Summary Grade 9: NS: Revision Notes

Reactions of metals and non-metals with oxygen
Reactions of metals with oxygen
Metal + oxygen  metal oxide
Reactants  products

Reaction of magnesium with oxygen
 Forms the product magnesium oxide
 2Mg + O2  2MgO
 Produces a bright white light which can damage your eyes when burning. The end product
is a white powder

Reaction of iron with oxygen
 A metal like iron will gradually react with oxygen in the atmosphere to form a metal oxide
e.g. iron oxide
 Iron reacts easily with oxygen to form rust
 Water and oxygen are required for iron to rust
 2 types of iron oxide form:
• 4Fe + 3O2  2Fe2O3 = Rust
• 3Fe + 2O2  Fe3O4 = Magnetite

Rusting
 Occurs on the surface of iron
 Iron is in contact with oxygen and moisture/water
 Rusting is a type of corrosion where metal is damaged or weakened
 Reactive metals corrode quicker (group 1)
 Non-reactive metals will not corrode even after many years (closer to zig-zag line on the
periodic table) such as gold or platinum
Preventing Rust
Galvanise
 covering with another metal that does not rust so easily
Electroplating or chrome plating
 process of electrolysis
 deposits thin layer of chromium (more reactive metal)
 forms shiny, attractive surfaces
Paint
 prevents metal contact with water/moisture and oxygen
Bars that protect ships (sacrificial anodes)
 connecting/adding more reactive metal bars (magnesium alloys or zinc)
 bars corrode first
Oiling
 oil repels water (oil is hydrophobic)

Reactions of non-metals with oxygen
Non-metal + oxygen  non-metal oxide
Reactants  product
Carbon + oxygen  carbon dioxide (C + O2  CO2)