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EdExcel GCSE Chemistry > Transition Metals, Alloys And Corrosion - Topic 5 > Flashcards

Transition Metals, Alloys And Corrosion - Topic 5 Flashcards

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1
Q

What are most metals?

A
  • most metals are transition metals
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2
Q

Physical properties of transition metals:

A
  • high mp and bp
  • formation of coloured compounds
  • catalytic activity of the metals and their compounds as exemplified by iron
  • ductile
  • malleable
  • strong, durable
  • shiny
  • dense
  • conducts electricity and heat
  • solid at RTP
  • can form more than 1 type of ion
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3
Q

What does a catalyst do?

A
  • transition metals are good catalysts
  • a catalyst is a substance that increases the rate of reaction by providing the reaction with an alternate reaction pathway that has a lower activation energy without being chemically changed or used up
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4
Q

Colour of copper compound:

A

blue

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5
Q

Colour of iron(II) compound:

A

pale green

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6
Q

Colour of iron(III) compound:

A

orange/brown

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7
Q

Colour of nickel compound:

A

green

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8
Q

Colour of chromium compound:

A

dark blue/green

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9
Q

Colour of cobalt compound:

A

pink - when it absorbs water

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10
Q

How could you prove that all the elements in the transition block are metals and not non-metals?

A
  • test conductivity of electricity - lump of elements can complete a circuit and light the bulb
  • metals will conduct electricity and non-metals won’t conduct electricity
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11
Q

Why is FeCl2 called iron(II) chloride and FeCl3 is called iron(III) chloride?

A

Roman numerals give charge of transition metals

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12
Q

Transition metal:

A

a metal found between Group 2 and 3 of the periodic table

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13
Q

What does the oxidation of metals result in?

A

oxidation of metals results in corrosion

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14
Q

Corrosion:

A
  • destruction of materials by chemical reactions with substances in the environment
  • e.g. iron rusts when exposed to water and oxygen
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15
Q

Example of corrosion:

A
  • rusting - both air and water are necessary for iron to rust
  • i.e. oxidation - gain of oxygen results in corrosion
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16
Q

How rusting of iron can be prevented:

A
  • exclusion of oxygen
  • exclusion of water
  • sacrificial protection
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17
Q

Methods of preventing the rusting of iron:

A
  • painting the iron surface
  • galvanising
  • sacrificial protection
  • stainless steel
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18
Q

How does painting the iron surface prevent iron from rusting?

A
  • applying oil and grease, covering in plastic
  • barrier method - stops O₂ and H₂O reaching iron and reacting with it
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19
Q

Potential problem of painting the iron surface to prevent the iron from rusting:

A
  • cover the iron
  • however, when the barrier is broken the iron will rust
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20
Q

Examples of painting the iron surface to prevent the iron from rusting:

A
  • bicycle chains (oil)
  • bicycle brake cables (plastic)
  • bridges (paint)
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21
Q

How does galvanising the iron prevent iron from rusting?

A
  • covering steel with zinc - still works even if zinc is scratched away at some places
  • zinc replaced once is is worn down
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22
Q

Potential problems of using galvanising to prevent the iron from rusting:

A
  • need to keep checking if there is enough zinc left on the iron
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23
Q

Examples of using galvanising to prevent the iron from rusting:

A

dust bin and some nails

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24
Q

How does sacrificial protection work to protect iron from rusting?

A
  • where the metal you want to be protected from rusting is galvanised with a more reactive metal, which will rust first and prevent water and oxygen reaching the layer underneath
  • e.g. zinc used to iron
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25
Q

Potential problems with using sacrificial protection to prevent iron from rusting:

A
  • more reactive metal can be chipped and iron will still not rust
  • need to keep checking if there is enough zinc left on the iron
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26
Q

Examples of using sacrificial protection to prevent iron from rusting:

A
  • ships
  • underground pipes
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27
Q

How is stainless steel used to prevent iron from rusting?

A
  • the chromium in stainless steel reacts with oxygen in the air to produce a protective chromium oxide layer across the surface
  • acts as a protective barrier
28
Q

Potential problems with using stainless steel to prevent iron from rusting:

A

more expensive

29
Q

Examples of using stainless steel to prevent iron from rusting:

A

cutlery

30
Q

What can electroplating be used to do?

A

can be used to improve the appearance and/or the resistance to corrosion of metal objects

31
Q

How can a metal object be covered with a coating of another metal?

A
  • if an iron object is completely covered with a coating of another metal the the iron will not rust - can be done by plating the object
  • often the metal coating can improve the appearance of the iron e.g. chromium plating
32
Q

Electroplating:

A

the process of coating a metal with a thin layer of another metal by electrolysis to improve the metal’s corrosion resistance or to improve the metal’s appearance

33
Q

Example of electroplating:

A
  • chromium plating covers the iron object with a thin layer of chromium
  • this stops the iron from rusting and gives the object a very shiny appearance
34
Q

How does electroplating work?

A
  • Electroplating acts as a barrier in order to exclude oxygen and water
  • Also improves appearance as you can electroplate a metal with an unreactive metal such as gold that is more attractive and will not corrode
  • The object to be plated is made the cathode (i.e. is given a negative charge) and dipped into a solution containing ions of the desired plating metal
35
Q

How does copper plating work?

A
  1. Connect the object to be plated to the negative terminal of a power supply using a wire and a crocodile clip
  2. Use a wire to connect a strip of copper to the positive terminal
  3. Place both objects into a solution of copper sulphate and turn the power supply on
  4. A lower voltage and rotation of the iron object usually gives the best results
36
Q

Diagram of copper plating:

A
37
Q

What is the solution used in copper plating?

A

copper sulphate

38
Q

What object is the cathode in copper plating?

A

the object being plated

39
Q

Write a half-equation for the reaction at the cathode in copper plating. What type of reaction is this?

A
  • Cu²⁺ + 2e⁻ ——> Cu
  • reduction
40
Q

What object is the anode in copper plating?

A

impure copper

41
Q

Write a half-equation for the reaction at the anode. What type of reaction is this?

A
  • Cu ——> Cu²⁺ + 2e⁻
  • oxidation
42
Q

Alloy:

A
  • a mixture of metals containing 2 or more metals together
  • process is carried out to give the material greater strength, greater resistant to corrosion or a better appearance
43
Q

What metals are mixed with other metals and why?

A

pure copper, gold, iron and aluminium are too soft for many uses and so are mixed with small amounts of similar metals to make harder alloys for everyday use

44
Q

What are most metals in every day use?

A

most metals in every day use are alloys

45
Q

Why are allows harder than pure metals?

A
  • this works because in a pure metal, all the + metal ions are the same size and in a regular arrangement, allowing the layers to slide over each other relatively easily when a force is applied → makes the metal soft and malleable
  • in an alloy, you have + ions of different metals, which have different sized ions
  • this disrupts the regular structure and prevents the ions being able to slide as easily, leaving a much harder, stronger metal
46
Q

What is steel an alloy of?

A
  • iron and small amount of carbon
  • other metals can be added to give it different properties
  • e.g. copper and nickel can be added to make stainless steel - doesn’t rust
47
Q

Why is iron alloyed with other metals to produce alloy steels

A
  • Some steels contain other metals
  • Alloys can be designed to specific uses
48
Q

Why is iron alloyed to form mild steel?

A
  • made up of 99.5% iron and 1% carbon
  • mild steel is easily worked, malleable and strong as it has lost most brittleness
  • it is used in car bodies, machinery and sheeting
49
Q

Why is iron alloyed to form hard steel?

A
  • made up of 99% iron and 1% carbon
  • hard steel is tough and brittle
  • it is used in power shovels ~~and cutting tools~~
50
Q

Why is iron alloyed to form stainless steel?

A
  • made up of iron, chromium and nickel
  • stainless steel is tough and resistant to corrosion
  • it is used in chemical plants and cutlery
51
Q

Why is iron alloyed to form tungsten steel?

A
  • made up of iron and tungsten
  • tungsten steel is tough and hard - even at high temperatures
  • it is used in micro-drills
52
Q

Properties of aluminium:

A
  • low-density
  • malleable
  • low reactivity
  • low toxicity
53
Q

Uses of aluminium:

A
  • aircraft parts
  • cooking foil - malleable, low toxicity, low reactivity
54
Q

Properties of copper:

A

good conductor

55
Q

Uses of copper:

A

electrical cables

56
Q

Properties of gold:

A
  • good resistance to corrosion
  • good electrical conductor
  • attractive appearance
57
Q

Uses of gold:

A
  • used in jewellery
  • electrical contacts - doesn’t corrode + food electrical conductor
58
Q

What is brass an alloy of?

A

an alloy of copper and zinc

59
Q

Properties of brass:

A
  • hard
    • copper made harder by addition of zinc
    • in brass the layers of the copper atoms cannot slide over each other as easily as larger zinc atoms get in the way
  • resistant to corrosion
  • looks good
  • strong and long lasting
60
Q

Uses of brass:

A
  • musical instruments - looks good and doesn’t corrode
  • door handles - doesn’t corrode
  • pins for electrical plugs - strong and hard wearing
61
Q

What is magnalium an alloy of?

A

magnesium and aluminium

62
Q

Properties of magnalium:

A
  • strong
  • resistant to corrosion
  • low density
  • flammable
63
Q

Uses of magnalium:

A
  • cars
  • aircrafts
64
Q

What is electrum an alloy of?

A

silver and gold

65
Q

Uses of electrum:

A
  • coins
  • jewellery
66
Q

What is bronze an alloy of?

A

copper and tin

67
Q

Properties of bronze:

A
  • harder than copper
  • less malleable

EdExcel GCSE Chemistry (29 decks)

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