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chemistry > 10 Using resources > Flashcards

10 Using resources Flashcards

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1
Q

what is a composite material

A
  • made of one material embedded in another
  • have a matrix which is the binder
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2
Q

examples of composite materials

A
  • fibreglass - consists of fibres of glass embeded in polymer, low density but very strong used for skis, boats and surfboards
  • carbon fibres - also have polymer matrix, reinforcment is from long chains of C atoms or from C nanotubes, very strong and light used in aerospace and sports car manafacturing
  • concrete made of aggregate embeded in cemenet, very strong ideal for building material
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3
Q

what is a thermo-setting polymers

A
  • contain monomers that can form cross-links between polymer chains holding them together in a solid structure
  • don’t soften when heated
  • strong hard and rigid
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4
Q

what are thermo-softening polymers

A
  • contain individual polymer chains entwined together with weak forces between the chains
  • can melt these plastics and remould them
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5
Q

difference between low density (LD) polymers and high density
(HD)

A
  • LD is made from etehene at moderate temperatures under high pressure and with a catalyst, flexible and used for bags and bottles
  • HD made from ethene but at a lower temperature and pressure with a different catalyst, more rigid, used for water tanks and drainpipes
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6
Q

properties of ceramics

A

glass and clay ceramics eg. porcelain and bricks
- insulators of heat and electricity
- brittle and stiff

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7
Q

properties of polymers

A
  • insulators of heat and elctricty
  • can be flexible and easily moulded - thermosoftening
  • used in clothing and as insulators in electrical items
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8
Q

porperties of composites

A
  • depend on the matrix/bider and the reinforcement used to make them
  • have many different uses
  • fibre glass, carbon fibre, concrete, wood
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9
Q

properties of metals

A
  • malleable
  • good conductors of heat and electricty
  • ductile can be drawn into wires
  • have many uses eg. electrical wires, car body-work and cutlery
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10
Q

how are alloys made

A
  • adding another element to the metal
  • disrupts the structure of the metal making alloys harder than pure metals
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11
Q

examples of alloys

A
  • bronze = copper + tin, used in medals, decorative ornaments and statues
  • brass = copper + zinc, used where lower friction needs eg. water taps, door fittings
  • gold alloys, zinc, silver and copper used to allow gold to be used in jewlerry pure gold too soft
  • aluminium alloys, used in aircrafts
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12
Q

what is the equation for the formation of rust

A

iron + oxygen + water —> hydrated iron(III) oxide

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13
Q

what is corrosion

A

where metals react with substance in their environment and are gradually destroyed

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14
Q

what happens when iron is exposed to oxygen and water

A
  • it rusts
  • flakes off the surface leaving more iron to rust and corrode
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15
Q

what happens when aluminium is exposed to air

A
  • forms aluminium oxide on the outer layer of the aluminium creating a protective layer
  • prevents any further corrosion taking place
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16
Q

what type of methods are there to prevent corrosion

A
  • barrier method
  • sacraficial method
  • some methods use both eg. an object can be galavanised by spraying a coat of zinc - firstly protective but if scratched zinc around the site of the scratch works as sacraficial metal
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17
Q

barrier methods for preventing corrosion

A
  • painting/coating with plastic
  • electroplating - uses electrolysis to reduce metal ions onto an iron electrode, can be used to coat iron with a layer of a different metal that won’t corrode
  • oiling/greasing - has to be used when moving parts involved eg. bike chains
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18
Q

sacrificial methods to prevent corrosion

A
  • involves placing a more reactiev metal such as zinc or magensium with the iron
  • water and oxygen react with the sacrifical metal instead of with the iron
  • used on boats
19
Q

what are natural resources

A
  • form without human input
  • includes anything made from earth, sea or air
  • some can be replaced with synthetic products or improved by man-made processes
  • Agricluture provides conditions where natural resources can be enchanced for our needs
20
Q

what are renewable resources

A
  • reform at a similiar rate or faster than we use them
  • eg, fresh water, food, timber
21
Q

what are non-renewabele sources

A
  • aren’t formed quickly enough to be considered replacable
  • finite
  • fossil fuels, nuclear fields, minerals and metals found in ores in the earth
  • afte rextracted many go under man-made process eg. fractional distilation
22
Q

what is sustainable development

A
  • approach to development that takes account of needs of present society while not damaging the lives of future generations
23
Q

how can we extract copper

b

A
  • bioleaching - bacteria used to convert copper compounds in the ore into soluble copper compunds, seperating out coper from the ore in the process
  • the lechate (solution produced by the process) contains copper ions which can be extracted though elecotrolysis or displacement
24
Q

how can we extract copper

p

A
  • involves growing plants in soil that contains copper
  • plants can’t use or get rid of the copper so it gradually builds up in the leaves
  • plants can be harvested, dried and burned in a furnace
  • the ash contains soluble copper compounds which copper can be extracted through electrolysis or displacemnt
25
Q

why is recycling metals important

A
  • use much less energy that needed to mine and extract new metal
  • conserves the finite amount of each metal in the earth
  • cuts down in amount of waste getting sent to landfill
26
Q

how can we recylce metals

A
  • melting them and casting them into shape of the new product
  • depending on what the metal will be used for, the amount of speration required from recyclable metals metals can change
27
Q

how to write a life cyle assessment

A
  • getting the raw material - damage on environment for extraction, how much it costs
  • manafacture and packaging - amount of enrgy used, any waste products and hwo to dispose of them
  • using the product - ho wlong it will last for, how many uses it gets, does use fo product damage the environment
  • product disposal - where will the be disposed - landfil?, energy used ot dispose them, products may get incincerated causing air pollution
28
Q

what are the problems with life cycle assesments

A
  • th use of energy, sme naturla resources and amount of certain types of waste produced by a porduct ovdf its lifetime can be easily quanitied by effcect of pollutants is harder
  • nto an objective mthod as it takes into accoutn the valies of the perosn carryign out the assessment - so LCA’s can be biased
  • Selectiev LCAs will show only some of the impacts of a porduct on the enviornemtn, cna be deliberatly writtein to suport claims of a company to hive them positive advertising
29
Q
A
30
Q

what is potabel water

A
  • water that’s beem treated or is naturally safe for humans to drink
  • not pure! pure water only has H2O molecules
  • has a pH between 6.5 and 8.5
31
Q

how is potable water produced

filtration

A
  • a wire mesh screens out large large twigs
  • gravel and sand beds filter out any other solid bits
  • sterilisation - water is sterilized to kill any bacteria and microbes
  • can be done by bubbling chlornr gas, usign ozone or shining UV light
32
Q

how is potabel water produced

disillation

A

used in dry areas where insteas there is sea water
- first test oH of water usning a pH meter, if too high or too low you need to neutralise it
- test the water for presence of sodium chloride using a flame test and halide test
- to distil the water pour the salty water into a distilation aparatus
- heat flash from below, water boils and forms steam leaving dissolved salts in flask
- steam condenses back to liquid water in condenser and can be collected as it runs out
- rtest the distilled water for sodium chloride and pH of water

33
Q

how else can potable water be produced

A
  • reverse osmosis
  • salty water passed through a membrane rhat only allows water molecu;es to pass through
  • ions and large molecules trapped by membrane so seperate from water
  • requires a lot of energy so very expensive
34
Q

how do we treat sewage

A
  1. Water is passed through a mesh screen
    to remove large bits e.g twigs or grit
  2. Chemicals are added to make solids and
    microbes stick together to form
    sediment and sink leaving a sludge on top
  3. Effluent is remobved an treated by biological aerobic digestion - air is pumped through the water to encourage aerobic bacteria to break down any organic matter
  4. Sewage is removed and transfered into large tanks where it gets broken down by bacteria in anaerbobic digestion
  5. During anaerobic digestion organic matter in the sludge is broken down releasing methane gas which can be used as an energy source and remaining waste can be used as fertiliser
  6. The water is then sterilised with chemicals eg. chlorine or UV radiation to kill any microbes left.
35
Q

what does the harber process produce

A

nitrogen + hydrogen <—> ammonia
N2+ 3H2 <—> 2NH3

36
Q

describe the harber process

A
  • nitgoen and hydrogen are passed over an iron catalyst
  • 450 degrees and 200 atmsopheres used
  • as ammonia cools down it condense and liquifies and is removes
  • since reversibel some ammonai will convert back to hydrogen and nitrogen
  • any gas that onverted back or didn’t react gets recycled
  • ammonia produced can be used to make ammonium nitrate - nitrgoegn rich fertiliser
37
Q

what compromises are made in the harber process

A
  • 450 degrees - forward reaction is ecothermic so if temp increased more reactant woudl be produced ratehr than ammonia however at low temperatures the reaction would be slower, 450 is a compromise between maximum yield and speed of reactio
  • 200 atmospheres - higher pressure means more forward reaction since 4 molecules on left for every 2 on the right, pressure set as high as possibel without makign it too expensive
38
Q

what are fertilisers

A
  • formulations which contain Nitrogen, phosphorus and pottasium which help plants to increase crop yield as crops can grow faster and bigger
39
Q

what are NPK fertilisers

A
  • formulations containign salts of nitrogen, phosphorus and pottasium in the right precentages
40
Q

ammonium nitrate symbol+word equation

A

NH3 +HNO3 —> NH4NO3
Nitrogen + Nitric acid —> Ammonium nitrate

41
Q

how is ammonium nitrate produced in industry

A
  • carreid out in giant vats at high concentrations rslultign in a very expthermic reaction
  • heat released evaporates water from the mixture - makes very concentrated ammonia nitrate
42
Q

how is ammonium nitrate produced in a lab

A
  • carried out on a small scale
  • through titration and crystilistaion
  • reactants are at a much lower concentration so less heat is produced by the reactoin and it’s safer for a person to carry out
  • after titration the mixture needs to be crstalised to give pure ammonium nitrate crystas
  • crystilisation isn’t used in inidstry because it’s very slow
43
Q
A

chemistry (11 decks)

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