What are hydrocarbons?
-any compound that contains carbon and hydrogen only
What are alkanes?
- saturated compounds (one single convalent bond)
- will not form polymers
- CnH2n+2
What are alkenes
- unsaturated compounds (at least one double bond)
- double bonds can open and join onto things , making alkenes more reactive than alkanes
- CNH2n
How are double bonds formed?
-two atoms sharing two pairs of electrons instead of one pair
How can you test if a hydrocarbon is an alkene?
- react alkene with bromine water
- shake them together and if the bromine water goes from orange to colourless, it is an alkene
- this is an addition reaction
- bromine adds to the alkene with a double bond to make a colourless dibromo solution
- bromine water has decolourised
What are the fractions of crude oil?
-LPG (liquefied petroleum gas)
-petrol
-napatha
-kerosene (paraffin)
-diesel
-oil (fuel oil, heating oil, lubricating oil)
-bitumen
each fraction contains a mixture of hydrocarbon with similar boiling points
How is crude oil separated into different hydrocarbon fractions?
-factional distillation
1-oil is heated until mostly gas
2-gases enter the bottom of the factional distillation column (has a temperature gradient)
3-bitumen drains off at the bottom as it is a liquid at the hottest bottom (hot)
-the longer the hydrocarbon the higher the boiling point, turn into liquids and drain out of the column earlier on, near the bottom
-the shorter the hydrocarbon the lower the boiling point, liquefy and drain out nearer the top later on, where it is cooler
How do hydrocarbon properties change as the size increases?
- boiling point increases
- less flammable
- more viscous (doesn’t flow as easily)
- less volatile
What is crude oil?
- formed from fossils of plants and animals and turn to crude oil by high temperature and pressure
- mixture of lots of different hydrocarbons
What important types of bonds are in crude oil?
- strong covalent bonds between carbons and hydrogen within each hydrocarbon molecule
- intermolecular forces of attraction between different hydrocarbon molecules
Why do the properties of crude oil change?
-the longer the hydrocarbon, the stronger the intermolecular forces, the higher the boiling and melting point
