5.13 i can describe catalytic cracking of long-chain hydrocarbons

a. Define the term catalyst

A substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change.

b.Why is a catalyst used?
To speed up the rate of reaction
c. Why are high temperatures needed?
To separate the hydrogens and the carbons, also high temperatures help speed up the reactions

d.
1. What is the process called when you break long chained hydrocarbons in to shorter ones?
Cracking
2. Why is the catalyst used in this experiment?
The catalyst will speed up the reaction  
3.  How is Paraffin broken down?
By applying heat onto the Paraffin
4.  How is the Paraffin Collected?
Over water and into a test tube facing down into the water
5.  What is the main thing you have to try and avoid in this experiment?
Water sucking back up the tube and into the test tube 
6.  Why is this dangerous?
Allowing the water to suck back and into the hot test tube would turn the water into steam and this may cause an explosion
7. Why aren't the first few bubbles produced collected in the experiment above?
This is because the first few bubbles are formed by the air inside the test tube expanding not the Paraffin.
8. Why do we crack long chained hydrocarbons
This is because most long chained hydrocarbons are useless and we get a lot of this material from fractional distillation and not enough of the short chained hydrocarbons which are more useful to us. This is why we crack the long chained hydrocarbons to produce the more useful short chained hydrocarbon.