C1.4 Crude Oil And Fuels

Mind Map by killthemoment, updated more than 1 year ago
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GCSE Chemistry (C1) Mind Map on C1.4 Crude Oil And Fuels, created by killthemoment on 07/21/2014.

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C1.4 Crude Oil And Fuels
1 C1.4.1 Crude Oil
1.1 Crude oil is a mixture of a very large number of compounds.
1.1.1 A mixture consists of two or more elements or compounds not chemically combined together. The chemical properties of each substance in the mixture are unchanged. It is possible to separate the substances in a mixture by physical methods including distillation. Most of the compounds in crude oil consist of molecules made up of hydrogen and carbon atoms only (hydrocarbons). Most of these are saturated hydrocarbons called alkanes, which have the general formula CnH2n+2. Saturated hydrocarbons have only single bonds. This makes them relatively unreactive, apart from burning or combustion, which is their reaction with oxygen in the air.
2 C1.4.2 Hydrocarbons
2.1 The many hydrocarbons in crude oil may be separated into fractions, each of which contains molecules with a similar number of carbon atoms.
2.1.1 The crude oil is evaporated and its vapours condense at different temperatures in the fractionating column. The column is hot at the bottom and cool at the top; substances with high boiling points condense at the bottom and substances with lower boiling points condense on the way to the top. This is known as fractional distillation. Properties of hydrocarbons depend on the size of their molecules; influencing how hydrocarbons are used as fuels. Smaller molecules have lower boiling points, lower viscosity (flow more easily) and higher flammability (ignite more easily).
3 C1.4.3 Hydrocarbon Fuels
3.1 Most fuels, including coal, contain carbon and/or hydrogen and may also contain some sulfur. Fuels burn when they react with oxygen in the air. If there is plenty of air, complete combustion happens. Coal is mostly carbon. During complete combustion, carbon is oxidised. The gases released into the atmosphere when a fuel burns may include carbon dioxide and water vapour.
3.1.1 If there is insufficient air, incomplete combustion happens. Hydrogen is still oxidised to water, but carbon monoxide forms instead of carbon dioxide; a toxic gas, so adequate ventilation is important when burning fuels. Solid particles (particulates) are also released. These contain carbon and are seen as soot or smoke. Particulates cause global dimming; reducing the amount of sunlight reaching the Earth’s surface. The combustion of hydrocarbon fuels releases energy. During combustion the carbon and hydrogen in the fuels are oxidised. Sulfur dioxide and oxides of nitrogen cause acid rain, carbon dioxide causes global warming, and solid particles cause global dimming. Sulfur can be removed from fuels before they are burned; in vehicles. Sulfur dioxide can be removed from the waste gases after combustion; in power stations. Biofuels, including biodiesel and ethanol, are produced from plant material. There are economic, ethical and environmental issues surrounding their use: agricultural land is used which may cause food shortages or increases in the price of food; more people are needed to produce biofuels than petrol and diesel; increased income for farmers; lower fuel prices; biodiesel naturally contains little sulfur and they may be said to be carbon neutral however, while biofuels produce less carbon dioxide, overall, they are not carbon neutral - because fossil fuels are used in their production, for example in making fertilisers for the growing plants.
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