Fuels

Types of Fuels

  • Fuels are substances that release energy when they undergo a chemical reaction, usually combustion.
  • Fuels are often carbon compounds, notably hydrocarbons, derived from fossil fuels or biomass.
  • Hydrocarbons can be both saturated and unsaturated, depending on the types of carbon bonds present.

Combustion of Fuels

  • Combustion is a chemical reaction between a fuel and oxygen, producing energy in the form of heat and light.
  • Complete combustion happens in plenty of oxygen and it produces carbon dioxide and water.
  • Incomplete combustion occurs in insufficient oxygen, producing carbon monoxide and/or soot (carbon). This is damaging to human health and the environment.

Fossil Fuels

  • Fossil fuels are derived from the remains of ancient organisms, subject to heat and pressure over millions of years in the Earth’s crust.
  • They include coal, oil (petroleum), and natural gas.
  • Burning fossil fuels releases large amounts of carbon dioxide, contributing to global warming and climate change.

Renewable Fuels

  • Renewable fuels are sustainable alternatives to fossil fuels, derived from renewable resources.
  • Examples include biofuels such as ethanol (from fermentation of sugary plants) and biodiesel (from vegetable oils).
  • Biofuels also produce carbon dioxide but this is part of a short-term carbon cycle, whereas fossil fuels add to long-term carbon stocks.

Cracking of Hydrocarbons

  • Cracking is the process of breaking down large hydrocarbon molecules into smaller ones by the application of heat, a process important in the petrochemical industry.
  • This can produce smaller hydrocarbons for fuels or alkenes used in plastics manufacture.
  • Cracking can be either thermal (using heat) or catalytic (using a catalyst).

Fractional Distillation of Crude Oil

  • Crude oil, a mixture of hydrocarbons, is separated by fractional distillation.
  • Different fractions (parts) condense at different temperatures due to their different boiling points.
  • These fractions are used for different purposes, with lighter fractions like petrol and diesel used as fuels.

Remember, a firm understanding of these points will provide a good foundation for tackling the organic chemistry part of your revision. It’s also crucial to know that fuels, particularly fossil fuels, have a wide-ranging impact on our society and environment. Knowing their benefits, drawbacks, and alternatives will hold you in good stead for potential exam questions.