What is the topic for today?
Fuels
Combustion and
Incomplete Combustion
Learning Objectives:
1.Know word (and symbol) equations for
complete combustion and the limewater
test for CO2.
2.Describe the differences between
complete and incomplete combustion.
3.Write word equation for complete and
incomplete combustion.
1. Combustion, fuels and hydrocarbons
When a substance burns,
it is said to combust.
Combustion is a rapid
reaction between a
substance and oxygen
that releases heat and
light energy.
A fuel is a substance that reacts with oxygen
(combusts) to release useful energy.
Many fractions obtained from crude oil are used as fuels
because they contain hydrocarbons that burn easily and
release a large amount of useful energy.
2. Complete combustion of hydrocarbons
If a flame has A LOT of oxygen, the fuel will burn
completely.
Complete combustion of a
hydrocarbon (in this case,
natural gas) releases the
most energy (hottest flame).
What are the products of the complete combustion of a
hydrocarbon?
hydrocarbon
+
carbon
oxygen 
dioxide
+
water
3. Oxidation
• Combustion is a form of oxidation.
• Oxidation is a chemical reaction where
oxygen is added.
4. Complete combustion of propane
Propane is a hydrocarbon used in camping gas. What is the
equation for its combustion?
+
propane
C3H8
+
oxygen 
O2

carbon
dioxide
CO2
+ water
+
H2O
Extra
Challenge:
Balance it!
C3H8
+
5O2

3CO2
+
4H2O
Write the word and symbol equation for the burning of
a) methane
b) ethane
c) butane
5. Test for CO2
• What is the test for CO2?
• Bubble the gas through limewater.
Limewater turns cloudy in the presence of
CO2.
6. Incomplete combustion of hydrocarbons
If there is a shortage of air (oxygen), incomplete
combustion of hydrocarbons takes place.
Instead of producing just
carbon dioxide and water,
incomplete combustion also
produces carbon monoxide
and/or carbon (soot).
It also releases less energy
than complete combustion.
What is the chemical equation for incomplete
combustion?
7. Word equation
hydrocarbon + oxygen 
carbon dioxide + carbon monoxide + carbon + water
8. Pollution
• Combustion causes pollution.
• Pollutant: a substance which causes
harm to organisms or the environment.
• Pollutants from combustion:
a)
b)
c)
d)
e)
Carbon dioxide
Carbon monoxide
Carbon soot
Sulfur dioxide
Nitrogen oxides
9. Global Warming
• Watch the video and answer the following
questions.
• What is global warming?
• What causes it?
• Describe the greenhouse effect.
• Global warming is the increasing of the
average worldwide temperature.
• It is caused by greenhouse gases such
as carbon dioxide, methane, and water
vapour.
• The greenhouse effect is the heating of
the earth caused by greenhouse gases
trapping heat from the sun near the earth’s
surface.
10. Acid rain
• Acid rain is rain that has a lower pH than
normal (lower than 5.5)
• Acid rain is caused by pollutants such as
sulphur dioxide and nitrogen oxides from
combustion of fuels.
Effects
a)Organisms in lakes can die
b)Trees are damaged
c)Buildings/rocks are corroded
11. Pollutants Summary
Pollutant
Cause
Carbon dioxide
All combustion
Carbon
monoxide
Incomplete
combustion
Carbon (soot)
Incomplete
combustion
Sulphur dioxide
Combustion of fossil
fuels with sulphur
impurities
Combustion of fuels
inside car engines
Nitrogen oxides
Effect
Global warming, makes
ocean more acidic
Poisonous, reduces
blood’s ability to carry
oxygen
Breathing problems
Global dimming
Acid rain (sulphuric
acid) and breathing
problems
Acid rain (nitric acid)