Cracking Crude Oil

Question 1

After you have fractionally distilled crude oil, what are you left with?

Answer 1

Still both long and short hydrocarbons, but just not all mixed together

Question 2

What does ‘cracking’ mean?

Answer 2

Splitting up long-chain hydrocarbons

Question 3

Why do we crack long-chain hydrocarbons?

Answer 3

To produce shorter, more useful substances

Question 4

Long-chain hydrocarbons form ____ ____ ____ like ____, which isn’t very ____ at all.

Answer 4

Long-chain hydrocarbons form thick, gloopy liquids like tar, which isn’t very useful at all.

Question 5

Name 3 substances produced by cracking and their uses

Answer 5

1. Petrol - as fuel for cars
2. Paraffin - as fuel for jets
3. Ethene - for making plastics

Question 6

How does cracking work?

Answer 6

By passing a vapourised long-chain hydrocarbon over a hot catalyst

Question 7

What kind of a reaction if cracking?

Answer 7

Thermal decomposition

Question 8

Explain what is meant by the phrase ‘Cracking is a thermal decomposition reaction’

Answer 8

It involves breaking down molecules by heating them

Question 9

What are the 3 steps to cracking?

Answer 9

1. Heat the long-chain hydrocarbon to vapourise it
2. Pass the vapour over a powdered catalyst (aluminium oxide) at a temperature of about 400-700^oC
3. The long-chain molecules split apart or ‘crack’ on the surface of the specks of catalyst

Question 10

What are the 2 conditions needed for cracking?

Answer 10

1. Passed over a powdered catalyst of aluminium oxide
2. At 400^oC - 700^oC

Question 11

What is an alternative way to crack long-chain hydrocarbons?

Answer 11

Mixing the vapour with steam at a very high temperature

Question 12

What are the 2 main products of carcking?

Answer 12

1. Alkanes
2. Alkenes

Question 13

Draw the craking of hexane (long-chain hydrocarbon) into butane (alkane) and ethene (alkene)

Answer 13

Question 14

What is octane used for?

Answer 14

Petrol