Crude Oil And Fossil Fuels Flashcards
How is crude oil formed?
Crude oil is formed from the remains of small animals and plants that died and fell to the bottom of the sea. Their remains were covered by mud. As the sediment was buried by more sediment, it started to change into rock as the temperature and pressure increased. This rock put a lot of pressure on the dead animals and plants. Rocks around them also heated them up. Together the heat and the pressure turned the remains into crude oil. It was important that no air or oxygen was present.
Composition of crude oil?
A mixture of hydrocarbons
What is fractional distillation?
A tall column is fitted above the crude oil, with several condensers coming off at different fractions. The column is hot at the bottom and cool at the top. Hydrocarbons with high boiling points condense at the bottom and substances with lower boiling points condense on the way to the top.
Therefore each fraction contains hydrocarbon molecules with a similar number of atoms.
As you go up the fractionating column the hydrocarbons have…
(Properties)
Lower boiling points
Lower viscosity
Higher flammability
Why is fractional distillation used to separate crude oil?
Because hydrocarbons have different boiling points so they can be separated using this.
What is a hydrocarbon?
Organic compounds containing hydrogen and carbon
What is an alkene?
Hydrocarbons with double the number of hydrogen atoms than carbon.
What is the general formula for working out how many hydrogen atoms are in a homologen.
No of hydrogen atoms x 2 then + 2
Cn H2n +2
First four alkanes
Methane, ethane, propane and butane
What are the different fractions in the fractionating column
Lowest boiling point to highest.
Gases Gasoline Naphtha Kerosene Gas oil Lubricants and wax Fuel oil
Properties of hydrocarbons with small molecules
Very volatile
Flows easily
Very flammable
Properties of hydrocarbons with large molecules
High boiling point
Not very volatile
Does not flow easily
Not very flammable
Difference between complete and incomplete combustion
Complete combustion happens in a plentiful supply of air. Incomplete combustion occurs when the supply of air is limited.
What is cracking?
Cracking allows large hydrocarbon molecules to be broken down into smaller, more useful hydrocarbon molecules. Fractions containing large hydrocarbon molecules are vaporised and passed over a hot catalyst. This breaks chemical bonds in the molecules, and forms smaller hydrocarbon molecules.
What is an alkene
A hydrocarbon containing a double carbon bond
