Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

OCR Gateway A GCSE Chemistry > C6 - Global Challenges > Flashcards

C6 - Global Challenges Flashcards

You may prefer our related Brainscape-certified flashcards:
GCSE Geography - AQA flashcards AP® Chemistry flashcards GCSE Religious Studies - Edexcel Route B flashcards GCSE Religious Studies - Eduqas Route A flashcards GCSE Religious Studies - Edexcel Route A flashcards GCSE Religious Studies - Eduqas Route B flashcards Periodic Table flashcards Chemistry 101 flashcards Organic Chemistry 101 flashcards
1
Q

what are the 3 essential elements needed by plants

A
  • nitrogen
  • phosphorus
  • potassium
    > plants don’t grow well if these are limited
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are some symptoms of mineral deficiencies in plants

A
  • poor growth
  • discoloured leaves
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what are fertilisers

A
  • substances that replace the essential elements used by plants as they grow
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what conditions must fertilisers be in, so that plant roots can easily absorb them

A
  • ions in water soluble form
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what ions are commonly found in fertilisers containing all 3 essential elements

A
  • Nitrogen: nitrate ions (NO 3-) and ammonium ions (NH4+)
  • Phosphorous: phosphate ions (PO4 3-)
  • Potassium: potassium ions (K+)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what are NPK fertilisers

A
  • fertilisers that provide all 3 essential elements in the form of water soluble compounds
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what are some examples of NPK fertilisers

A
  • ammonium nitrate NH4NO3
  • ammonium sulfate (NH4)2 SO4
  • ammonium phosphate (NH4)3 PO4
  • potassium nitrate KNO3
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

name the raw materials needed to make ammonium sulfate

A
  • sulfur (makes sulfuric acid)
  • natural gas
  • air (all 3 make ammonia)
  • water
    > ammonia + sulfuric acid —> ammonium sulfate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

name the raw materials needed to make ammonium phosphate

A
  • phosphate rock
  • sulfur —–> phosphoric acid
  • natural gas
  • air —–> ammonia
  • water
    > ammonia + phosphoric acid —> ammonium phosphate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

how can potassium sulfate be made in the lab

A
  • pour dilute potassium hydroxide into conical flask + add phenolphthalein indicator
  • add dilute sulfuric acid from a burette until neutralised
  • add activated charcoal to remove indicator, then filter out to remove
  • warm filtrate to leave crystals behinds (don’t heat to dryness)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

how can ammonium sulfate be made in the lab

A
  • pour dilute ammonia solution into conical flask + add methyl orange indicator
  • add dilute sulfuric acid from burette until neutralised
  • at the end-point add a little extra ammonia solution to ensure the reaction is complete
  • add activated charcoal to remove indicator + filter to remove
  • warm the filtrate leaving crystals behind (don’t heat to dryness)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is a batch process

A
  • when you make a small amount of substance at a time and once it’s made you stop the reaction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is a continuous process

A
  • when large amounts of substances are made and go on continuously without the reaction being stopped
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is the Haber Process

A
  • produces ammonia from nitrogen and hydrogen
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is the equation for the Haber process

A

Ns(g) + 3H2(g) <—–> 2NH3(g)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what conditions are used to carry out the Haber Process

A
  • temp of 450 degrees Celsius
  • pressure of 200 atmospheres (20 MPa)
  • iron catalyst
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

why is the pressure in Haber process considered to be a compromise

A
  • it’s high enough to produce a reasonable equilibrium yield
    > as equilibrium shifts to the right side because there’s less moles of gas so more product
  • however it’s not too high for it to be hazardous and expensive
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

why is the temperature in Haber process considered to be a compromise

A
  • it’s low enough for a reasonable equilibrium yield
    > because forward reaction is exothermic so to counteract equilibrium shifts to the left, decreasing ammonia yield
  • however it’s high enough for a reasonable rate of reaction + for the catalyst to work efficiently
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what are the raw materials for the Haber Process

A
  • natural gas
  • air
  • steam
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

how is nitrogen manufactured to be used in the Haber process

A
  • nitrogen is manufactured by the fractional distillation of liquefied air
    > air is 78% nitrogen
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

how is hydrogen manufactured to be used in the Haber Process

A
  • hydrogen is manufactured by reacting natural gas (mostly methane) with steam
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what other conditions are chosen for Haber process

A
  • liquefying ammonia (letting gas cool + turn to liquid)
    > conc of NH3 decrease so to counteract equilibrium shifts to right to increase NH3 yield
  • recycling the unreacted hydrogen + nitrogen
  • both of these improves the yield to around 97%
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what is the contact process

A
  • an important process in the formation of sulfuric acid
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what is sulfuric acid used for

A
  • making fertilisers
  • oil refining
  • metal extraction
  • making paints + polymers
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what are the 3 raw materials needed for making sulfuric acid

A
  • sulfur
  • air (source of oxygen)
  • water
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what step process is sulfuric acid synthesised in

A
  • 3 step process
    > including the contact process
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

what is stage 2 in the synthesis of sulfuric acid

A
  • the contact process
    > sulfur dioxide and oxygen react to produce sulfur trioxide
    sulfur dioxide + oxygen —> sulfur trioxide
    2SO2 + 2O2 <—> 2SO3
    > energy change = -144kj/mol = exothermic
    > reversible reaction because double arrow
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

what is stage 1 in the synthesis of sulfuric acid

A
  • sulfur burns in air to produce sulfur dioxide
    sulfur + oxygen —> sulfur dioxide
    S(s) + O2(g) —> SO2(g)
    > energy change = -297kj/mol = exothermic
    > not reversible as single arrow
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

what conditions are used for the contact process (stage 2)

A
  • pressure of 2 atmospheres (200 kPa)
  • temperature of 450 degrees Celsius
  • vandium oxide catalyst (V2O5)
    > under these conditions equilibrium yield is around 96%
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

why is the pressure chosen for Contact process a compromise

A
  • increased pressure will push equilibrium to the right with less moles of gas
    > however, in this reaction equilibrium is already so far to the right that we don’t need to spend more money on increasing the pressure
    > the pressure is enough
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

why is the temperature a compromise for the contact process

A
  • forward reaction is exothermic so to oppose the change the equilibrium will shift in the endothermic direction
    > the temperature chosen is a compromise as it’s low enough for a reasonable equilibrium yield but it’s high enough for a reasonable rate of reaction + for catalyst to work
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

what are the hazards in stage 3 of the synthesis of sulfuric acid + how can they be controlled

A
  • reaction between sulfur trioxide + water = very exothermic + produces hazardous acidic mist
  • so stage 3 is carried out in 2 steps:
    > 1. sulfur trioxide reacts with concentrated sulfuric acid to make a compound called oleum
    H2SO4 + SO3 –> H2S2O7
    > 2. the oleum is added to water to produce sulfuric acid as a final product
    H2S2O7 + H20 –> 2H2SO4
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

what is stage 3 in the synthesis of sulfuric acid

A
  • sulfur trioxide is converted into sulfuric acid
    > sulfur trioxide + water —> sulfuric acid
    SO3 + H2O —> H2SO4
    > not reversible
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

what is an ore

A
  • a rock or mineral that contains enough metal (or metal compound) to make it economical to extract the metal
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

give examples of some ores + metal compounds found in the ore

A
  • malachite = copper carbonate
  • bauxite = aluminium oxide
  • haematite = iron (III) oxide
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

what extraction methods are there to extract metals from their ores

A
  • essentially all metals could be extracted using electrolysis but electricity is expensive
    > instead, metals less reactive than carbon can be extracted by heating their compounds with carbon / carbon monoxide
    > as carbon (more reactive) can displace the oxygen
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

how is copper extracted from an ore

A

copper can be extracted from copper(II) sulfide in 2 stages:
- stage 1- first the 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 - the copper(II) oxide is heated with carbon
> copper(II) oxide + carbon —> copper + carbon dioxide
2CuO(s) + C(s) —> 2Cu(s) + CO2(g)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

what is stage 2 in copper extraction from ore, an example of

A
  • redox reaction
    > copper(II) oxide loses oxygen (reduced)
    > carbon gains oxygen (oxidised)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

what other methods can be used to reduce Copper(II) oxide to copper

A
  • by heating it with methane / hydrogen
    > copper oxide + hydrogen —> copper + water
    > copper oxide + methane (CH4) —> copper + carbon dioxide + water
    > methane contains carbon + hydrogen
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

what are the unreactive metals

A
  • silver
  • gold
  • platinum
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

what are native elements

A
  • elements found in pure form in the earth’s crust
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

what is a blast furnace used for

A
  • to extract iron from it’s core
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

what raw materials are added to the top of the blast furnace

A
  • iron ore (haematite) - contains iron(III) oxide
  • coke - mostly carbon + made by heating coal in absence of air
  • limestone - mostly calcium carbonate - removes impurities
    > additionally, hot air is forced in at the bottom of the blast furnace
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

what is a reducing agent

A
  • a substance which causes something to be reduced so they lose oxygen
    > reducing agents get oxidised as they gin oxygen
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

what is the main reducing agent in the blast furnace

A
  • carbon monoxide
    > formed when coke reacts with carbon dioxide
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

what is stage 1 in the extraction of iron in a blast furnace

A
  • coke burns in the hot air making carbon dioxide
    C(s) + O2(g) —> CO2(g)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

what is stage 2 in the extraction of iron in a blast furnace

A
  • more coke reduces the carbon dioxide, making carbon monoxide
    C(s) + CO2(g) —> 2CO(g)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

what happens in the blast furnace once iron(III) oxide gets reduced to iron

A
  • the molten iron trickles downwards in the blast furnace
    > however it contains sandy impurities from iron ore
    > this can be removed using limestone (calcium carbonate)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

what is stage 3 in the extraction of iron in the blast furnace

A
  • carbon monoxide reduces iron(III) oxide to iron at around 1500 degrees Celsius
    3CO(g) + Fe2O3(s) —> 3CO2(g) + 2FE(l)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

what happens in stage 4 in the extraction of iron in the blast furnace

A
  • calcium carbonate decomposes in high temperatures forming calcium oxide and carbon dioxide
    CaCO2(s) —> CaO(s) + CO2(g)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

what happens in stage 5 in the extraction of iron in the blast furnace

A
  • the calcium oxide formed reacts with silica from the sandy impurities to form calcium silicate (slag)
    CaO(s) + SiO2(g) —> CaSiO3(l)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

what is the final steps of the extracting iron from a blast furnace after all 5 stages

A
  • molten calcium silicate (called slag) floats on molten iron
  • both iron + slag are removed separately at the bottom of the blast furnace
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

write balanced equations + small explanations for all the reactions taking place in the blast furnace when extracting iron

A
  1. C(s) + O2(g) —> CO2(g)
    > coke burns in air making carbon dioxide
  2. C(s) + CO2(g) —> 2CO(g)
    > more coke reduces carbon dioxide to carbon monoxide
  3. 3CO(g) + Fe2O3(s) —> 3CO2(g) + 2Fe(l)
    > carbon monoxide reduces iron(III) oxide to iron at around 1500 degrees Celsius
  4. CaCO3(s) —> CaO(s) + CO2(g)
    > calcium carbonate decomposes in high temperatures forming calcium oxide + carbon dioxide
  5. CaO(s) + SiO2(g) —> CaSiO3(l)
    > calcium oxide formed, reacts with silica from sandy impurities to form calcium silicate (slag)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

what are some uses of aluminium

A
  • can be used in pans, drink cans and cars
  • aluminium alloys have low density but are very strong so can be used in bicycles + aeroplanes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

what does aluminium naturally exist as

A
  • aluminium oxide
    Al2O3
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

what ore is aluminum found in

A
  • bauxite
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

what method is used to extract aluminium from it’s ore + why

A
  • electrolysis
  • because aluminium is more reactive than carbon so must be extracted through electrolysis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

where is the molten mixture of aluminium oxide + cryolite contained

A
  • huge electrolysis cell
    > made from steel, lined with graphite
    > graphite lining acts as the cathode
    > huge graphite blocks act as anode
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

electrolysis only works if the compound is ____ or ______

A
  • molten
  • in solution
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

what are problems with the electrolysis of just aluminium oxide

A
  • aluminium oxide is insoluble in water + has a very high melting point (2050)
    > it would be very expensive to heat it to this temp
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

how can you reduce the melting point of aluminium oxide in order to carry out electrolysis

A
  • by adding an ionic compound called cryolite
    > cryolite has a much lower melting point
    > this allows electrolysis to happen at about 950
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

during electrolysis of aluminium oxide, what is produced at the anode + cathode + give half equations

A
  • aluminium is produced at the cathode where it gains electrons (reduction)
    Al3+ + 3e- —> Al
  • oxygen is produced at the anode where it loses electrons (oxidation)
    2O2- —> O2 + 4e-
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

during the electrolysis of aluminium oxide, what does the oxygen react with

A
  • the oxygen reacts with the hot graphite anodes, making carbon dioxide
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

what is the difference between high grade ore and low grade ore

A
  • high grade ore = high metal content
  • low grade ore = low metal content
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

how can bacteria produce sulfuric acid

A
  • by oxidising iron(II) ions + sulfide ions
    > the sulfuric acid forms in the presence of water + oxygen
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

what are the 2 biological methods of metal extraction

A
  • bioleaching
  • phytoextraction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

outline how bioleaching works

A
  • bacteria can be used to produce sulfuric acid by oxidising iron(II) ions + sulfide ions
    > in the process, sulfuric acid forms in the presence of water + oxygen
  • the sulfuric acid produced can break down copper sulfide ores (and other metals) releasing copper(II) ions along with other metal ions
49
Q

what are the advantages of bioleaching

A
  • cheaper than traditional mining
  • allows metals to be extracted from low grade ores
  • bacteria occur naturally + don’t need any special treatment
  • doesn’t release harmful sulfur dioxide into atmosphere
49
Q

what are the disadvantages of bioleaching

A
  • very slow process
  • toxic substances produced sometimes
  • care must be taken to ensure toxic substances + sulfuric acid don’t escape into water supplies + soil
50
Q

outline how phytoextractions works

A
  • plants absorb dissolved ions through their roots
    > some plants are particularly good at absorbing certain metal ions, which then accumulate in their roots, shoots and leaves
  • a crop is planted in soil containing low-grade ore or mine waste
    > a ‘complexing agent’ may be added so plants can absorb the metal ions more easily
  • the plants are then harvested + burnt to ash - leaving behind a high concentration of the metal remaining
    > the metal can be extracted in normal way with any high grade ore
51
Q

what are advantages of phytoextraction

A
  • cheaper than traditional mining + processing
  • produces less waste
  • involves smaller energy transfers
  • closer to being a carbon neutral activity that can contribute to sustainable development
  • CO2 produced is absorbed by plants for photosynthesis as they grow
  • burning plants can generate electricity
52
Q

what are disadvantages of phytoextraction

A
  • slow
  • crops may need replanting + harvesting for several years before the available metal is removed from soil
  • burning plants release CO2
53
Q

what are alloys

A
  • mixtures of two or more elements
    > of which at least one is a metal
54
Q

what are 5 important alloys

A
  • steel
  • duralumin
  • solder
  • brass
  • bronze
55
Q

what main metal(s) are present in steel

A
  • iron
56
Q

what main metal(s) are present in duralumin

A
  • aluminium
  • copper
57
Q

what main metal(s) are present in solder

A
  • tin
  • copper
57
Q

what main metal(s) are present in brass

A
  • copper
  • zinc
58
Q

what main metal(s) are present in bronze

A
  • copper
  • tin
59
Q

what are some uses of steel

A
  • buildings
  • bridges
  • cars
59
Q

what are some uses of duralumin

A
  • aircraft parts
60
Q

what are some uses of solder

A
  • joining electrical components + copper pipes
61
Q

what are some uses of brass

A
  • musical instruments
  • coins
61
Q

why is solder’s property useful

A
  • the low melting point makes the metal useful for joining electrical components together without damaging them
61
Q

what are some uses of bronze

A
  • bells
  • ship propellers
61
Q

what key properties does bronze have + why are they useful

A
  • resists corrosion
  • stronger + harder than copper
    > makes it useful for ship propellers
    > also used to make bells + metal artwork
61
Q

what are some useful properties of steel

A
  • high tensile strength
  • ductile
61
Q

how does solder differ to pure tin + copper

A
  • solder have low melting points (227 C)
    > tin has 232 C
    > copper has 1085 C
61
Q

what key properties does brass have + why are they useful

A
  • good electrical conductor
  • resists corrosion - doesn’t react easily with water / air
    > these properties make brass useful for making pins for electrical plugs
61
Q

what is corrosion

A
  • the reaction of metal with substances in its surroundings such as air or water
61
Q

what metals don’t corrode

A
  • very unreactive metals such as gold or platinum
62
Q

does iron corrode

A
  • yes
    > when it corrodes it’s called rusting
63
Q

what type of reaction is rusting

A
  • redox reaction
    > iron is oxidised to hydrated iron(III) oxide
    iron + water + oxygen —> hydrated iron(III) oxide
63
Q

does silver corrode

A
  • doesn’t easily react with oxygen in air / water
    > but corrodes in presence of hydrogen sulfide to produce a thin layer of black silver sulfide
63
Q

what is rusting

A
  • the corrosion of iron
63
Q

how can prevent oxygen + water from reaching the surface of metals

A
  • painting the metal
  • coating with oil / grease / plastic
  • plating with zinc (galvanising)
  • plating with tin
63
Q

what is the word equation for the making of rust

A

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

63
Q

what is sacrificial protection

A
  • when a more reactive metal than iron is in contact with the less reactive metal
    > the metal ‘sacrifices’ itself to protect the less reactive metal (iron / steel)
63
Q

how does sacrificial protection work

A
  • the more reactive metal is in contact with less reactive metal
  • more reactive metal corrodes first + protects the less reactive metal + in a way ‘sacrifices’ itself
    > overtime the metal plates corrode away and will need replacing
63
Q

what metals are commonly used for sacrificial protection

A
  • metals more reactive than iron
    > such as magnesium / zinc
63
Q

what is metal plating

A
  • a thin layer of metal can be plated over a structure of iron/steel, thus creating a protective layer between the air/water and the metal
    > creates a physical barrier preventing corrosion
64
Q

what is galvanising + how does it prevent corrosion

A
  • galvanising involves dipping the metal into molten zinc + once cooled and solidified the layer of zinc does 2 things
    > stops air/water reaching iron/steel below
    > acts as a sacrificial metals so the object is protected, even if zinc is damaged
64
Q

what is tin plating

A
  • tin plating involves electroplating the steel object with tin / dipping it into molten tin
    > e.g. inside steel food cans
65
Q

what are ceramics + examples

A
  • hard, non-metallic materials
    > e.g. brick, china, porcelain, glass
65
Q

how is glass made

A
  • by melting sand + allowing it to cool and solidify
65
Q

what are some typical properties of ceramics + why do they have them

A
  • high melting points
  • hard + stiff but brittle
  • poor conductors of electricity + heat
    > all of this is because ceramics contain metals + non-metals which combine to form giant covalent structures giving them these properties
65
Q

what is a disadvantage of tin plating

A
  • tin is less reactive than iron
    > so if damaged, the steel will act as a sacrificial metal for the tin + speeds up rusting even fasting than normal
65
Q

why are ceramics unreactive

A
  • because the compounds in ceramics are mostly oxides
66
Q

describe the structure of glass

A
  • has irregular giant structure
  • without crystals
  • usually transparent
67
Q

how are other ceramics (not glass) made

A
  • by heating clay to very high temperatures
    > tiny crystals form which are joined by glass
68
Q

why are china + porcelain usually coated in glaze

A
  • glaze forms a smooth, hard & waterproof surface
69
Q

what is a composite material

A
  • a material made from 2 or more materials combined, each with different properties
70
Q

what useful properties do cotton-polyester have + how do they differ to cotton and polyester individually

A
  • cotton-polyester is made by weaving cotton thread with polyester fibre, an artificial polymer
    > it’s comfortable, but harder wearing than cotton, and easier to wash and dry
  • cotton on the other hand is lightweight and comfortable to wear but not very hardwearing
71
Q

what does fibreglass consist of + what is it used for

A
  • fibreglass consist of glass fibres in resin
  • used for:
    > canoes
    > boats
    > surfboards
72
Q

what does carbon fibre consist of + what is it used for

A
  • carbon fibre consists of carbon fibres in resin
  • used for:
    > sports equipment
    > racing cars
    > aircraft part
  • it’s more expensive than fibreglass
73
Q

how do properties of steel-reinforced concrete compare to concrete + why is this useful

A
  • steel-reinforced concrete has high compressive strength + high tensile strength
  • concrete has high compressive strength + but low tensile strength
    > steel-reinforced concrete creates a composite material which is strong because it has high composite + tensile strength so wont squash or crack/break
74
Q

why do we recycle materials

A
  • to converse raw materials (e.g. metals)
  • reduce waste
  • avoid filling landfill sites
  • conserve energy resources (e.g. from fossil fuels)
  • reduce the release of harmful substances into atmosphere
  • avoid waste polluting oceans + seas
75
Q

what factors need to be considered when deciding if a product should be recycled

A
  • how easily the waste can be collected + sorted
  • cost of recycling compared to disposal in landfill or by incineration (burning)
  • amount + type of by-product released by recycling
  • amount of energy involved at each stage
76
Q

what is a life-cycle assessment

A
  • LCA is a ‘cradle-to-grave’ analysis of the impact of making, using, and disposing of a manufactured product
76
Q

what should LCA’s include data about

A
  • sustainability, including raw materials + energy
  • environmental impact, including waste products + pollution
  • lifespan of the product + whether any of it can be recycled
  • disposal, including how easily the materials decompose
76
Q

how are metals recycled

A
  • metals are melted + moulded into new blocks called ingots
76
Q

what are the stages in a products life

A
  • extracting + processing raw materials
  • manufacturing + packaging
  • use + operation during its lifetime
  • disposal at the end of its useful life, including transport + distribution
76
Q

why are life-cycle assessments carried out

A
  • to identify the stages that could be improved
  • to find alternative materials that might do the same job
76
Q

how is paper recycled

A
  • paper is mixed with water + cleaned + rolled + heated to make new paper
77
Q

how is glass recycled

A
  • glass is melted + moulded into new glass objects
77
Q

how are polymers recycled

A
  • polymers like plastic are melted + formed into new objects
77
Q

what 3 main substances make up the earth’s atmosphere

A
  • nitrogen 78%
  • oxygen 21%
  • argon 0.9%
    > trace amounts of other gas e.g. carbon dioxide (0.04%) + water vapour
77
Q

where did the earth’s early atmosphere come from

A
  • substances released by volcanic activities
78
Q

how old is the earth

A

4.54 billion yeas old

79
Q

what substances did the volcanoes release in early atmosphere

A
  • huge volumes of water vapour + carbon dioxide
80
Q

how did oceans form

A
  • as the earth cooled, the water vapour condensed to form oceans, leaving an atmosphere of mostly carbon dioxide
81
Q

after the oceans were formed what did the earth’s atmosphere contain

A
  • mostly carbon dioxide
    > contained small amounts of other gases like ammonia, methane and nitrogen
    > but little or no oxygen
82
Q

how did oxygen levels increase in the atmosphere

A
  • oxygen produced from photosynthesis helped remove any ammonia + methane in atmosphere by reacting with it
  • oxygen also reacted with metals, forming metal oxides
    > after a while, as most metals became oxidised, free oxygen began to accumulate in the atmosphere
82
Q

why has the atmosphere changed over time - increased levels of oxygen but decreased levels of carbon dioxide

A
  • through photosynthesis
    > plants + algae took in carbon dioxide from atmosphere and released oxygen
83
Q

how was the ozone layer created

A
  • eventually so much oxygen was produced that a protective layer began to form around the planet
    > this is now what we call the ozone layer - O3
    > ozone layer protected earth from UV rays
    > this led to evolution and growth of animals
84
Q

what are pollutants

A
  • substances which are released into the environment that may harm living things
85
Q
  • where are atmospheric pollutants released + what are they caused by
A
  • into the air
    > many are released as a result of burning fossil fuels
    > they include carbon monoxide,
    particulates, nitrogen oxides, sulfur
    dioxide
86
Q

how is carbon monoxide produced

A
  • during incomplete combustion when not enough oxygen is present:

hydrocarbon + not enough O2 (burn to produce) carbon monoxide fine particles

87
Q

what is carbon monoxide + what happens when inhaled

A
  • a toxic colourless gas, no smell / test
    > when breathed in it combines with haemoglobin which reduces the amount of oxygen that the bloodstream can carry
    > Co poisoning can cause drowsiness, difficulty breathing + even death
88
Q

in what circumstances is CO produced

A
  • during incomplete combustion of fuels containing carbon
    > when coal, wood, or natural gas are burned in poor supply of air
    > in vehicle engines
89
Q

what safety measures are taken to ensure CO can be detected

A
  • installing carbon monoxide detectors in homes etc
90
Q

what are particulates + how are they produced

A
  • particulates are small particles
  • they are produced in industrial process such as metal extraction
    > they are also produced during incomplete combustion + in vehicle engines
91
Q

what happens when particulates are inhaled

A
  • smallest particulates settle deep in the lungs when breathed in
    > causes diseases such as bronchitis + other breathing problems + increases chance of heart disease
92
Q

why does sulfur produce problems as a pollutant

A
  • when fuels are burnt, sulfur impurities are released
    > these react with oxygen to form sulfur dioxide gas
  • sulfur dioxide mixes with water in clouds, forming dilute sulfuric acid
    > when this acid rain falls it damages buildings + kills trees + living things
93
Q

how can you prevent acid rain

A
  • remove sulfur impurities from fuel before you burn it
  • sulfur gas can be removed from factories + chimneys using calcium oxide which neutralises the acidic oxides produced
94
Q

why does nitrogen cause problems as a pollutant

A
  • only at high temps in vehicle engines, nitrogen in the air react with oxygen gas producing nitrogen oxides
    > nitrogen oxides are toxic + trigger asthma attacks
  • can also lead to formation of acid rain
95
Q

why do acidic oxides cause problems

A
  • they can cause acid rain
    > acid rain destroys buildings especially limestone
    + can kill living thins in rivers + lakes and can kill trees
96
Q

what is the greenhouse effect

A
  • when greenhouse gases such as CO2 + methane absorb infrared radiation radiated by Earth’s surface, then emit it in all directions
    > this keeps the earth + its atmosphere warm enough for living things to exist
97
Q

how is carbon dioxide (greenhouse gas) released into the atmosphere

A
  • by combustion of fossil fuels
98
Q

how is methane (greenhouse gas) released into the atmosphere

A
  • from rice paddy fields
  • cattle
  • landfill waste sites
  • use of natura; gas
99
Q

what is the enhanced greenhouse effect + what does it lead to

A
  • the release of additional greenhouse gases by human (anthropogenic) activities has potential to cause an enhanced greenhouse effect which increases the temperature of the earths atmosphere
    > this global waring leads to melting ice caps + rising sea levels + climate change
    > climate change brings altered weather patterns, causing flooding + problems with farming + disease control
100
Q

what does global warming lead to

A
  • melting ice caps
  • rising sea levels
  • climate change
101
Q

what does climate change bring about

A
  • altered weather patterns causing:
    > flooding
    > problems with farming + disease control
102
Q

how can greenhouse gas emission be reduced into the atmosphere

A
  • reducing consumption of fossil fuels, by using biofuels
  • using renewable energy resources such as wind + solar energy to generate electricity
  • stopping CO2 escaping when fuels are used by using carbon capture
    > such steps are expensive but so are steps to protect against the effects of global warming
    > e.g. flood barriers, planting diff crops, designing buildings to withstand high winds
103
Q

how is carbon capture used to stop CO2 escaping when fuels are used

A
  • CO2 produced in power stations can be pumped deep underground into porous rocks + trapped there
    > this process is expensive + companies would need to increase cost of electricity o offset this extra cost
104
Q

how does build up of greenhouse gases lead to global warming

A
  • more IR radiation gets trapped than usual and as a result the energy leads to an increase in global temperatures - also known as global warming
105
Q

what is potable water

A
  • water which is safe for drinking
106
Q

what is a reservoir

A
  • an enlarged natural or artificial lake used as a source of water supply
107
Q

what is an aquifer

A
  • layer of rock which stores water underground
108
Q

what is desalination

A
  • the process of removing dissolved salts from water
109
Q

where does drinking water originally come from

A
  • water stored in lakes, reservoirs or aquifers
    > it may have also come from rivers or waste water
110
Q

water from all the sources (lakes, reservoirs, aquifers) contain microorganism and many different substances such as:

A
  • insoluble materials like leaves + particles from rocks and soil
  • soluble substances, including salts + pollutants such as pesticides + fertilisers
111
Q

how can we produce potable water

A
  • 2 main approaches depending on what type of water we’re dealing with
    > fresh water
    > salt water
112
Q

how is freshwater treated to produce potable water

A
  • there are a few steps:
    1. screening - removal of large insoluble objects
    2. settlement, coagulation, sedimentation - removal of smaller insoluble substances
    3. filtration - removal of any remaining insoluble substances
    4. chlorination - to kill any bacteria
    5. final checks - to ensure pH is neutral + add any useful chemicals like fluoride ions
113
Q

how is salt water treated to produce potable water

A
  • seawater contains very high concentrations of dissolved salts
    > to make this water potable, the salt must be removed, in a process called desalination
  • for small scale desalination, we use a process called ‘reverse osmosis’ which uses special ‘ultrafilters’ to filter out the salts
    > for large scale desalination, simple distillation is used

OCR Gateway A GCSE Chemistry (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions