SC13b Corrosion

Question 1

metal + oxygen →

Answer 1

metal oxides

Question 2

how fast does a very reactive metal oxidise?

Answer 2

rapidly when freshly cut

Question 3

what may happen when metals oxidise? and why?

Answer 3

form a layer of tarnish which stops oxygen reaching the rest of the metal, prevent further oxidation

Question 4

when does corrosion happen?

Answer 4

when a metal continues to oxidise and becomes weaker over time

Question 5

rusting?

Answer 5

corrosion of iron

Question 6

iron + oxygen + water →

Answer 6

hydrated iron(III) oxide (rust)

Question 7

why is the iron made weaker when rusting?

Answer 7

rust flakes off which exposes the iron underneath to more oxygen and water so the metal continues to rust

Question 8

how can rusting be prevented?

Answer 8

~keeping air away - storing the metal in an unreactive atmosphere of nitrogen or argon
~keeping water away - storing metal with a desiccant powder that absorbs water vapour or coating with plastic, oiling, greasing
~sacrificial protection - more reactive metal placed on iron so it oxidises instead of the iron