Chapter 23: Crude Oil

Question 1

What is crude oil?

Answer 1

a mixture of HYDROCARBON molecules of different sizes.

Question 2

How do the physical properties of crude oil change as the number of carbons in the hydrocarbon molecules increase?

Answer 2

• the intermolecular forces get stronger, so require more energy to break
• the boiling points increase (they become less volatile)
• they become more viscous (flow less easily)
• they become darker in colour

Question 3

How does the industrial process of fractional distillation separate crude oil into fractions?

Answer 3

• crude oil is heated and the vapours are pumped into the bottom of a fractionating column
• the fractionating column is hotter at the bottom and gets cooler towards the top
• the vapours rise, cool and condense at different heights depending on their boiling points

Question 4

Uses of the fractions of crude oil: Refinery gas

Answer 4

• is a mixture of methane, ethane, propane and butane

- used as LPG for domestic heating + cooking

Question 5

Uses of the fractions of crude oil: petrol

Answer 5

Fuel in cars

Question 6

Uses of the fractions of crude oil: kerosene

Answer 6

• fuel for jet aircrafts
• domestic heating oil
• “paraffin” for small heaters + lamps

Question 7

Uses of the fractions of crude oil: diesel

Answer 7

Fuel for vehicles ( or can be converted to petrol)

Question 8

Uses of the fractions of crude oil: fuel oil

Answer 8

• fuel for ships or industrial heating

Question 9

Uses of the fractions of crude oil: bitumen

Answer 9

melted + mixed with rocks to make the top surface of roads

Question 10

What is a fuel?

Answer 10

• a substance that releases heat energy when burned
• hydrocarbons make good fuels
• when burnt, they react with oxygen to produce carbon dioxide and water

Question 11

What can happen in car engines?

Answer 11

• temperature is high enough for nitrogen and oxygen from the air to react and form oxides of nitrogen
• these react to form nitric acid which also causes acid rain

Question 12

How can the burning of hydrocarbons lead to acid rain?

Answer 12

• sulphur is an impurity in hydrocarbon (fossil) fuels
• when the fuel is burnt, sodium dioxide is formed
• this reacts with water and oxygen in the air to form sulphuric acid which causes acid rain

Question 13

Why do we use catalytic cracking on crude oil fractions

Answer 13

the demand for petrol is greater than the supply from fractional distillation of crude oil, so some of the larger fractions, which there are too many of, are converted into smaller, more useful molecules for cracking. This type of reaction is thermal decomposition.

Question 14

Word equation for cracking

Answer 14

Long- chain alkane -> shorter chain alkane + alkene (used to make polymers/plastics)

Question 15

What conditions are needed for catalytic cracking of crude oil fractions?

Answer 15

• high temperature (600-700 degrees C)

- using silicon dioxide and aluminium oxide catalysts