Combustion – Class 11 | Chapter – 14 | Biology Short Notes Series PDF

Combustion: It is a chemical process or a reaction between Fuel (Hydrocarbon) and Oxygen. When fuel and oxygen react it releases the heat and light energy. Heat and light energy then result in the flame. So, the formula for the reaction is Hydrobcarbon + Oxygen = Heat energy. Combustion is used in car motors and rocket engines and many other machineries.

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Types of Combustion

  • Complete: When the reaction takes place in the presence of abundant Oxygen, the substances combine with Oxygen to their maximum extent. Such reactions have heat and light as a visible by-product.
  • Incomplete: These are defined as the reactions that occur in the absence of sufficient oxygen because of which substances are unable to burn completely. Such reactions leave soot in the container due to this process along with the formation of Carbon monoxide which is an air pollutant.
  • Rapid: Another type of combustion is Rapid Combustion. Rapid energy needs external heat energy for the reaction to occur. The combustion produces a large amount of heat and light energy and does so rapidly. The combustion will carry on as long as the fuel is available.
  • Spontaneous: As the name suggests it occurs spontaneously. This means that it requires no external energy for the combustion to start. It happens due to self-heating. A substance with low-ignition temperatures gets heated and this heat is unable to escape.
  • Explosive: It happens when the reaction occurs very rapidly. The reaction occurs when something ignites to produce heat, light and sound energy, The simple way to describe is it to call it an explosion. Some classic examples are firecrackers or blowing up of dynamite.

Important Points on Combustion

  • A non-cellular and uncontrolled process where energy is released in a single step by burning substances is called combustion. 

  • It is a physicochemical process where chemical steps occur simultaneously rather than step-wise. 

  • It liberates most of the energy as heat.

  • It also produces light and the temperature becomes very high during this process.

  • This process doesn’t include ATP generation.

  • Here, the substrate is directly oxidized in combustion without the production of any intermediates. 

  • It is a burning process that doesn’t require any enzyme.

Combustion Sources

1.  Fossil Fuels

Organic compounds can become rich in hydrocarbons when compacted underground for millions of years

  • The heat and pressure over time triggers a chemical transformation that results in the compaction of the organic matter
  • The resulting products of this process are fossil fuels (coal, oil and natural gas)
  • Because this geological process takes millions of years to occur, fossil fuels are a non-renewable energy source

2.  Biomass

An alternative to relying on fuels produced by geological processes is to manufacture fuels from biological processes

  • Living organisms produce hydrocarbons as part of their total biomass (either for use or as a waste product)
  • These hydrocarbons can be extracted and purified to produce an alternative fuel source (e.g. bioethanol and biodiesel)
  • Provided new raw materials are provided and waste products are removed, this source of energy is renewable

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By Team Learning Mantras