3.3.5 - iron, steel and other metals

Question 1

what is rusting

Answer 1

a chemical process by which iron is oxidised to form rust

Question 2

what is the chemical name for rust

Answer 2

hydrated iron(III) oxide

Question 3

what 2 substances does rusting require

Answer 3

oxygen and water

Question 4

rusting happens in 2 stages :

Answer 4

1. iron is oxidised by oxygen to form iron(III) oxide
2. iron(III) oxide is hydrated by water

Question 5

what methods can be used to prevent rusting?

Answer 5

• using barriers
• sacrificial protection
• galvanising

Question 6

barrier method to prevent rusting:

Answer 6

• coat the iron in paint, oil, grease or plastic to prevent the iron coming into contact with oxygen or water
• as soon as the coating breaks, rusting happens

Question 7

sacrificial protection to prevent rusting:

Answer 7

• attach a more reactive metal to the iron
• the works by displacing the iron from rust as soon as the rust forms
• downside is block of more reactive metal has to be replaced often

Question 8

galvanising to prevent rusting:

Answer 8

• involves coating the iron in zinc
• coating prevents oxygen and water coming into contact
• if there is a crack in the coating, zinc is more reactive than iron