chemistry

> crude oil is a mixture of many different compounds

> many of the compounds in crude oil are hydrocarbons- they contain only hydrogen and carbon

> alkanes are saturated hydrocarbons. They contain as much hydrogen as possible in their molecules

fuels from crude oil

> we seperate crude oil using fractional distilation

> properties of each fraction depend on the size of the hydrocarbon molecules

> lighter fractions make better fuels

fractional distilation

> when we burn hydrocarbon fuels in plenty of air they produce carbon dioxide and water

> impurities in fuels may produce other substances which may be poisonous and/or which may cause pollution

> changing the conditions in which we burn fuels may change the products that are made

burning fuels

> burning fuels releases substances that spread throughout the atmosphere

> some of these substances dissolve in droplets of water in the air, which then fall as acid rain

> carbon dioxide produced from burning fuels is a greenhouse gas. It reduces the rate at which energy is lost from the surface of the Earth by radiation

> the pollution produced by burning fuels may be reduced by treating the products of combustion. This can remove substances like nitrogen oxides, sulfur dioxide and carbon monoxide

cleaner fuels