topic 5 - transition metals, alloys and corrosion

Question 1

where are transition metals found

Answer 1

in the middle of the periodic table

Question 2

typical properties of transition metals (4)

Answer 2

• high melting point (apart from mercury)
• high density
• make good catalysts (eg iron is used in the haber process)
• form colourful compounds

Question 3

what colour compounds do Fe^2+ ions form

Answer 3

light green

Question 4

what colour compounds do Cu^2+ ions form

Answer 4

blue

Question 5

what colour compounds do Fe^3+ ions form

Answer 5

orange/brown

Question 6

alloy

Answer 6

a mixture of metals / the addition of another element to a metal

Question 7

why are alloys stronger

Answer 7

they contain different elements with different sized atoms making it difficult for layer to slide over each other

Question 8

steels

Answer 8

alloys of iron

used more often than pure iron

Question 9

how is steel made

Answer 9

small amount of carbon are added to iron

other metals are added to make alloy steels

Question 10

general differences steel vs iron (2)

Answer 10

• steels are harder than iron

- iron is more likely to rust than steel

Question 11

3 types of steel

Answer 11

low carbon steel
high carbon steel
stainless steel

Question 12

low carbon steel (make-up and properties)

Answer 12

0.1-0.3% carbon

malleable

Question 13

high carbon steel (make-up and properties)

Answer 13

0.22-2.5% carbon

very strong, brittle and inflexible

Question 14

stainless steel (properties)

Answer 14

corrosion resistant

strong

Question 15

copper alloy examples

Answer 15

bronze

brass

Question 16

bronze (makeup)

Answer 16

copper + tin = bronze

Question 17

bronze (properties and uses)

Answer 17

bronze is much harder than copper

made into medals, statues and decorative ornaments

Question 18

brass (makeup)

Answer 18

copper + zinc = brass

Question 19

brass (properties and uses)

Answer 19

brass is more malleable than bronze

used in situations where less friction is needed such as water taps and door fittings

Question 20

gold alloys (makeup and uses)

Answer 20

zinc, copper and silver used to strengthen the very soft and malleable gold
used to make jewellery

Question 21

aluminium alloy example

Answer 21

magnalium

Question 22

aluminium alloys (properties and uses)

Answer 22

low density and stronger than regular aluminium

used to make aircraft

Question 23

magnalium (makeup)

Answer 23

aluminium + magnesium = magnalium

Question 24

low magnesium content magnalium (properties and uses)

Answer 24

light strong and corrodes less easily than pure aluminium

used for cars and aeroplanes

Question 25

high magnesium content magnalium (properties and uses)

Answer 25

more reactive, burns brightly and is more stable than magnesium
used for fireworks

Question 26

corrosion

Answer 26

a process where something is slowly damaged or destroyed by a chemical process

Question 27

rusting

Answer 27

the corrosion of iron

Question 28

what is corrosion (reaction)

Answer 28

corrosion is caused by redox reactions
metals corrode in the presence of water and oxygen
metal is oxidised
oxygen is reduced

Question 29

how to prevent rusting (what are you blocking)

Answer 29

coating iron with a barrier to keep out oxygen or water or both

Question 30

how can you prevent rusting (techniques)

Answer 30

painting
oiling or greasing (especially on moving parts)
sacrificial protection

Question 31

sacrificial protection

Answer 31

placing a more reactive metal with iron so it is corroded instead

Question 32

galvanisation

Answer 32

an example of sacrificial protection where a coat of zinc is placed on an iron object
often done to corrugated iron roofing

Question 33

electroplating

Answer 33

coating the surface of a metal with another metal using electrolysis

Question 34

what should the cathode, anode and electrolyte be in electroplating

Answer 34

cathode - the object to be electroplated
anode - bar of metal being used as plating
electrolyte - solution containing metal ions of the plating metal

Question 35

2 examples of when we use electroplating

Answer 35

we electroplate household items such as cutlery/cooking utensils to stop corrosion (protective metals used are unreactive and don’t corrode easily)

jewellery and decorative items may be electroplated gold or silver to make them look shiny

Question 36

what happens in terms of movement of ions in electroplating

Answer 36

metal ions from electrolyte move to the cathode, where they are reduced and the metal is deposited on the object
the anode keeps the metal ions ‘topped up’