Fuels and Combustion – GCSE Chemistry (Triple) CCEA Revision

Understanding Fuels and Combustion

Fuels are substances that can be used to generate energy, typically through the process of combustion.
They can be in solid, liquid or gas form. Examples include coal (solid), petrol (liquid), and natural gas (gas).
Fuels can be classified into two main categories: renewable (can be replaced within a human lifetime, e.g., biofuels, wood) and non-renewable (cannot be quickly replaced, e.g., oil, coal, natural gas).

Combustion is a type of exothermic reaction where a fuel reacts with oxygen, releasing heat energy.
It’s generally represented by the equation: Fuel + Oxygen → Carbon Dioxide + Water
However, in reality, insufficient oxygen may result in incomplete combustion, producing carbon (soot) or carbon monoxide, both of which can be harmful.
When fuels such as coal and petrol burn, they release carbon dioxide into the atmosphere, contributing to global warming, a major environmental issue.

Ideally, a good fuel must be easily available, cheap, efficient, easy to store, safe to transport, and have a high calorific value (energy content per unit mass).
It should burn cleanly, without producing much smoke or undesirable byproducts.
Natural gas, hydrogen, and alcohol can be viewed as clean fuels, as they burn almost completely with oxygen to produce water and minimal quantities of carbon dioxide.

The combustion of fossil fuels (coal, oil, and natural gas) is a major source of energy in the industrialised world.
However, it also contributes significantly to air pollution and the greenhouse effect, owing to the release of carbon dioxide and other pollutants.
Additional pollutants include sulphur dioxide, which comes from impurities in the fuel and can cause acid rain, and nitrogen oxides, which contribute to smog.

Given the environmental issues associated with fossil fuels, there’s a growing interest in using renewable energy sources such as wind, solar or hydroelectric power.
Biofuels, obtained from plant or animal sources, are another promising renewable fuel source. For example, biodiesel is made from vegetable oils or animal fats.
Hydrogen can be a clean fuel source; its combustion with oxygen produces water as a byproduct. However, safe storage and transportation of hydrogen are significant challenges.

Fuels should be used safely due to the risks of fire and explosion, and the production of harmful gases.
Carbon monoxide, a byproduct of incomplete combustion, is a poisonous gas that can be lethal in confined spaces.
Fire safety involves understanding the fire triangle - fuel, heat, and oxygen - removing any of these can put out a fire.