clay ceramics:
1) how made
2) 2 examples
+ what are ceramics
ceramics are non metal solids, high melt points no carbon
1) made by digging up soft, wet clay. this is easily moulded. fired in a furnace at high temperatures, hardens to form clay ceramic.
2) POTTERY AND BRICKS
glass (ceramic):
2 types
how each made
common?
difference
use
soda-lime glass; heating limestone, sand, and sodium carbonate until it melts. cools and forms glass. glassware- cups
borosilicate glass: heat a mixture of sand and boron trioxide until it melts. cools and forms glass. less common. higher melting point. test tubes
general physical properties of ceramics
glass AND clay:
1) insulators of heat and electricity
2) brittle (hard but not flexible and break easily)
3) stiff
composites:
how made
what are they
what do properties depend on
1) made when fibres or fragments of a material (reinforcement) are surrounded by a material known as a matrix acting as a binder. one material embedded
2) materials made up of two materials
3) Their properties depend on the properties of the reinforcement and matrix/binder. properties vary
4 examples of composite, reinforcement & matrix, properties, use
- Fibreglass- composed of fibres of glass embedded in a polymer matrix. low density (plastic), strong (glass) . surfboards
- carbon fibre- reinforcement is long carbon chains bonded together or carbon nanotubes embedded in a polymer matrix. strong and light so used in racing cars. high strength to weight to ratio
- concrete- reinforcement of an aggregate (sand or gravel usually) and matrix is cement. strong so used in building material. skate parks
- wood- natural composite of cellulose fibres as reinforcement surrounded by an organic polymer matrix
what do the properties of the polymer depend on + general properties
properties depend on the monomer that they are made from and how they are made.
generally: insulators of heat and electricity, can be flexible and easily moulded
many applications
how are low density poly(ethene) LDPE and high density poly(ethene) made.
arrangement of both and melting point
LDPE made from ethene monomers at high pressures, moderate temp and low availability of o2. bags
HDPE from ethene monomers at a lower temperature and pressure + catalyst. hard hats, crates
both thermosoftening
LDPE is flexible, polymer chains are separated therefore intermolecular forces are low so less energy to overcome these, low melting point.
HDPE is rigid as polymer chains are tangled closely together. greater intermolecular forces so more energy to overcome which means it has a higher melting point
thermosetting vs thermosoftening polymers
thermosetting: monomers that form cross links between individual polymer chains, holding the polymer in a solid structure. don’t soften and don’t melt when heated, burn. held together by strong covalent bonds (cross links)
thermosoftening: individual polymer chains entwined with other chains, weak intermolecular forces between chains. no cross links just tangled chains. when heated, soften and melt and remould.
alloys: explain what happens
mixture of 2 or more metals, one of which is a pure metal
different size metal atoms disrupt metallic lattice, harder for layers to slide over.
harder
most metals in everyday use are alloys
3 types of steel: name, properties, uses
iron + carbon
low carbon steel (0.1-0.3%)- easily shaped- car bodies
high carbon steel (0.2-2.5%)- hard, strong, brittle- blades in cutting tools
stainless steel (chromium and nickel added)- corrosion resistant and cutlery, containers
alloys:
bronze
brass
gold alloys + carat system
aluminium alloys
metals used, uses
bronze- copper and tin; hard- medals, ornaments and statues
brass- copper and zinc. malleable, taps, instruments
gold alloys- gold + (copper,zinc,silver) hardens. jewellery. 24 carat pure gold. find out % of gold by carat no/24 * 100. 18 carat is 75% gold 18/24 *100.
aluminium alloys- alloyed to harden. aircraft manufacture. aluminium low density which is good for aircraft
corrosion:
1) what is it
2) what is rusting and what is needed
3) equation
1) destruction of metals/materials through chemical reactions with their environment. surface of material that is exposed
2) rusting is an example of corrosion. iron only. need air and water.
3) iron + oxygen + water -> hydrated iron oxide
rusting in iron vs corrosion in aluminium
when iron rusts, pieces of iron on surface flake away and more iron exposed. all iron eventually corrodes away
aluminium corrodes to form an oxide layer over it. this acts as a protective layer and stops any further corrosion so aluminium remains intact.
experiment for rusting + mass change of rusty nail
put an iron nail in a boiling tube. in one boiling tube put boiled water (remove o2) and oil (prevents oxygen coming in), in another test tube add calcium chloride (which will absorb any water from air) and in the final one add water and air.
leave for a week
one with water and air will rust, other 2 will not. mass of rusty nail will increase
what is barrier method and 3 ways- corrosion
prevents rusting as iron is coated to keep out h20 and o2.
painting/plastic coat.
electroplating- use electrolysis to reduce metal ions of a different metal that wont be corroded which coats iron.
oiling/greasing- reduce friction on moving parts.
