Aim: The aim of this experiment is break a larger alkane into smaller alkanes and alkenes.
Theory: Fuels made from oil mixtures containing large hydrocarbon molecules are not efficient. They do not flow easily and are difficult to ignite. Crude oil often contains too many large hydrocarbon molecules and not enough small hydrocarbon molecules to meet demand.
Cracking allows large hydrocarbon molecules to be broken down into smaller, more useful hydrocarbon molecules. Fractions containing large hydrocarbon molecules are vaporized and passed over a hot catalyst. This breaks chemical bonds in the molecules, and forms smaller hydrocarbon molecules.
Some of the smaller molecules formed by cracking are used as fuels, and some of them are used to make polymers in plastics manufacture.
The hydrocarbon molecules are broken up in fairly random ways to produce mixtures of smaller hydrocarbons, some of which have carbon-carbon double bonds. One possible reaction involving the hydrocarbon C15H32 might be:
Apparatus: eye protection, 2 test tubes, boiling tube, delivery tube, stopper, Bunsen burner, pipette, bromine water, lava rocks, air tube, clamp, paraffin oil, wool, stand, trough, water
Hypothesis: We will collect the alkanes and alkenes in a test tube and when we put bromine water in, the water will turn from yellow to transparent in the presence of an alkene.
1. Place some wool in the back of the boiler tube. Using a pipette, place a few drops of paraffin oil onto the wool.
2. Put in the boiler tube a handful of lava rocks, in the center of the tube and not touching the wool.
3. Place the stopper in the boiler tube and attach it to the stand.
4. Fill the trough about two-thirds full with water and put the delivery tube in the stopper of the boiler tube. Position the trough so that the delivery tube is immersed in the water.
5. Take a test