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What you need to know
Reflections and Exam tips
Crude oil is made from ancient biomass found in rocks. Crude oil is made up from a mixture of different hydrocarbons.
Properties of Alkanes
The hydrocarbons in crude oil are separated using fractional distillation due to their different boiling points.
Outline steps of fractional distillation
Each fraction contains molecules with a similar number of carbon atoms.
Combustion of fuels
Most fuels, including coal and oil, contain carbon and hydrogen but may also contain some sulphur.
The gases released into the atmosphere when a fuel burns may include carbon dioxide, water (vapour), carbon monoxide, sulfur dioxide and oxides of nitrogen.
Solid particles (particulates) may also be released.
Complete combustion (plenty oxygen): Hydrocarbon + oxygen ——> carbon dioxide + water
Incomplete combustion (less oxygen): hydrocarbon + oxygen ——> carbon (soot) + carbon monoxide + water
Carbon monoxide is an odourless, colourless gas that replaces oxygen in red blood cells so that your cells receive less oxygen, which can be harmful.
Solid particles cause global dimming. Carbon particles (soot) are thought to be responsible for a reduction in sunlight reaching the Earth called global dimming. Rain clouds form around the carbon particles and these clouds reflect the Sun’s rays back into space.
Carbon dioxide causes global warming. Carbon dioxide is a greenhouse gas and with CO2 levels increasing in the atmosphere, Earth's average temperatures are also increasing (global warming as more heat is trapped on Earth). This could lead to climate change which might include flooding due to melting polar ice-caps.
Sulphur can be removed from fuels before they are burned.
Sulphur dioxide can be removed from the waste gases after combustion using scrubbers.
Catalytic converters in the exhausts of vehicles reduce the release of nitrogen oxides.
Biofuels, including biodiesel and ethanol, are produced from plant material, e.g rapeseed oil.
Ethanol which is an alcohol produced by fermenting plants can be used instead of petrol in cars.
Hydrogen is easily made by electrolysis of water to be used as car fuel.
Describe how crude oil was formed
Explain why we describe crude oil as a mixture of compounds
Define the term hydrocarbon
Most compounds in crude oil are hydrocarbons
Alkanes are saturated hydrocarbons
Properties of hydrocarbons depend on the size of their molecules
Discuss the environmental impact of burning fuels?
How can using biofuels be beneficial to the environment?