Chapter 18 - Fuels and Crude Oil

Question 1

Describe how fossil fuels come about

Answer 1

1) Millions of years ago, tiny sea creatures sank to the seabed after death
2) They were covered by mud and sand
3) Heat from Earth + pressure from the compressing rocks acted on the organisms producing fossil fuels
4) E.g. crude oil & natural gas

Question 2

Describe fossil fuels

Answer 2

• Fossil fuels are formed form decayed plants and animals from millions of years ago
• Mainly organic compounds containing only carbon & hydrogen (aka hydrocarbons)
• Fossil fuels are burnt in presence of O2 to form CO2 + H2O + thermal energy
• Exothermic/Combustion reaction
• Thermal energy converted to other forms of energy

Question 3

Describe natural gases

Answer 3

• Fossil fuel consisting mainly methane
• Odourless & colourless
• When methane is burnt in excess O2, CO2 + H2O is produced
• Cleanest gas
• Liquefied for transport to become LNG as it does not burn easy = X danger
• Additive THT added for pungent smell to detect gas leak

Question 4

Describe crude oils (aka petroleum)

Answer 4

• Contains mixture of hydrocarbons
• Found beneath land (underground deposits) /ocean floor, thousands of metres below Earth’s surface
• Extracted crude oil has different types of hydrocarbons separated into groups based on its properties
• e.g. burns under same conditions = 1 group
• e.g. used as starting materials to synthesise chemicals = a few groups

Question 5

Define non renewable source of energy

Answer 5

Natural gas and crude oil are considered non renewable sources of energy. Limited amounts of these sources + can’t be replaced fast enough to keep up with our rate of use

Question 6

Where is crude oil sent to be separated into individual components?

Answer 6

Oil refineries

Question 7

What do oil refineries use to separate crude oils and why?

Answer 7

They use fractional distillation to separate crude oils into various fractions because of the hydrocarbons present in crude oil have different boiling points and are miscible

Question 8

Crude oil is separated into ____ ____ by fractional distillation

Answer 8

useful fractions

Question 9

In fractional distillation, what would the positions of substances with lower and higher boiling points?

Answer 9

Lower boiling points = higher/closer to the top collected at top most outlet)
Higher boiling points = lower/closer to the bottom (collected at bottom outlet)

Question 10

Crude oil contains hydrocarbons with ____ to ____ carbon atoms per molecule

Answer 10

1 to 70

Question 11

How does the boiling point of hydrocarbons relate to the number of carbon atoms in each molecule?

Answer 11

Higher bp = more carbon atoms
Lower bp = less carbon atoms

Question 12

Describe hydrocarbons with lower and higher boiling point

Answer 12

Lower bp = less viscous + burn more easily
Higher bp = more viscous + burn less easily

Question 13

Describe how crude oil fractions are separated

Answer 13

1) Crude oil is heated in a furnace to 400°C
2) Boiling occurs and liquid changes into vapour
3) Vapour is passed into the fractionating column
4) Column is hottest at the bottom and gets cooler towards the top
- Fractions with higher bp condense at higher temperature, collected at lower levels
- Fractions with lower bp rise further up the column before they condense and are collected

Question 14

How does the boiling point relate to the number of carbon atoms in hydrocarbons?

Answer 14

Boiling point increases as no. of carbon atoms in hydrocarbons increases

Question 15

What are the 2 competing uses of crude oil?

Answer 15

1) 90% used for fuels to
- generate thermal + electrical energy
- power motor vehicles and industrial activities
2) 10% used as petrochemical feedstock
- manufacture of plastics, detergents, medicines, fertilisers, pesticides, synthetic rubber

Question 16

What is the issue caused by crude oil?

Answer 16

• Supply is limited
• Important as chemical feedstock for manufacture of daily products
• Waste to just ‘burn’ away as fuel
• Compete for limited supply
• To last longer both fuel and chemical feedstock, we need to conserve

Question 17

What are the 3 ways to conserve crude oil?

Answer 17

1) Reduce the use of crude oil by
- reducing number of motor vehicles on the road
- driving smaller cars that consume less fuel
- take public transport
2) Use alternative sources of energy
- alternative fuels
- solar/nuclear energy
3) Improve design of power stations and vehicles such that they use crude oil more efficiently (e.g. electric vehicles)

Question 18

What’s the danger with producing nuclear energy?

Answer 18

Nuclear plants use fuels such as plutonium and uranium. However, there can be harmful radiation leaking into the environment from the nuclear plant