1. Cracking

2. Short chain hydrocarbons are more useful than longer chain hydrocarbons. We can obtain more short chain hydrocarbons by cracking (breaking) the longer ones.

3. Aim: To investigate the cracking of paraffin Apparatus: Safety goggles Pyrex test tube Soda test tube (x2) Delivery tube Clamp stand Bunsen burner + mat Stopper (x2) Ceramic wool Dropper Chemicals: Paraffin Steel wool

4. Method: Collect test tubes of gas and test with a burning splint and test with bromine water. Also test paraffin with bromine water.

5. Results: Gas collected under water decolourises bromine water. Paraffin doesn’t decolourise bromine water. Conclusion: Since paraffin has changed from a liquid to a gas this suggests that the larger molecules has been broken down into a smaller one. Also the fact that the new substance decolourises bromine water and paraffin doesn’t suggests that a new substance from a different hydrocarbon family has been formed.

6. Long alkane fractions  smaller alkane + alkene (from fractional distillation of crude oil) e.g. C 9 H 20  C 6 H 14 +C 3 H6 C 12 H 26  C 10 H 22 +C 2 H 4

7. Cracking is a process where long chain hydrocarbons are broken down into more useful short chain hydrocarbons. These products are usually a mixture of saturated and unsaturated hydrocarbons. Aluminium oxide is used as a catalyst in this process.