Combustion
Reactions
What is combustion?
• a very rapid reaction of a
substance with oxygen to
produce compounds called
oxides.
FUEL + OXYGEN  OXIDE + ENERGY
• commonly
referred to as
burning
• easily identified
by the production
of heat
(exothermic)
• type of synthesis
reaction
Requirements
• Three requirements for a combustion
reaction
Fuels
•Gaseous Fuels
•
•
Natural Gas/Methane - used for cooking, heating etc.
Acetylene - used in welding, cutting etc.
• Liquid Fuels
• Petrol - used for internal combustion engines etc.
• Paraffin/kerosene - used in heating appliances etc
• Alcohols - used widely but includes preservatives,
preparations, solvents etc.
• Oils - used for lubrication etc.
Fuels
• Solid Fuels
• Wood/paper/card.
• Plastics - most plastics will release toxic smoke
during combustion.
• Metals - some metals are flammable, although
usually very high temperatures are required.
• Foodstuffs - we actually 'burn' our food in order
to cook it.
The most common fuels
are hydrocarbons
Complete Combustion
• Complete combustion of a
hydrocarbon produces carbon
dioxide gas and water vapour.
Hydrocarbon + Oxygen  Carbon dioxide + Water
methane + oxygen  carbon dioxide + water
CH4 + 2 O2  CO2 + 2 H2O
Complete Combustion
• Complete combustions occurs
when:
• Sufficient oxygen is present
• Temperature is hot enough
Complete combustion is characterized by a
blue flame. The flame is hotter than the flame
of incomplete combustion.
Incomplete Combustion
• If insufficient oxygen is present,
hydrocarbons burn to produce
water vapour along with carbon
monoxide, carbon dioxide and/or
solid carbon.
2CH4 + 3 O2  2CO + 4 H2O
CH4 +
O2 
C + 2 H2O
Incomplete Combustion
• Incomplete combustion is
characterized by an orange or
“dirty” flame.
• Produces black “soot” and the
poisonous gas carbon monoxide
Time to Get to Work
• combustion animation
Page 140 #19-24
Page 141 #41, 43, 46, 47, 49