2020-04-08
Unit 1: Reactions of metals with oxygen
Terminology:
 Combustion: rapid chemical reaction with oxygen
that produces heat and light.
Topic 7: Reactions of metals
and non-metals with oxygen
Grade 9
Natural Sciences (Platinum pg. 89-98)

When a substance reacts with oxygen the reaction
is called oxidation. A new compound is formed,
called an oxide is formed.

Metal + oxygen
 Oxide: compound formed when a substance reacts
with oxygen
 Metal oxide: compound formed when a metal
reacts with oxygen.
Combustion of different metals
(page 90)
Metal oxide
Copper
Sodium (flame: Potassium (flame:
bright yellow)
purple/red)
Reaction of iron with oxygen

Zinc (flame: white
in pure O2)
Reaction of magnesium with oxygen
When iron is burnt in the air, the reaction forms
iron oxide. During combustion, Fe2O3 and Fe3O4
are formed.

Magnesium burnt in the air, magnesium oxide is formed.

Word equation: Magnesium + oxygen

Balanced: 2Mg+O2
Magnesium oxide
Gold flame

Word equation: iron + oxygen

Balanced equation: 4Fe+3O2
iron oxide
2MgO
2Fe2O3
White flame
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Activity

Complete activity 3 on page 92
The reactions of metals with oxygen
Elements
Symbol
Flame
colour
Name of
product
Colour &
nature of
product
Solubility
of product
in water
Colour of
lithmus in
solution
Sodium
Potassium
Calcium
Zinc
Copper
Magnesium
Iron
Unit 2: Rusting

Rusting is a form of corrosion.
(Corrosion is the process where a
metal is weakened or damaged due
to chemical reactions).

Rusting is the chemical reaction of
iron and oxygen with the presence of
water in the environment.

Rusting occurs when iron reacts with oxygen
in the presence of water/moisture. Water is
a vital element needed for the rusting
process to take place.

Part of the compound formed = iron oxide
(Fe2O3).

Why would a bicycle rust faster in Cape
Town than Johannesburg?
Formation of rust
All metals don’t corrode at the same
extent. Some metals that corrode
faster are more reactive.
Eg. Sodium, it corrodes so quickly it has
to be stored in oil.


Least reactive metals like platinum and
gold, do not corrode even after many
years!
Ways to prevent rusting
Galvanize: iron is coated with
a thin layer of a more reactive
metal. Eg: Zinc
(page 95)
Electroplating: Electrolysis
reaction a thin layer of a less
reactive metal to protect the
reactive metal.
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Ways to prevent rusting
Activity
Complete activity 5 on page 95

Painting: paint prevents iron
from coming into contact with
water and oxygen in the air. If
paint scratched – rust forms.
Oil: oiling prevents rust by
repelling water. Oil and water
do not mix, and the water
won’t come into contact with
the iron.
Unit 3: Reactions of non-metals with
oxygen
Reactions of carbon with oxygen

Colourless gas carbon dioxide is formed. Carbon
dioxide can’t be seen or smelt – to observe CO2 we
use clear lime water to see the effect.

Balanced Eq. C+O2
Reactions of sulfur with oxygen

Blue bright flame is seen and a colourless gas
sulfur dioxide is formed. Toxic, strong smell, it is
released when a volcano erupts.

Balanced eq: S + O2
CO2
Activity

Topic 7 revision on page 98
SO2
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The reactions of non-metals with oxygen
Elements
Symbol
Flame
colour
Name of
product
Colour &
nature of
product
Solubility Colour of
of
lithmus in
product in solution
water
Carbon
Sulphur
Phosphorus
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