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gcse chemistry > C6.1 - Metals > Flashcards

C6.1 - Metals Flashcards

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1
Q

Ore

A

= rock / mineral that contains enough metal to make it economical to extract the metal

(Value of metal > cost of extracting it)

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2
Q

List the different ores and the metal compound found in them

A
  • malachite: copper carbonate
  • bauxite: aluminium oxide
  • haematite: iron(III) oxide
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3
Q

Why are ores mined

A

To separate the metal compound from the other substances in the ore

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4
Q

What is used to determine what extraction method is used to obtain the metal from the pure metal compound

A

Depends upon the metals position in the reactivity series

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5
Q

What are the 2 extraction methods & when are they sued

A
  • electrolysis: metal more reactive than carbon

- heating: metal less reactive than carbon

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6
Q

why is heating preferred over electrolysis to extract metal

A

It is cheaper

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7
Q

Reactivity series (most -> least reactive)

A 
Potassium
Sodium
Calcium
Magnesium
Aluminium
Carbon
Zinc
Iron
Tin
Lead
Copper
Silver
Gold
Platinum
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8
Q

What are the 2 stages to extract copper from copper(II) sulfide

A

1: copper(II) sulfide ‘roasted’ in air
2: copper(II) oxide heated with carbon (/ methane / hydrogen)

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9
Q

Word & symbol equation for stage 1 of copper extraction

A

Copper(II) sulfide + oxygen —> copper(II) oxide + sulfur dioxide
2CuS (s) + 3O2 (g) —> 2CuO (s) + 2SO2 (g)

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10
Q

Word & symbol equation for stage 2 of copper extraction

A

Copper(II) oxide + carbon —> copper + carbon dioxide

2CuO (s) + C (s) —> 2Cu (s) + CO2 (g)

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11
Q

Why is stage 2 of copper extraction a redox reaction

A
  • copper(II) oxide loses oxygen = reduced, oxidising agent

- carbon gains oxygen = oxidised, reducing agent

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12
Q

Extracting copper experiment (PAG)

A
  • mix copper(II) oxide & charcoal in crucible
  • put lid on top (so powders don’t escape / air doesn’t get in causing carbon to burn during heating)
  • heat it strongly
  • after few mins, allow crucible to cool
  • when cool, transfer contents to breaker of water
  • copper sinks to bottom, excess charcoal suspended in water (top)
  • separate copper by washing it
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13
Q

Blast furnace

A

Industrial large reaction vessel for iron production (to extract iron from its ore)

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14
Q

Raw materials added at top of a blast furnace

A
  • iron ore (haematite)
  • coke
  • limestone (calcium carbonate)
  • hot air (forced into bottom)
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15
Q

Why are each of the raw materials needed in the blast furnace

A
  • haematite: source of iron
  • coke: source of carbon (coal heated without air)
  • limestone: purifies iron
  • hot air: source of oxygen
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16
Q

Temperature inside a blast furnace

A

Varies from
1900ºC at bottom
to 300ºC at top

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17
Q

3 stages of carbon reducing iron(III) oxide to iron in a blast furnace

A

1: coke burns in hot air, making carbon dioxide
2: more coke reduces carbon dioxide, making carbon monoxide
3: carbon monoxide reduces iron(III) oxide to iron at 1500ºC

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18
Q

Word & symbol equation of stage 1 of iron extraction

A

Coke (carbon) + oxygen —> carbon dioxide

C (s) + O2 (g) —> CO2 (g)

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19
Q

word & symbol equation of stage 2 of iron extraction

A

Coke + carbon dioxide —> carbon monoxide

C (s) + CO2 (g) —> 2CO (g)

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20
Q

word & symbol equation for stage 3 of iron extraction

A

Carbon monoxide + iron(III) oxide —> carbon dioxide + iron

3CO (g) + Fe2O3 (s) —> 3CO2 (g) + 2Fe (l)

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21
Q

What is used to purify the iron extracted & why

A
  • molten iron trickles down in blast furnace
  • contains sandy impurities from iron ore
  • removed using limestone (calcium carbonate)
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22
Q

How is the iron extraction purified

A
  • calcium carbonate decomposes at high temps
  • forms calcium oxide
  • calcium oxide reacts with silica (in sandy impurities)
  • forms calcium silicate
  • molten iron separates & molten calcium silicate(slag) floats on top
  • both iron & slag removed separately at bottom of blast furnace
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23
Q

Word & symbol equation for stage 1 of iron purification

A

Calcium carbonate —> calcium oxide + carbon dioxide

CaCO3 (s) —> CaO (s) + CO2 (g)

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24
Q

Word & symbol equation for stage 2 of iron purification

A

Calcium oxide + silica —> calcium silicate

CaO (s) + SiO2 (g) —> CaSiO3 (l)

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25
Q

What extraction method is used for aluminium, why

A

= electrolysis

More reactive than carbon

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26
Q

What ore is pure aluminium extracted from

A

Aluminium oxide, Al2O3

Found in the ore bauxite

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27
Q

Why can’t aluminium oxide undergo electrolysis

A

Electrolysis only works in solution / molten form

  • not solution: aluminium oxide doesn’t dissolve in water
  • not molten: very high melting point (2000ºC), too expensive to heat
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28
Q

Why is aluminium oxide dissolved in molten cryolite for electrolysis

A

Cryolite has much lower melting point than aluminium oxide (950ºC)

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29
Q

What is the huge electrolysis cell that holds molten mixture of aluminium oxide & cryolite made from

A

steel, lined with graphite

30
Q

What is the cathode (-) and anode (+) in the electrolysis of aluminium

A

Cathode: graphite lining
Anode: series of large graphite blocks

31
Q

What is produced at the cathode during electrolysis of aluminium, half equation

A

Aluminium

Al3+ + 3e- —> Al

32
Q

What is produced at the anode during the electrolysis of aluminium, half equation

A

Oxygen
2O2- —> O2 + 4e-

Then oxygen reacts with hot graphite anodes, producing carbon dioxide
O2 + C —> CO2

33
Q

Low grade ore

A

Ores that contain too little metal for traditional methods to be profitable

34
Q

Bioleaching

A

Biological method of metal extraction in which bacteria speed up reactions that release soluble metal compounds from metal sulfides

35
Q

How does bioleaching work

A
  • bacteria oxidise iron(II) & sulfide ions in low grade ores
  • bacteria use energy transferred for respiration
  • in the presence of water & oxygen
  • oxidised sulfide ions react with water to produce sulfuric acid
  • sulfuric acid breaks down other minerals in ore
  • releasing metal ions into solution
36
Q

Advantages of bioleaching over traditional mining for metals

A
  • cheaper
  • extracts metals from low-grade ores
  • occurs naturally
  • doesn’t require special treatment / conditions
  • doesn’t release harmful sulfur dioxide into atmosphere
37
Q

disadvantages of bioleaching over traditional mining for metals

A
  • slower
  • other toxic substances sometimes produced
  • toxic substances & sulfuric acid can escape into(contaminate) water supply & soil if not careful
38
Q

What part of the plant absorbed dissolved ions

Where are the absorbed metals stored

A

= through their roots

  • roots
  • shoots
  • leaves
39
Q

Phytoextraction

A

Biological method of metal extraction in which plants absorb metals through their roots & concentrate them in their cells

40
Q

Explain the process of phytoextraction

A
  • crop planted in soil containing low-grade ore
  • crop/plan absorbs metal ions through roots
  • crop/plant harvested
  • crop/plant burnt
  • burning increases concentration of metal in plant
  • metal remains in ashes
  • ash = high-grade ore, metal then extracted (smelted)
41
Q

Why may a complexing agent be added during phytoextraction

A

Helps plants absorb metal ions more easily

42
Q

Why is phytoextraction a carbon neutral process

A
  • carbon dioxide released when burned
    BUT
  • carbon dioxide absorbed during photosynthesis as they grow
43
Q

Advantages of phytoextraction over traditional mining of metals

A
  • cheaper
  • produces less waste
  • involves smaller energy transfers
  • more carbon-neutral activity
44
Q

Disadvantages of phytoextraction over traditional mining of metals

A
  • slower

- crops may need replanting & harvesting for several years before available metal removed / absorbed from soil

45
Q

Alloy

A

Mixture of 2 or more elements

At least 1 of which is a metal

46
Q

Properties of steel (& most other metals)

A
  • high tensile strength

- ductile

47
Q

List alloys & their typical uses

A
  • Bronze: bells, propellers for ships
  • Duralumin: aircraft parts
  • Steel: buildings, bridges, cars
  • Brass: musical instruments, coins
  • Solder: joining electrical components, pipes
48
Q

what are the main metals in each alloy

A
  • Bronze: copper & tin
  • Duralumin: aluminium & copper
  • Steel: iron
  • Brass: copper & zinc
  • Solder: copper & tin
49
Q

What properties of solder make it useful for joining electrical components without damaging them

A
  • low melting point = melt & flow into gaps between components
  • conducts electricity = allows current to pass between components
50
Q

Corrosion resistant

2 alloy examples:

A

= doesn’t react easily with water

  • brass
  • bronze
51
Q

Why can metals be stretched / bent

A
  • layers of metal atoms
  • slide over each other
  • as all atoms same size
52
Q

Why are alloys often stronger & harder than individual metals

A

Atoms in alloy are of different sizes

So difficult for atoms to slide over each other

53
Q

Why is brass useful for making pins for electrical plugs

A
  • contains copper, good conductor
  • corrosion resistant
  • strong
54
Q

Why is the alloy bronze useful for making propellers for ships

A
  • corrosion resistant
  • strong
  • hard
55
Q

Why can the alloy bronze be used for musically instruments & artwork

A

Molten bronze expands slightly as it solidifies

So can create details

56
Q

corrosion

A

Reaction of metal with substances found in its surroundings

57
Q

Explain the corrosion of silver:
What does it corrode in
Why does it turn black

A
  • doesn’t easily react with oxygen (in air/water)
  • does in presence of hydrogen sulfide, H2S (g)
  • when oxygen & water also present
  • corrodes silver, producing thin layer of black silver sulfide, Ag2S (objects turn black, need to be cleaned)
58
Q

What metals don’t corrode

Why

A
  • Gold, Au
  • Platinum, Pt

As very unreactive metals

59
Q

Rusting

A

Corrosion in which iron / steel reacts with oxygen & water to form hydrates iron(III) oxide (rust)

60
Q

Word equation for rusting of iron

A

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

Redox reaction, iron oxidised

61
Q

Why does the mass of iron/steel decrease during rusting

A
  • orange-brown rust (hydrated iron(III) oxide)
  • easily flakes off surface of object
  • exposing fresh metal underneath
  • rusting continues till iron / steel object completely corroded away
62
Q

Testing substances needed for rusting using steel / iron nails

A

Set up 3 boiling tubes:

1: iron/steel nail & anhydrous calcium chloride
2: iron/steel nail & boiled water
3: iron/steel nail & water
- bung tubes 1 & 2
- leave tubes for few days
- observe & record results

63
Q

What results are expected during the rusting experiment in each boiling tube, why?

A

1: no rust (anhydrous calcium chloride prevents water contacting nail but allows oxygen)
2: no rust (boiling removes all gases like oxygen from water but allows water)
3: rust (water & oxygen have access to nail)

64
Q

What substances cause rust

A
  • air (oxygen)

- water

65
Q

List methods used to stop air & water reaching surface of metal, preventing corrosion

A
  • painting
  • coating with oil, grease, plastic
  • plating with zinc (galvanising)
  • plating with tin
66
Q

Sacrificial protection

A

Rust prevention in which more reactive metal than iron / steel (magnesium, zinc) corrodes in preference to iron / steel

As more reactive metal corrodes first, protecting iron/steel

67
Q

How does sacrificial protection work in terms of electrons

A

During resting, iron atoms oxidised (loses electrons) to iron(III) ions
(Fe —> Fe3+ + 3e-)

more reactive metal = more easily loses electrons
So more readily oxidised than iron

68
Q

Metal plating

A

Layer of metal plated onto iron / steel object preventing air & water reaching iron / steel below

Eg. Galvanising

69
Q

Galvanising

A

Coating iron / steel with thin layer of zinc

70
Q

What does the layer of zinc in galvanising do

A
  • stops air & water reaching iron / steel below

- acts as sacrificial metal so object protected, even if zinc layer damaged (as more reactive than iron/steel)

71
Q

How is tin plating done

A
  • electroplating steel object with tin

- dipping it in molten tin

72
Q

Disadvantage of tin plating

A
  • tin less reactive than iron

- If tin layer damaged, steel acts as sacrificial metal for tin & rusts even faster than normal

gcse chemistry (10 decks)

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