GCSE Chemistry B - OCR - C1

GCSE Chemistry B - OCR - C1

1. Fossil Fuels

   • Examples of fossil fuels: crude oil, coal and natural gas.
   • Formed over millions of years.
   • Finite and non-renewable because they are used up much faster than new supplies can be formed.
   • Can be used as a source of fuel or chemicals.
   • Scientists are now looking for alternatives for crude oil due to it running out quickly.
     • Crude OIl
       • Transported to refineries through pipelines and oil tankers.
         • Oil often spills from the tanker and floats on the sea's surface - this is known as slick and it can harm wildlife and damage beaches.
           • Detergents are used in order to break up oil slicks.
       • The oil affects alot of wildlife. The chemicals are toxic and can harm and kill wildlife.
       • Found in the Earth's crust - pumped to the surface.
       • Is a mixture of hydrocarbons and is formed from dead marine organisms

2. Fractional distillation

   • The process of separating crude oil into useful fractions (parts) that contain mixtures of hydrocarbons with similar boiling points, is called fractional distillation.
     • Crude oil is a mixture of hydrocarbons - a molecule that contains only hydrogen and carbon atoms.
   • Crude oil is heated in a fractionating column.
     • This column has a temperature gradient.
       • This means that, fractions with low boiling points leave at the top of the fractionating column and fractions with high boiling points leave at the bottom of the fractionating column.
   • The order of the fractions (from the fractionating column) from the top to bottom are: liquefied petroleum gas (LPG), petrol (gasoline), paraffin (aircraft fuel), diesel, lubricating oil, fuel oil, bitumen (tar)

3. Cracking

   • Hydrogen molecules can be described as alkanes and alkenes. Large alkane molecules can be broken down into smaller, more useful, alkane and alkene molecules - this is the industrial process called cracking.
   • Needs ta catalyst, a high temperature and high pressure.
   • Used to make more petrol from naptha. It can also be used to make alkene molecules that may be used to make polymers.

4. Forces between molecules

   • A hydrocarbon molecule has: strong covalent bonds between the atoms in the molecue and weak intermolecular forces (this is forces of attraction between molecules).
     • Longer hydrocarbons have stronger intermolecular forces than the forces between shorter hydrocarbons.
   • When a liquid hydrocarbon is boiled, its molecules move faster and faster until all the intermolecular forces are broken and it becomes a gas.
   • Small molecules have very weak forces of attraction between them and are easily overcome by heating.
     • It is their boiling points which allow us to seperate a mixture of hydrocarbons (eg. crude oil) by the process of distillation.

5. Combustion

   • Incomplete combustion
   • Complete Combustion
     • Of a hydrocarbon (fuel)
   • When fuels react with oxygen (in air), they burn snd release useful heat energy.

6. Clean Air

7. Making polymers

   • Designer Polymers

8. Cooking and Food Additives