CombustionReactions

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

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