1. Combustion Reactions

2. What is combustion?
a very rapid reaction of a substance with oxygen to produce compounds called oxides.
FUEL + OXYGEN  OXIDE + ENERGY

3. commonly referred to as burning
easily identified by the production of heat (exothermic)
type of synthesis reaction

4. Requirements
Three requirements for a combustion reaction

5. Fuels Gaseous Fuels Liquid 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.

6. Fuels Solid Fuels The most common fuels are hydrocarbons
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

7. Complete Combustion
Complete combustion of a hydrocarbon produces carbon dioxide gas and water vapour.
Hydrocarbon + Oxygen  Carbon dioxide + Water
methane + oxygen  carbon dioxide + water
CH O2  CO H2O

8. 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.

9. Incomplete Combustion
If insufficient oxygen is present, hydrocarbons burn to produce water vapour along with carbon monoxide, carbon dioxide and/or solid carbon.
2CH O2  2CO + 4 H2O
CH O2  C H2O

10. Incomplete Combustion
Incomplete combustion is characterized by an orange or “dirty” flame.
Produces black “soot” and the poisonous gas carbon monoxide

11. Time to Get to Work combustion animation Page 140 #19-24