Chemistry of Combustion

Chemistry of Combustion

Introduction to Combustion

• Combustion is an exothermic reaction which involves the rapid combination of a substance (fuel) with oxygen.
• During combustion, energy is released in the form of light and heat.
• To initiate combustion, activation energy (the energy required to start a reaction) must be provided. This is typically obtained via a heat source such as a match or spark.

Complete and Incomplete Combustion

• Complete combustion occurs when there is plenty of oxygen present. This produces carbon dioxide and water.
• Incomplete combustion occurs when the supply of oxygen is limited. This produces carbon monoxide, soot (carbon particles) and water.
• Both carbon monoxide and soot are dangerous pollutants posing health and environmental risks.

Calculating Energies in Combustion Reactions

• Calorimetry is used to measure the heat change in a chemical reaction.
• The thermal or heat energy released during combustion can be determined by measuring the temperature change of a known mass of water.

Chemical Equations for Combustion

• Combustion reactions can be represented using chemical equations.
• Balance the equations considering the law of conservation of mass which says that matter cannot be created or erased.
• remember that oxygen (O2) and most hydrocarbon fuels exist as diatomic molecules in their natural state.

Fire Triangle

• For combustion or a fire to occur, three things are needed: fuel, oxygen and heat. This concept is often represented as the Fire Triangle.
• Taking away any one element will extinguish the fire. This forms the basis of fire-fighting methods.