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.