Tuesday, 18 February 2014

GCES chemistry - unit 1 - crude oil

Crude Oil

Crude oil is made up of remains of sea creatures, decomposing under the sea bed with no exposure to air and is deeply buried in rock under the sea. In the sea, pipelines supply crude oil to oil rigs which is then pumped into oil tankers which take it to be processed.

Crude oil is a thick, black and stickler liquid and is a mixture of lots of different compounds. Because it is a mixture, it is easily separated because the compounds are not chemically bonded.

Separating these compounds - FRACTIONAL DISTILATION
  • The different compounds in the crude oil have different boiling points
  • The compounds are called hydrocarbon molecules (made of hydrogen and carbon)
  • The smallest hydrocarbons have the lowest boiling and cooling points
  • The smallest are also highly flammable so are good for fuels
  • The longest have low flammability and a high boiling and cooling point
In a fractionating column, crude oil vapour is pumped into the bottom where the temperature is the hottest and the larger molecules feed off as they cool at the higher temperatures. The temperature at the top is the lowest so this is where the smaller hydrocarbons condense and feed off (the thinner fuels)



Alkanes

These hydrocarbons are called ALKANES which contain NO double bonds and have a general rule for the number of carbon to hydrogen ratio... Cn H2n+2 so if you have 2 carbons you will have double that, add two = 6 hydrogens. They are SATURATED because they have no double bonds.

The first four shortest alkanes are METHANE, ETHANE, PROPANE, BUTANE.




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