C6.1 Flashcards
(164 cards)
1
Q
What are the three essential elements required for plants to grow?
A
- nitrogen, N
- phosphorus, P
- potassium, K
- absorb these nutrients from the soil
2
Q
What is the mineral diffidence symptom in plants when they don’t get enough nitrogen?
A
- Poor growth and yellow leaves
3
Q
What is the mineral diffidence symptom in plants when they don’t get enough Phosphorus ?
A
- discoloured leaves and poor root growth
4
Q
What is the mineral diffidence symptom in plants when they don’t get enough potassium?
A
- poor root growth and discoloured leaves
5
Q
What is the role of fertilisers?
A
- Fertilise replace elements in the soil used up by plants or provide more of them which helps the crop yield increase as the cops go faster and bigger
- must be water soluble so they can be absorbed through plant roots
6
Q
How is nitrogen, potassium and phosphorus absorbed by plants?
A
- nitrogen = nitrate ions = NO3^- or ammonia ions= NH4^+
- potassium = K+ ions
- phosphate = PO4^3-
7
Q
What are NPK fertilisers?
A
- most common fertiliser as they provide all 3 essential elements to plants in differing ratios depending on the one selected
8
Q
Why is ammonia used in fertilisers?
A
- it’s a base that can be neutralised by acids to make ammonium salts
- ammonia is important to world food production as it’s a key ingredient in many fertilisers
9
Q
What are the range of compounds made for use in fertilisers?
A
- ammonia nitrate = NH4NO3
- ammonia sulfate = (NH4)2SO4
- ammonia phosphate = (NH4)3PO4
- potassium nitrate = KNO3
10
Q
How is ammonium nitrate made?
A
- neutralise nitric acid with ammonia
- good fertiliser as it has high percentage of nitrogen, the ammonia and nitric acid
11
Q
How is ammonium sulfate made?
A
- neutralise sulfuric acid with ammonia = formed by Haber Process
12
Q
How is ammonium phosphate made?
A
- neutralising phosphoric acid with ammonia
13
Q
How is potassium nitrate made?
A
- neutralise nitric acid with potassium hydroxide
14
Q
How does a fertiliser factory make fertilisers?
A
- the industrial production of fertilisers are several integrated processes using a variety of raw materials
- e.g may make ammonia using Haber process, phosphorus acid from phosphorus rock, sulfuric acid using contact process or nitric acid
15
Q
What does the Haber process make and what is its symbol equation?
A
- makes ammonia from nitrogen and hydrogen
- reversible reaction = N2(g) + 3H2(g) ⇌ 2NH3(g) (reached equilibrium)
16
Q
What are the raw materials in the Haber process and how is nitrogen and hydrogen made in it?
A
- raw materials = air, natural gas and steam
- nitrogen is made from the fractional distillation of liquified air (air is 78% nitrogen)
- hydrogen is made by reacting natural gas with steam (can also be obtained from hydrocarbons from natural gas/crude oil)
17
Q
What reaction is used to make fertilisers?
A
- acid + alkali —> salt + water
- potassium hydroxide + sulfuric acid —> potassium sulfate + water
18
Q
What method could be used to make fertilisers?
A
- titration
- fill burette with acid, use a volumetric pipettes today add 25 cm cubed of alkali to the clinical flask
- add a few drops of indicator and record the start volume
- add acid while swirling the flask until the indicator changes colour
- record end volume and repeat until concordant rites (0.1cm cubed)
- after titration = add activated charcoal in solution = attracts the phenolphthalein and filter solution = evaporate solution = leaves the fertiliser crystals
19
Q
What colour is litmus in an alkali and acidic solution?
A
- alkali = blue
- acidic = red
20
Q
What colour is phenolphthalein in an alkali and acidic solution?
A
- alkali = pink
- acidic = colourless
21
Q
What colour is methyl orange in a alkaline and acidic solution?
A
- alkali = yellow
- acidic = red
22
Q
How can you make potassium sulfate in the lab?
A
- put dilute potassium hydroxide, KOH (aq) into a conical flask and add few drops of phenolphthalein (tells you when alkali is neutralised)
- add dilute sulfuric acid, H2SO4 (aq) from a burette and when changes from pink to colourless = stop
- add activated charcoal and filter mixture to remove it
- warm filtrate to evaporate the water, leaving potassium sulfate behind - don’t heat to dryness
23
Q
How can you make ammonia sulfate in the lab?
A
- add few drops of methyl orange to ammonia = turns yellow
- slowly add sulfuric acid from burette to solution until colour just changes from yellow to red ( means all ammonia is neutralised)
- gently swirl flask as you add acid
- ammonium sulfate now isn’t pure = has methyl orange in it = note exactly how much sulfuric acid it took to neutralise and repeat with no indicator
- gently evaporate solution using steam bath until only some left, leave to crystallise then filter out crystals and leave them to dry
24
Q
Why can’t you use titration in the industry?
A
- impractical as to use burette sand steam baths for large quantities and crystallisation is slow
- lab = start with pure substance but factory = raw materials (need to be purified)
25
What process do you need for large and small amounts of fertilisers in the industry?
- bulk chemical = continuous process
| - small quantities (pharmaceuticals) = batch process
26
What is important to consider in industrial processes?
Need to be economical through:
- rate of production
- relatively cost of equipment and energy
- numbers of workers needed
- shut-down period
- easy of automating the process
- cost and availability of raw materials
- equilibrium position
27
What features does a batch process have?
- low rate of production
- low relative cost of equipment
- large numbers of workers needed
- frequent shut down periods
- low easy of automating the process
28
What features does a continuous process have?
- high rate of production
- high relative cost of equipment
- small numbers of workers needed
- rare shut down periods
- high ease of automating the process
29
How does the cost and availability of raw materials effect industrial processes?
- raw materials need to refined/ purified or make them as part of chemical reaction = cost to extract, refine and make materials = cost = too high to source = might not be profitable
- some are non renewable = best to try use common/renewable materials
30
How does energy cost effect industrial processes?
- reaching/ maintaining the conditions required for reactions to happen = temp and Pa
- high temp and Pa = cost more to maintain = so low temp and Pa used wherever possible
31
How does the rate of reaction effect industrial processes?
- reasonable rate = sometimes might mean compromising yield
| - graph = shows rate change with reaction conditions = may keep increasing with temp or Pa or optimum conditions
32
How does the equilibrium position effect industrial processes?
- some reactions are reversible
- controlling position of equilibrium = maximises the amount of product made = makes industrial process more profitable (can control by cont. of reactants, pressure and temp)
- equil pos. = lies to the left = reaction = low yield (not much of reactant is made into products) and if difficult/ expensive to alter = reaction may not be viable
33
What are the conditions at which ammonia is made in the Haber Process?
- In industry =
- temp of 450 ° C
- pa of 200 atm
- in the presence of iron catalyst
34
How does pressure effect the Haber process?
- higher pressure favour forward reaction as 4 moles of gas on left for every 2 on right
- so pressure is set as high as possible for best yield without making it too expensive to build (plant that’d stand atm of 1000 = too expensive) so 200 atm
35
How does temperature effect the Haber process?
- forward reaction is exothermic = increasing temp = moves equilibrium position in the wrong way (away from ammonia and towards hydrogen and nitrogen) = yield is greater at low temp
- lower temp = lower rate of reaction so temp is increased to get a higher rate of reaction (compromise)
- 450 °C is a compromise between max yield and rate of reaction
36
What is the ammonia formed as in the initial stage?
- gas but cools in the condenser and liquifies and is removed
- unused hydrogen and nitrogen remain as has and the pumped back into reaction = recycled = nothing wasted= overall yield of 97%
37
How does the iron catalyst effect the Haber process?
- speeds up reactions and reduces cost
- makes reaction go faster which gets it to equilibrium proportions more quickly but it doesn’t effect the position of equilibrium (% yield)
- without catalyst = temp would have been raised even further for quick enough reaction which would reduces % yield = catalyst is important
38
What is the contact process used to make and what are the raw materials needed?
- sulfuric acid
| - raw materials needed = sulfur, air and water
39
What’s stage 1 of the contact process?
- sulfur and air as raw materials
- burn sulfur in air to make sulfur dioxide - SO₂
S + O2 → SO2
40
What’s stage two of the contact process?
- sulfur dioxide and oxygen react to produce sulfur trioxide which is a reversible reaction - SO3
2SO2 + O2 ⇌ SO3
41
What are the conditions to maximise the yield of the second step?
- 2 atmospheric pressure
- 450 °C temp
- vanadium oxide catalyst
= 96% yield
42
What’s the third stage of the contact process and what are its controlling hazards?
sulfur trioxide is converted into sulfuric acid by adding water to it
- SO3 (g) + H2O (l) → H2SO4 (aq)
- however stage 3 is a very exothermic reaction so if it was carried out as 1 step it would create an acidic mist
43
How do you actually carry out step 3?
- step 1= sulfur trioxide is passed through concentrate sulfuric acid to make oleum = H₂S₂O7
H₂SO4 (l) + SO3 —> H₂S₂O7
- step 2 = oleum is added to water to make a large volume of concentrated sulfuric acid
H₂S₂O7(l) +H₂O —> 2 H₂SO4
44
Where can conditions be changed in the contact process?
- step 2 as it’s reversible
| - there is compromise between the rate of reaction, yield and cost
45
How does temperature effect the Contact process?
- oxidiser sulfur dioxide to form sulfur trioxide (forward reaction) = exothermic
- high equilibrium yield is favoured at lower temperatures = equilibrium position shifts to right to replace the heat
- temp slow = slow reaction and vanadium oxide only works above 380°C so compromise of 450°C = acceptable yield quickly
46
How does pressure effect the Contact process?
- 2 moles of gas on products and 3 on reactants = forward
- higher yield = Pa should be increased so equilibrium position shifts to the right to reduce Pa
- but increasing pressure is expensive and equil is already on right
- so carried out just over atm at 2atm to just push gas through converter
47
How does the catalyst effect the Contact process?
- increases rate of reaction = vanadium pentoxide (V2O5)
| - doesn’t change the position of equilibrium
48
What are renewable materials?
Can be replaced as they are used so they don’t run out
49
What process is used for the production of the ethanol?
- ethanol is made from plant sugars using fermentation
- relies on a single cell fungi = yeast = has enzymes that catalyse the conversion of glucose solution into carbon dioxide and ethanol
- C6H12O6 → 2 C2H5OH + 2 CO2
- glucose —> carbon dioxide and water
50
How can you carry out fermentation?
- yeast cells become inactive if the temp = too low and enzymes become denatured above 50 degrees C so fermentation = at 35 degrees C under normal atm pressure
- glucose solution and yeast = placed in conical flask with bung on top
- delivery tube through bung to limewater which turns cloudy when CO2 produced
- industrial fermentation uses same condition with more complex equipment
51
What are non-renewable materials, give an example:
- non renewable = used up faster than replaced and will run out if you keep using them
- ethene is obtained from crude oil (non renewable material)
52
How is alcohol made from non renewable materials?
- ethanol can be produced by the hydration of ethene
- ethene + steam ⇌ ethanol
- C2H4 (g) + H2O (l) ⇌ C2H5OH (g)
53
Why can’t we produce ethanol from ethene in the lab?
- only suitable for industrial process as it needs a temp of 300 degrees C, Pa of 60 atm and a phosphoric acid catalyst
54
What is the cost of raw materials, conditions, energy requirements, rate of reaction, % yield, purity of product of the fermentation of sugars compared to the hydration of ethene?
- Cost of raw materials - low
- Conditions - moderate temp & norm Pa
- Energy requirements - low
- Rate of reaction - low
- % yield - low (~15%)
- Purity of product - low (needs filtering and fractional distillation)
55
What is the cost of raw materials, conditions, energy requirements, rate of reaction, % yield, purity of product of the hydration of ethene compared to the fermentation of sugars?
- Cost of raw materials -high
- Conditions - high temp & Pa
- Energy requirements- high
- Rate of reaction - high
- % yield - high (~95%)
- Purity of product - high (no by - products)
56
What factors does the process of making ethanol depend on?
- availability and cost of raw materials
| - cost of energy needed
57
What is an ore?
- rock mineral that contains enough metal to make it economical to extract (value of metal = more than cost of extracting it)
58
Give examples of ores and the meta compounds found within:
- malachite - copper carbonate
- bauxite - aluminium oxide (Al2O3)
- haematite - iron (III) oxide
59
What must happen to an ore to separate the metal compound?
- must be mined then processed to separate the metal compound rest of the ore
- pure metal is extracted from compound using chemical reactions
60
What does the method chosen to extract a metal depend on?
It’s position in the reactivity series
61
What are the methods of extraction?
- chemically by heating with carbon/ carbon monoxide or by electrolysis
- some ores have to be concentrated before extracting = get rid of rocky material
- displacement reactions or biological methods
62
What are the advantages and disadvantages of extracting using electrolysis and heating with carbon/ carbon monoxide?
- could be used to extract all metals regardless of position on reactivity series but expensive
- heating metal with carbon/carbon monoxide is cheaper than electrolysis but only works with metals less reactive than carbon
63
How is copper extracted from copper sulfide?
- Stage 1 = copper (II) sulfide is roasted in air:
- copper (II) sulfide + oxygen = copper (II) oxide + sulfur dioxide
- 2CuS(s) + 3O2 (g) —> 2CuO(s) + 2SO2 (g)
- Stage 2 = copper (II) oxide is heated with carbon
- copper (II) oxide + carbon —> copper + carbon dioxide
- 2CuO (s) + C (s) —> 2Cu (s) + CO2 (g)
64
What type of reaction is the extraction of copper from copper (II) sulfide?
- redox reaction as copper (II) oxide loses oxygen and is reduced and carbon gains oxygen and is oxidised
- carbon is the reducing agent as CuO is losing O2
- stage 2 is reduction (removal of oxygen)
65
What metals can be extracted by electrolysis and what metals can be extracted by heating with carbon and why?
- higher than carbon = electrolysis (K,Na,Ca,Mg,Al)
- below carbon (e.g iron oxide is reduced in a blast furnace to make iron) = heating with carbon (Zn, Fe, Sn, Cu)
- as carbon can only take away oxygen from metals less reactive than itself
66
How can copper oxide be reduced except for roasting in air and reducing with carbon?
- Copper (II) oxide can be reduced to copper by :
- heating it with methane or hydrogen in a reduction tube (has hole for excess gas burning and with a find with hole for tube to put gas in) over a Bunsen burner
- heating it with charcoal (fine power of carbon) in a test tube over a Bunsen burner
67
What is used to extract iron?
- blast furnace
- 3 raw materials :
- iron core (haematite)
- coke (mainly made of heating carbon without air)
- limestone (purifies the iron)
68
What is step one of extracting iron using the blast furnace?
- Coke burns in hot air to make CO2
| - C(s) + O2 (g) —> CO2
69
What is step two of extracting iron using the blast furnace?
- coke reduces the CO2 to make CO (carbon monoxide)
| - C (s) + CO2 (g) —> 2CO (g)
70
What is step three of extracting iron using the blast furnace?
- carbon monoxide reduces iron (III) oxide to iron at around 1500 C
- 3CO (g) + Fe2O3 (s) —> 3CO2 (g) + 2Fe (l)
71
What is wrong with the liquid iron extracted at the end of stage 3?
- has a lot of impurities (sandy impurities)
- or the properties of iron will be altered from what we want
- we use limestone (mostly calcium carbonate) to remove the impurities in 2 stages
72
Why would there be impurities in a blast furnace reaction with iron?
- there may be other oxides present with can be reduced with carbon as they’re less reactive than carbon
- this means it would be impure
73
What is stage 1 of using limestone to remove impurities from liquid iron?
- calcium carbonate is decomposed in high temp = breaks down in heat
- CaCO3 (s) —> CaO (s) + CO2 (g)
74
What is stage 2 of using limestone to remove impurities from liquid iron?
- Calcium oxide reacts with silica (SiO2) to form calcium silicate (CaSiO3)
- CaO (s) + SiO2 (g) —> CaSiO3 (l) - silica is the impurity
75
How can the molten iron be separated from the calcium silicate?
- molten calcium silicate is called slag and its less dense than the iron so the iron can be run off separately (iron is below it) in the blast furnace
76
What is aluminium ore called?
- Bauxite
| - aluminium = usually found as aluminium oxide = Al2O3
77
How is aluminium extracted and why?
- electrolysis (more costly process than reduction with carbon)
- as it’s more reactive than carbon
78
What is needed in electrolysis?
- need liquid/ solution (molten compound)
- once metal melted = electric current passed through it
- metal is discharged at cathode and the non metal at anode
79
What happens in electrolysis of bauxite?
- Al2O3 has m.p of 2072 C (very hot) so it’s expensive to melt which is why it’s dissolved in molten cryolite (allows electrolysis to happen at 950C) = ions are free to move
- electrolysis cell = steel lined with graphite = cathode / blocks of graphite = anode
- aluminium and oxygen formed
80
What is produced at each electrode in the electrolysis of bauxite and what are their half equations?
- aluminium formed at cathode= sinks to bottom of cell and is siphoned off
- Al^3+ + 3e- —> Al (reduction = gain e-)
- oxygen produced at anode where it reacts with graphite resulting in them being burnt way over time and requiring periodic replacemet= CO2 - 20^2- —> O2 + 4e- (oxidation = lose e-) = oxygen made
- C + O2 —> CO2 = reacts with graphite (carbon) = CO2
81
Why does copper need to be purified using electrolysis?
- copper = easily extracted by reduction with C (ore is heated in furnace = smelting)
- but copper produce d this way = impure so doesn’t conduct electricity = not very useful as most copper = used for electrical wiring
- electrolysis used to purify it (expensive) = produces pure copper with is a good conductor
82
How is copper purified using electrolysis?
- cathode (-) starts off as thin piece of pure copper and more copper adds to it
- anode ( +) is a big lump of impure copper which dissolves
- electrolysis is copper sulfate solution with Cu+ ions
- sludge = impurities in copper
83
What is acid mine drainage?
- abandoned mines flow with water
- oxidation of metal sulfides to sulfuric acid
- acid then reacts with metal ores, creating a soluble metal compound
- which are carried to the water as it drains from the mines into water systems
84
What do we need to use low-grade ores?
- supply of some metal rich ores (copper) = limited
- demand for metal is growing so may lead to shortages in the future
- scientists = looking into ways to extract metal from low grade ores (only small amount of metal) or from waste produced when metal extracted
85
What are the biological methods (use living organisms) to extract metals?
- bioleaching - uses bacteria to separate metals from their ores
- phytoextraction - growing plants in soil that contain metal compounds as the metal ions can accumulate in their roots, shoots and leaves
86
Give an example of bioleaching:
- copper can be separated from copper sulphide when:
- bacteria oxides iron (II) and sulphide ions using the energy transferred from the bonds= forming sulphuric acid when O and H2O present
- sulphuric acid breaks down copper sulfide ores to release the Cu(II) ions
- copper turns into a leachate (solution produced by the process - has Cu ions) has metal ions = extracted by electrolysis/ displacement with a more reactive metal (iron)
87
What are the advantages and disadvantages of bioleaching?
Advantages:
- low grade ores can be used
- cheaper than traditional mining/ processing
- bacteria occur naturally and don’t need special treatment
- doesn’t release sulphur dioxide in the atmosphere
Disadvantages
- slow
- toxic substances may be produced
88
What is the process of phytoextraction?
- crop is grown in soil containing low grade ores/ mine waste
- add complexing agent to ten soil to make it easier for plants to absorb the metal ions (metal ions build up in plant)
- plants are harvested , dried and then burnt in a furnace
- ash produced has high metal concentration = metal is extracted from ash as if it were a high grade ore (electrolysis/displacement reactions)
89
What are the advantages and disadvantages of phytoextraction?
Advantages
- cheaper than traditional mining and processing
- less waste
- small energy transfers
- close to carbon neutral (release co2 when burning = co2 absorbed for photosynthesis when growing)
Disadvantages
- slow
- crops may need replanting and harvesting for years before all the metal is removed from the soil
90
What is an alloy?
- mixture of two or more diff metals (brass and bronze)
- mixture of metal and non metal (steel)
- make them more useful than pure metal
91
What is steel an alloy of?
- alloy of iron and carbon
92
What are the uses of steel?
- girders, bridges, buildings, cars, saucepans, engine parts
93
What is brass an alloy of?
- alloy of copper and zinc (copper is soft as a metal)
94
What are the properties of steel?
- harder than iron
- stronger than iron (as long as amount of carbon doesn’t get more than 1%)
- iron rusts (corrodes) quickly on its own but steel is less likely to rust
95
What are the uses of brass?
- used for musical instruments (trumpets), coins, fixtures and fittings (screws, springs)
96
What is bronze an alloy of?
- alloy of copper and tin
97
What are the uses of bronze?
- bronze = bells & ship propellers (don’t get out of shape easily) and ships in saltwater (corrosion resistant) and springs, motor bearings and sculptures
98
What is solder an alloy of?
-alloy of tin and copper (m.p= 227 C) or lead and tin (indefinite m.p)
99
What are uses of solder?
- copper pipes/components in electrical circuits - flows into gaps to fill them and it conducts electricity
- low m.p so doesn’t melt rest of circuit components
100
What are the properties of brass?
- copper (soft metal) plus zinc makes brass strong & hard to bend
- good conductor, resists corrosion, strong and harder than Cu and Zn
- more resistant to corrosion than copper and tin
101
What is duralumin an alloy of?
- alloy of mostly aluminium (94%) and copper (6%) and maybe small amount of magnesium/ magnesium
102
What are the uses of duralumin?
- useful for parts of aeroplanes and aircraft as strong and light
103
What are the properties of bronze?
- harder and stronger than tin
| - more resistant to corrosion than copper or tin
104
What are the properties of solder?
- it doesn’t have a definite m.p but solidifies as it cools down
- used for joining metal things together
- relatively low m.p so you can melt it without melting other things in the circuit
105
What are the properties of duralumin?
- low density alloy and much stronger than Aluminium
106
What is corrosion?
It’s the reaction of a metal with substance in its surroundings
107
How does silver corrode?
- doesn’t react easily with oxygen but if H2S (hydrogen sulphide - made by bacteria) is present, it reacts with silver when O2 and H2O are also present to make a substance called silver sulphide (Ag2S)
108
What metals that don’t corrode?
- gold and platinum (used in jewellery)
| - other metals can corrode in the presence of oxygen and water to form their metal oxides (except iron which rusts)
109
When will iron rust?
- comes into contact with water and air after a while it rusts =only materials with iron can rust
- iron + water + oxygen —> hydrated iron (III) oxide
- the hydrated iron (III) oxide = flakes off surface of metal easily = exposes fresh metal underneath = can continue until iron/ steel obj is completely corroded away
110
Why type of reaction is the rusting of iron?
- redox reaction
- iron loses e- when reacting with O2 and each Fe atom loses 3e- to become Fe^3+ = iron is oxidised
- simultaneously = O2 gains e- when reacting with Fe & each O2 atom gains 2e- to become O^2- = oxygen is reduced
111
How can you investigate rusting?
- set up 3 boiling tubes with steel nail in each
- 1st tube = anhydrous calcium chloride (CaCl) = absorbs water keeping the nail dry
- 2nd tube = boiled water (no dissolved O2), and a bung = stops air getting back in
- 3rd = exposed to air and water
- observations = 1st (air, no water) = no rust, 2nd (water, no air) = no rust, 3rd (water and air) = rust
- oxygen and water needed for rusting to occur
112
What are the three ways of reduction rusting?
- paint the surface
- coat with coil, grease /plastic
- plating with zinc or tin
113
How can oil, grease and paint reduce corrosion?
- prevent corrosion by coasting the metal with a barrier which keeps the waters/ O2 or both out
- painting is ideal for large and small structures = also nice and colourful
- oiling / greasing has to be used when moving parts are involved = bike chains
114
How does a tin coating protect steel from eroding?
- tin plating = coat of tin applied to object/ electroplating steel with tin
- acts as barrier stopping water & oxygen from reaching surface of metal underneath
- only works as long as tin coating remains intact = if scratched to reveal some of the metal below = start to corrode
- food cans are plated inside with tin BUT it’s less reactive than iron so the damage occurring in the tin plating will corrode the iron/ steel quickly
115
What is the sacrificial method?
- place a more reactive metal with whatever you don’t want to corrode and the water/ oxygen will react with the sacrificial metal instead
116
How is the sacrificial method used in rusting?
- more reactive metal loses electrons more readily and is readily oxidised than iron so it has to be more reactive than iron
- therefore we use blocks of magnesium which can be bolted to less reactive metals so it corrodes first
- this is used on ship hulls and underground pipes
117
What is galvanising?
- metal (iron) is dipped into molten zinc to coat it and prevent rusting
- zinc is used as sacrificial protecting as it’s more reactive than iron and loses electrons more quickly and acts as a barrier
- steel buckets and corrugated iron roofing are often galvanised
118
What is polymerisation?
- reactions involving diff monomers to make a wide variety of polymers
- diff polymer = diff properties
119
What are high density and low density polymers used for?
- high density = strong and rigid = used to make water pipes
- low density = light and stretchy = plastic bags and sneezy bottles
120
What are polystyrene foam and heat resistant polymers used for?
- polystyrene foam = packaging to protect breakable things and as thermal insulator
- heat resistant polymers = melamine resin and polypropene = used to make plastic kettles
121
How are ceramics generally made?
- made by baking substances such as clay to produce a brittle, stiff material
123
What are the properties of ceramics?
- hard, non metallic materials which have metals and non metals combined to form a giant ionic lattice/ giant covalent structure
- made of oxides so very unreactive
- high melting point, hard, stiff, brittle
- poor conductors of electricity and heat
124
Give examples of ceramics:
- bricks, bone china , porcelain, glass
125
How is most glass made?
- most is soda lime glass made by heating limestone, sand and sodium carbonate (soda) (basically sand)until they melt then it cools = glass
- transparent, strong and can be moulded when hot and brittle when thin
- when sand melts and cools = forms giant irregular structure without crystals
126
How is porcelain and china made?
- heating clay to high temp, coating in glaze and then reheating
127
What are the properties needed for an overhead electrical cable?
- good conductor, lightweight and strong, corrosion resistant
- copper = good but low tensile strength = not as strong when stretched as Al and has high density
- Al is chosen as better conductor and light than steel, although not as strong
128
What is a composite?
- It’s made from two materials, the reinforcement is embedded into another (binder/matrix)
- properties are different from material it contains
129
How is pottery and bricks made?
- made from clay
- clay is a mineral formed from weathered and decomposed rock
- clay is soft when dug up = easy to mould into shapes for pottery/ bricks
- can be hardened by firing with at very high temp = ideal as building material as can withstand the weight of lots more brick on top
- clay heated to high temp = tiny crystals form which are joined together by glass
130
What is cob and where is it used?
- clay, sand, straw and water and dried
- has similar properties to reinforced concrete
- used in housing (using available resources)
131
What is polyester-cotton and where is it used?
- cotton is lightweight, comfortable, but not hard wearing
- polyester- cotton is made by wearing cotton thread with polyester fibre, an artificial polymer
- polyester fibre = comfortable, harder wearing than cotton and easier to wash and dry
132
What is fibreglass and where is it used?
- has fibres of glass embedded in matrix of a polymer
- low density but very strong
- used in skis and boats
133
What is carbon fibre and where is it used?
- made using carbon atoms bonded together to make carbon fibres/ carbon nanotubes held together in polymer resin matrix
- expensive to make but strong and light
- used for aerospace and sports car manufacturing
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What is concrete and where is it used?
- composite from aggregate (mixture of sand and gravel) embedded in cement, which is blinded with water
- has high compressive strength = doesn’t break if squashed = good for foundations (building materials)
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What is KEVLAR and where is it used?
- KEVLAR - based composites we made from KEVLAR which is often used as an ingredient in composite materials
- adds a lot of strength without much weight
- used in cycling helmets, tennis racquets and ropes
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What is steel- reinforced concrete and where is it used?
- Concrete has low tensile strength so beams made of just concrete crack but steel has high tensile strength
- steel rods are embedded into concrete to make steel - reinforced concrete with high compressive and tensile strength
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What is plywood and where is it used?
- to increase strength of wood we stick together sheets of thin wood at 90 degrees to each other = PLYWOOD
- more stronger as it can’t crack down one plane
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What properties of polymers make them best suited to their job?
- polymers = flexible (bend without breaking)
- easily be moulded into shapes
- cheaper than other materials and less dense than most metals/ ceramics
- thermal and electrical insulators
- but can degrade/ break down over time so don’t last as long as those made from other materials
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What properties of ceramics make them best suited to their job?
- insulators of heat and electricity
- more brittle and stiff than other materials
- strong and hard wearing
- don’t degrade or corrode like other materials so last a lot longer = this is why we have glass windows instead of plastic
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What properties of metals make them best suited to their job?
- good conductor of electricity and heat
- malleable (formed into variety of shapes)
- some metals corrode easily but products made from corrosion resistant metals can last a long time
- less brittle than ceramics/ polymers so likely to deform but stay in one piece but other materials can shatter
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What properties of composites make them best suited to their job?
- composites have diff properties based on the matrix/ binder and reinforcement
- combination of component materials can be altered so they can be designed to have a specific purpose
- disadvantage = much more expensive to produce than other materials
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What are LCA?
- life - cycle assessment = they are a ‘cradle to grave’ analysis of the impact of making, using and disposing of a manufactured product and works out the potential environmental impact
- used to identify stages to improve on/ alternate materials that can do same job = if production = 25%, use = 70% and disposal = 5% then try to improve its use
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What is meant by cradle, use and grave?
- cradle = how raw materials are obtained and processed to make useful material, what materials, energy and water used in manufacturing
- use = energy needed to use the product (e.g. electricity for computer), water and substances needed to ainrain the product (cleaning and manding)
- grave= energy needed to dispose of product, space needed to dispose
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What should an LCA include data about?
- sustainability
- environmental impact
- lifespan of a product
- how much can be recycled
- disposal including ease of decomposition of materials
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What needs to be considered when choosing a material?
- metals have to be mined and extracted from their oes = need lots of energy and cause a lot of polution
- raw materials for chemical manufacture often come from crude oil which is a non - renewable resources and the supplies are decreasing and obtaining it from the ground and refining it into useful raw material needs lot of energy and generates pollution
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What needs to be considered when manufacturing a product?
- manufacturing uses a lot of energy and other resources
- causes pollution ( harmful gases - CO2 or liquids - HCl)
- need to know about the wate products and how to dispose of them
- some waste = recycled and turned into useful chem = reducing amount that pollutes environment
- most chem need water - make sure they don’t put polluted water back into environment at the end of process
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What needs to be considered when using the product?
- using material can also damage environment
- paint gives off toxic fumes
- burning fuels releases greenhouse gases & other harmful substances
- fertilisers can leach into streams and rivers and cause damage to ecosystems
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Why is brass stronger than copper but more brittle?
- addition of other components to a metal disrupts its regular lattice of a metal nuclei = layers of metal can’t slide over each other as easily
- alloy has more strength as the layer can’t over move each easily so the rigidity of metal structure increases
- alloy is more brittle as nuclei in alloy are not all the same size so if layers of atoms move, the alignment of the nuclei will not be favourable and will cause repulsive forces to form = causes metal to break apart
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What needs to be considered when disposing a product?
- products often disposed of in a landfill site at end of their life
- takes up space and can pollute land and water
- products might be incinerated (burnt) = air pollution
- can be recycled
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What is the impact of plastic on the environment?
- it doesn’t break down into the environment
| - fish eat bags and die, birds eat plastic and die and plastic waste goes to massive areas
151
Why should we recycle?
- if not recycled , it goes to landfill sites
- but recycling conserves raw materials and energy resources, means less waste and harmful substances into the environment
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What does of extracting raw materials use?
- take large amounts of energy lots of which come from burning fossil fuels
- fossil fuels = running out so important to conserve them and burning them contributes to acid rain and climate change
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How much energy does recycling use compared to extraction?
- recycling material uses a small fraction of the energy that is needed to extract and refine material from scratch
- energy isn’t come cheap so recycling saves money
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How can recycling be useful in terms of fossil fuels and pollution?
- finite amount of raw materials so recycling can conserve these resources
- recycling metal cuts down on the amount of rubbish that gets sent to landfill which takes up space and pollutes the surroundings
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What’s the most cost effective metal to recycle?
- aluminium
- if you didn’t recycle it then you would need to mine more ores, transport it and extract it and then send it to landfill so for every 1kg of Al recycled you sage 95% of the energy needed to mine and extract fresh Al, 4kg of al ore and a lot of waste
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What are the factors that need to be considered when recycling?
- ease of collection and sorting of waste
- amount and type of byproducts released by recycling
- amount of energy involved at each stage enter
- cost of recycling compared to disposal in landfill/ incineration (burning)
- if it comes from renewable or non-renewable resources
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Why is recycling not an energy- free process?
- need to reprocess the materials into new forms
- if recycling material better than disposing of it and starting from scratch = requires comparison of how much energy is used for both these different processes
- so go for option with the lowest energy cost, least landfill consequences and non- renewable source
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Why does a recycled material have to be used differently?
- only can recycle materials a finite no. of times so if recycled material has lower quality than original it has to be used differently
- e.g paper can only usually be recycled a few times before it becomes useless = often used for toilet paper/ cardboard rather than high quality printing paper
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What is the process of recycling for metals, paper, glass and polymers?
- all materials are collected and sorted
- metals = melted and poured into moulds to produce ingots
- paper = mixed with water, cleaned, rolled and heated to make newspaper
- glass = sorted into diff colours, melted and moulded into new objects
- polymers = melted and formed into new objects
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Why can polypropylene, polystyrene and all other resins and multi-materials not be recycled?
- due to the mixture of compounds these plastic types are hard to recycle and note generally recycled in the UK
- used in packaging, takeaway containers and as plastics formed around meats and veg
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Name three polymers types that can be recycled and their uses:
- Polyethylene Terephthalate (PET) = water, fizzy drink, cooking oil bottles
- High density polyethylene (HEP) = milk/ juice bottles, bath and shower bottles, washing up liquid
- Polyvinyl Chloride (V)= usually in bottle form (not common nowadays)
162
What are the properties needed for a material for an insulator?
- must prevent electric current passing from cable to pylon = poor conductors needed
- Poly(propene) = tough and flexible polymer and poorest conductor and lowest tensile strength so snaps easily when stretched, also has lowest compressive strength = squashes easily
- Porcelain = lower resistance than glass but has higher compressive strength so it’s the most suitable for insulator when cables = fixed on top of structure
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Why should we recycle plastics?
Crude oil is non-renewable
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What are the properties of high density polymers?
- strong and not flexible thus it can’t be squeezed
- this means that it can’t be used for bottles
- all bottles = low density polymers
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Why is extraction iron bad?
- releases harmful gases into the environment and uses a lot of energy
