chemistry C1 (4)

How is crude oil formed?

• about 150 million years ago the oceans were inhabited by tiny sea creatures when they died they fell to the bottom of the sea they became buried under sediment the bodies of the tiny sea creatures decayed the temperature and pressure slowly increased, they were changed into oil natural gas is usually found with the crude oil
• crude oil is obtained from under the sea by drilling through the layers of rock
• a pipe is fed down into the layer of oil, and the oil rises up the pipe due to pressure
• the oil is transported to a nearby refinery by pipeline, or by oil tanker to refineries all over the world
• accidents can happen at sea and oil can be spilled
• the crude oil that escapes floats on top of the sea forming an oil slick
• this can have disastrous effects on wildlife
• soapless detergents can be used to clean up the mess
• the detergent breaks up the oil slick, then the oil is spread out by the action of waves

How do we get fuels from crude oil?

• crude oil, natural gas and coal are fossil fuels
• fossil fuels are very precious resources because they are non-renewable
• as well as sources of energy, we can make lots of organic chemicals from them, needed to make products such as polymers, paints, detergents, cosmetics and some medicines

What is crude oil?

• crud oil is a complex mixture of a very large number of compounds
• most of the compounds in crude oil are made up of carbon and hydrogen atoms
• these compounds are celled hydrocarbons
• crude oil also contains small amounts of other chemicals such as sulphur
• crude oil, whilst hugely valuable as a resource, is useless as a mixture and must be sent to an oil refinery to be separated
• crude oil from different parts of the world or even from different depths in the same oil field, contains different mixture of hydrocarbons
• this is why they vary from light coloured volatile liquids to thick, dark oils

Alkanes

• most of the hydrocarbons in crude oil belong to a homologous series of compounds called alkanes
• the name of all alkanes ends in -ane
• the general formula is CnH2n+2
• the term saturated means that the molecule has the maximum number of bonds it can therefore no more atoms can be added

How is crude oil separated?

• in the oil refinery the many hydrocarbons in crude oil are separated in to fractions, each of which contains molecules with a similar number of carbon atoms
• the hydrocarbons in crude oil have different boiling points, according to the number of carbon atoms in the molecules
• fractional distillation is a separation process that uses the difference in boiling point to separate the hydrocarbons into fractions
• the crude oil is heated until it vaporises and the hot vapour is fed in near the bottom of the fractionating column
• the column is hot at the bottom and cool at the top
• the vapours rise up the…