Iron, Steel and Other Metals

Question 1

what is rusting?

Answer 1

rusting is the chemical process by which iron is oxidized to form rust

Question 2

what is the chemical name for rust?

Answer 2

hydrated iron(III) oxide

Question 3

rust word equation?

Answer 3

iron -> iron(III) oxide -> hydrated iron(III) oxide

Question 4

rust symbol equation?

Answer 4

Fe(s) -> Fe2O3(s) -> Fe2O3 xH2O(s)

Question 5

properties of iron?

Answer 5

• grey
• shiny
• malleable

Question 6

properties of hydrated iron(III) oxide?

Answer 6

• brown
• brittle
• dull

Question 7

what two substances does rust require?

Answer 7

• oxygen
• water

Question 8

what are the two stages of rusting?

Answer 8

1. iron is oxidized by oxygen to form iron(III) oxide - Fe has gained oxygen and it has also lost electrons to form Fe3+ ions, for both reasons it has been oxidised
2. iron(III) oxide is hydrated by water - the amount of water gained by the iron(III) oxide varies a lot

Question 9

what are the three methods that can prevent rusting?

Answer 9

• using barriers
• sacrificial protection
• galvanising

Question 10

how can rusting be prevented by using barriers?

Answer 10

• coating the iron in paint, oil, grease or plastic prevents the iron from coming into contact with oxygen or water (this only works as long as this coating is intact - as soon as it breaks rusting happens)
• you choose the coating material depending on the use for the iron - oil or grease for moving parts (e.g. bike chains), paint or plastic for larger more stationary objects (e.g. buckets)

Question 11

how can rusting be prevented using sacrificial protection?

Answer 11

• attach a block of a more reactive metal (e.g. magnesium) to the iron
• this works by displacing the iron from rust as soon as the rust forms
• the downside to this method is that the block of magnesium has to be replaced often

Question 12

what is the word equation for the magnesium rust displacement reaction?

Answer 12

magnesium + iron(III) oxide -> magnesium oxide + iron

Question 13

what is the symbol equation for the magnesium rust displacement reaction?

Answer 13

3Mg(s) + Fe2O3(s) -> 3MgO(s) + 2Fe(s)

Question 14

how can rusting be prevented using galvanising?

Answer 14

• this method specifically involves coating the iron in zinc
• coating prevents oxygen and water from coming in contact with the iron, but even if a crack appears, zinc is more reactive than iron so acts as sacrificial protection as well

Question 15

what is an alloy?

Answer 15

alloys are mixtures of a metal with one or more other elements, usually other metals or carbon

Question 16

commonly known alloys?

Answer 16

• steel (elements = iron + carbon)
• brass (elements = copper + zinc)
• bronze (elements = copper + tin)

Question 17

why are alloys harder than pure metals?

Answer 17

the different sized atoms/ions prevent the layers of metal ions sliding over each other - this means the alloy is less malleable

Question 18

iron - elements, use and reason?

Answer 18

elements = Fe
use = making steel
reason = steel is more useful than iron

Question 19

low-carbon steel - elements, use and reaction?

Answer 19

elements = Fe + 0.1% C
use = ships, cars, bridges etc.
reason = strong, but low-carbon so can be hammered into various shapes

Question 20

high-carbon steel - elements, use and reaction?

Answer 20

elements = Fe + 1% C
use = tools e.g. knives, screwdrivers
reason = high-carbon so less malleable and stiffer than low-carbon steel

Question 21

stainless steel - elements, use and reaction?

Answer 21

elements = Fe + 1% C + 10% Cr
use = cutlery, cooking utensils, kitchen sinks
reason = Cr forms oxide layer than resists corrosion, so stays shiny and clean

Question 22

copper - elements, use and reaction?

Answer 22

elements = Cu
use = wires, cooking pans, water pipes
reason = excellent conductor of electricity, excellent conductor of heat, unreactive and malleable

Question 23

aluminium - elements, use and reason?

Answer 23

elements = Al
use = aircraft bodies, power cables
reason = low density and high strength, low density and conducts