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Chemistry AQA GCSE > C15 Using our resources > Flashcards

C15 Using our resources Flashcards

1
Q

what is rusting?

A

the corrosion of iron or steel

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2
Q

what conditions are needed for iron or steel to rust?

A

oxygen and water

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3
Q

what is the chemical name for rust?

A

ruse = hydrated iron (III) oxide

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4
Q

word equation for the rusting of iron

A

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

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5
Q

what is done to iron or steel to prevent them from rusting?

A

preventing water and oxygen from reaching the iron/steel by coating it with either:
- paint,
-a more/less reactive metal,
- oil or grease,
- plastic.

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6
Q

how does rust spread?

A
  • rust forms,
  • it is soft and flakes off the iron/steel,
  • exposing more iron/steel to the oxygen and water,
  • so more of it rusts.
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7
Q

what is sacrificial protection? why does it work?

A

sacrificial protection: coating iron/steel with a more reactive metal which reacts with the oxygen and water instead of the iron/steel itself, preventing it from rusting.
works because the more reactive metal has a stronger tendency than the iron/steel to give away electrons and form positive ions.

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8
Q

what is galvanisation?

A

coating iron/steel with zinc which is more reactive, so sacrificially protects it from rusting.

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9
Q

when is sacrificial protection often used?

A
  • used under harsh conditions e.g. in seawater,
  • protecting underground pipes,
  • when coating is likely to be scratched, e.g. commercial wheelie bins
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10
Q

give 2 alloys that are made using copper and one other metal

A
  • copper and zinc alloy makes brass,
  • copper and tin alloy makes bronze.
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11
Q

which 2 metals is bronze an alloy of?
what is it used for? why?

A

BROCT
- bronze is an alloy of copper and tin,
- used for statues, decorative items, ship propellers,
- because of its toughness and resistance to corrosion.

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12
Q

what is steel?

A

an alloy of iron with carbon and/or other elements

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13
Q

which 2 metals is brass an alloy of?
what is it used for? why?

A

BRACZ
- brass is a alloy of copper and zinc,
- used for taps, musical instruments and door fittings,
- because it is hard but workable: can be hammered into thin sheets and pressed into shapes.

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14
Q

give a property of aluminium alloys

A

low density

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15
Q

why are copper, aluminium and gold often alloyed with other metals?

A

to make them harder

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16
Q

why is gold often alloyed with copper?

A

so that it wears away more slowly

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17
Q

what is corrosion?

A

the destruction of materials by chemical reactions with substances in the environment

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18
Q

how to measure the proportion of gold in an alloy

A

divide the carat number by 24: e.g. 24 carat gold is 100% (pure), 18 carat gold is 75% gold.

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19
Q

describe the difference between the properties of low and high carbon steel

A

low carbon steel: softer and more easily shaped
high carbon steel: strong and brittle.

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20
Q

uses of aluminium alloys

A

lightweight alloys: aircraft
other aluminium alloys: armour plating on tanks and other military vehicles.

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21
Q

what are stainless steels alloys of?
what are their properties?

A

stainless steels:
- alloys of steel with chromium and nickel,
- hard, strong, the only steels which are resistant to corrosion.

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22
Q

what are stainless steels often used for
and why?

A
  • often used for reaction vessels,
  • because they are hard and strong, so withstand high pressures and temperatures,
  • and are resistant to corrosion, so withstand corrosive chemicals.
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23
Q

what do the properties of a polymer depend on?

A
  • the monomers they are made from,
  • the conditions of the reaction used to create it.
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24
Q

what is the difference between properties of thermosoftening and thermosetting polymers?

A

thermosoftening polymers melt when heated
whereas thermosetting polymers do not.

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25
Q

what is the difference between the structures of of thermosoftening and thermosetting polymers?

A

thermosoftening polymers: tangled up individual polymer chains, weak intermolecular forces between them, easily separated.

thermosetting polymer chains:strong covalent bonds between polymer chains, forming cross-links.

26
Q

what happens to a thermosoftening polymer when heated?

A
  • when heated, the weak intermolecular forces between polymer chains are broken,
  • so the polymer softens, melts.
27
Q

what happens to a thermosetting polymer when heated?

A
  • the strong covalent bonds which form cross-links between polymer chains mean that the chains cannot be separated,
  • thus the polymer does not soften/melt,
  • but can char at high enough temperatures.
28
Q

what is the most common type of glass
and what is it made from?

A

soda-lime glass
made with a heated mixture of sand, limestone and sodium carbonate

29
Q

what is borosilicate glass made of?
which of its properties is different from soda-lime glass’?

A

borosilicate glass:
- made of sand and boron trioxide,
- heats at higher temperatures than soda-lime glass.

30
Q

describe the arrangement of particles in glass and how it forms

A
  • as the heated raw materials cool down and solidify, the particles become set in place in a random arrangement.
31
Q

how are clay ceramics made?

A

by moulding wet clay then heating it in a furnace

32
Q

what is clay made of?

A

clay contains compounds of metals and non-metals

33
Q

describe the bonding in dry clay
(before being wet and fired)

A
  • clay contains compounds of metals and non-metals,
  • there is ionic bonding between metal and non-metal ions,
  • and some covalent bonding between non-metal atoms,
  • the ions and atoms are arranged in giant, layered structures.
34
Q

describe how bonding changes in wet clay as it is fired
and how this affects its properties

A
  • water molecules between the layers of ions and atoms are driven out,
  • so strong bonds form between the layers of the giant structure,
  • making the clay brittle,
  • because a sharp blow can distort the layers in its structure so that like-charged ions become adjacent and repel from each other, cracking the ceramic object.
35
Q

what is a composite usually made of?
what is the name of this process?

A

one material surrounding and binding together the fragments of another (reinforcement), forming a product with improved properties for a particular use.

36
Q

give 4 examples of composites

A

glass-ceramic composite
fibreglass
plywood
concrete

37
Q

give 2 materials that can bind to ceramics to make a composite

A

glass (glass-ceramic composites)
polymers

38
Q

why do farmers add fertiliser to soil?

A

to replace the nitrogen and nutrients lost from the soil when they take crops from it

39
Q

why do plants need nitrogen?

A

to make proteins for growth

40
Q

why can’t plants take in nitrogen gas from the air?

A

nitrogen gas in the air is insoluble in water
plants can only take in a soluble form of nitrogen

41
Q

what is ‘fixing’ nitrogen?

A

turning nitrogen gas in the air into nitrogen compounds that plants can absorb in solution

42
Q

what is the purpose of the Haber process?

A

to turn nitrogen gas into ammonia which can be turned into nitrogen that is soluble in water and absorbable by plants

43
Q

what are the raw materials for the Haber process?

A

nitrogen from the air
hydrogen, mainly from natural gas

44
Q

describe the steps of the Haber process

A
  • pass nitrogen and hydrogen over a CATALYST at HIGH TEMP (around 450 degrees C) and HIGH PRESSURE (around 200 atmospheres),
  • which produces AMMONIA,
  • some ammonia gas formed breaks down again into hydrogen and nitrogen because the reaction is REVERSIBLE,
  • remove ammonia by COOLING THE GASSES so that AMMONIA LIQUIFIES and can be separated from unreacted nitrogen gas and hydrogen gas,
  • RECYCLE UNREACTED HYDROGEN and NITROGEN GAS, recompress and reheat them, then return them to the reaction vessel so that they can react again to form ammonia.
45
Q

how is money spent to obtain the raw materials for the Haber process?

A
  • costs money to separate nitrogen from other gases in the air by fractional distillation for use,
  • costs money to produce the hydrogen gas by reaction of methane with steam.
46
Q

symbol equation for haber process

A

N2(g) +3H2(g) ⇌ 2NH3(g)

47
Q

how does increasing pressure affect the products of the Haber process? why?

A
  • the reaction is reversible so le chateliers principle applies:
  • reaction tries to counter change,
  • so point of equilibrium shifts to side with less pressure,
  • which here is to the right because there are less molecules of ammonia than there are reactants,
  • so more ammonia is produced.
48
Q

why is 200 atmospheres a compromised pressure for the haber process?

A
  • reduces costs of equipment and energy needed for higher pressures,
  • reasonable rate of reaction,
  • not maximum possible yield.
49
Q

why is 450 degrees C a compromised temperature for the haber process?

A
  • a lower temperature would give a higher yield of ammonia,
  • but a high temperature like this gives a reasonable rate of reaction due to more successful and energetic collisions of gas molecules,
  • and high temperature makes the catalyst more reactive.
50
Q

how would lower temperature give more ammonia in the Haber process?

A
  • reaction is reversible so le chatelier’s principle applies: reaction tries to counter change,
  • forward reaction is exothermic, increases temperature of surroundings,
  • so the product of the forward reaction (ammonia) is increased to counter the lowered temperature of the surroundings.
51
Q

is ammonia acidic or alkaline?

A

alkaline

52
Q

ammonia can be used to make nitric acid, which is then used to make what

A

nitric acid + ammonia -> ammonium nitrate (fertiliser)

53
Q

what are NPK fertilisers?

A

NPK fertilisers: formulations containing mixtures of nitrogen, potassium and phosphorus compounds that help plants grow healthily

54
Q

what can ammonia be used to produce

A

ammonia salts
and nitric acid

55
Q

how is phosphorus used in NPK fertilisers obtained?

A

from dug-up phosphate-containing rock
and treated with acid to make soluble fertiliser salts

56
Q

which acids is phosphate rock treated with? why?

A

nitric acid
sulfuric acid
because phosphate rock itself is insoluble, but when treated with these acids produces salts which are soluble therefore can be used as fertilisers

57
Q

how is potassium for NPK fertilisers obtained?

A

from potassium sulfate and potassium chloride dug from the ground

58
Q

does potassium need to be treated before use as fertiliser? why?

A

no
potassium compounds are already soluble in water so can be used directly as fertiliser (once separated from impurities)

59
Q

what does phosphate rock produce when treated with nitric acid?

A

ammonium nitrate

60
Q

what does phosphate rock produce when treated with sulfuric acid?

A

a single superphosphate

61
Q

what does phosphate rock produce when treated with phosphoric acid?

A

calcium phosphate

Chemistry AQA GCSE (8 decks)

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