C1.4 Crude oil and fuels

Question 1

What is crude oil?

Answer 1

A mixture of compounds which are hydrocarbon molecules

Question 2

Define ‘mixture’

Answer 2

Two or more elements/compounds not chemically combined, with the chemical properties of each substance unchanged

Question 3

Where is crude oil derived from?

Answer 3

An ancient biomass found in rocks

Question 4

What is the general formula for alkanes?

Answer 4

Cn H2n+2

Question 5

What are alkanes?

Answer 5

Saturated hydrocarbons with as many hydrogen atoms as possible bonded to each carbon

Question 6

What are the first four alkanes and their formulas?

Answer 6

• Methane (CH4)
• Ethane (C2H6)
• Propane (C3H8)
• Butane (C4H10)

Question 7

Explain the process of fractional distillation.

Answer 7

• Crude oil is heated to 350c degrees and vaporised
• As vapours rise up the fractionating column they cool and condense
• The hydrocarbons are different lengths so their vapors condense at different times at different points in the column
• They are trapped off as liquids at the levels they condense in the column

Question 8

What is similar about fractions from crude oil?

Answer 8

They have a similar number of carbon atoms

Question 9

What do the properties of hydrocarbons depend on?

Answer 9

The length of their molecules

Question 10

The shorter the hydrocarbon molecule…

Answer 10

• The less viscous
• The more volatile
• The lower the boiling/melting point
• The more flammable

Question 11

What do most fuels contain?

Answer 11

• Carbon
• Hydrogen
• May also contain sulfur

Question 12

What is usually released when fuels are burnt?

Answer 12

• Carbon dioxide
• Water vapour
• Carbon monoxide
• Nitrogen oxide (at very high temperatures)
• Sulphur dioxide
• Solid particles (soot)

Question 13

What happens during the combustion of hydrocarbon fuel?

Answer 13

• Energy is released

- The carbon and hydrogen in the fuels are oxidised

Question 14

What is combustion?

Answer 14

A chemical reaction of a fuel with oxygen that releases energy

Question 15

What are advantages of using crude oil?

Answer 15

• Most modern transport is fueled by a crude oil fraction
• So is central heating and electricity
• It is a large industry
• Many materials e.g plastics are made from crude oil
• Most machinery is set up for oil fractions e.g cars and they are readily available e.g many petrol stations
• More reliable than eco alternatives e.g wind turbines

Question 16

What are disadvantages of using crude oil?

Answer 16

• Non-renewable
• Oil spills disrupt environment and animals e.g sea otters and birds are poisoned
• Burning it causes global warming, acid rain and global dimming (more detail later)

Question 17

What do carbon dioxide emissions cause?

Answer 17

• A rise in global temperature

- This means changing rainfall patterns and flooding

Question 18

When does a fuel release sulphur dioxide?

Answer 18

If it contains sulphur impurities

Question 19

What do sulphur dioxide emissions cause?

Answer 19

• They mix with water in clouds to make sulfuric acid
• This falls as acid rain
• This kills trees and damages limestone buildings

Question 20

How can acid rain be reduced?

Answer 20

• By removing sulphur from the fuel (this is expensive and uses more energy though)
• By putting acid gas scrubbers in petrol stations to take harmful gases out before they are released into the atmosphere

Question 21

What do nitrogen oxide emissions cause?

Answer 21

• Acid rain in clouds as well (nitric acid)

- Smog

Question 22

What is incomplete combustion?

Answer 22

When there is not enough oxygen and some of the fuel doesn’t burn

Question 23

What does soot cause?

Answer 23

• Global dimming
• The particles reflect sunlight back into space
• They also produce more clouds which reflect sunlight back into space

Question 24

What does carbon monoxide cause?

Answer 24

It is a poison to humans, reducing the amount of oxygen carried by the blood

Question 25

Give 3 examples of alternative fuels being developed.

Answer 25

• Ethanol
• Biodiesel
• Hydrogen gas

Question 26

How is ethanol made and what is it used for?

Answer 26

The fermentation of plants

- To power cars

Question 27

What are the advantages of ethanol?

Answer 27

• Carbon neutral

- Only product other than carbon dioxide is water

Question 28

What are the disadvantages of ethanol?

Answer 28

• Engines need to be converted
• Ethanol fuel not widely available
• Increase in food prices as land is used to grow fuel crop

Question 29

How is biofuel made and what is it used for?

Answer 29

• Produced from vegetable oils e.g rapeseed oil and soybean oil
• To run a biodiesel engine

Question 30

What are the advantages of biofuel?

Answer 30

• Carbon neutral
• No need to convert engines
• Less sulphur dioxide and soot than ordinary diesel

Question 31

What are the disadvantages of biofuel?

Answer 31

• Not enough to completely replace diesel
• Expensive
• Increase in food prices

Question 32

How is hydrogen acquired and what is it used for?

Answer 32

• From the electrolysis of water

- To power vehicles

Question 33

What is the advantage of hydrogen gas?

Answer 33

• Hydrogen combines with oxygen in the air to form just water (very clean)

Question 34

What are the disadvantages of hydrogen gas?

Answer 34

• Special, expensive engine needed
• Hydrogen not widely available
• Hard to store
• Electrolysis needed = energy