Section 8 - Fuels & Earth Science

Question 1

What is crude oil?

Answer 1

A complex mixture of lots of different hydrocarbons found underground formed from the remains of plants and animals.

Question 2

What are hydrocarbons?

Answer 2

Compounds made of only hydrogen and carbon.

Question 3

How are the carbon atoms in the hydrocarbons found in crude oil often arranged?

Answer 3

Often as chains or rings

Question 4

What are the various parts of crude oil called?

Answer 4

Fractions.

Question 5

What type of hydrocarbon is the most common in crude oil?

Answer 5

Alkanes.

Question 6

What process is used to separate the parts of crude oil?

Answer 6

Fractional distillation.

Question 7

how does fractional distillation work?

Answer 7

The different fractions in a mixture condense at different temperatures, so the mixture is heated until most of it turns into gas. due to a temperature gradient in the fractionating column, the gasses condense at different heights, separating the mixture into its fractions.

Question 8

describe the temperature gradient in a fractionating column.

Answer 8

The column gets cooler going up the column.

Question 9

Describe the trend between hydrocarbon length and their boiling and melting points.

Answer 9

Longer hydrocarbons have higher boiling and melting points.

Question 10

List some crude oil fractions, their approximate number of carbon atoms and their uses.

Answer 10

3, gases, used in domestic heating and cooking.
8, petrol, used as fuel for cars.
15, kerosene, used as aircraft fuel.
20, diesel oil, used as fuel for some cars and larger vehicles like trains.
40, fuel oil, used as fuel for large ships and some power stations.
70, bitumen, used to surface roads and roofs.

Question 11

What is a homologous series?

Answer 11

A family of molecules which share a general formula and have similar chemical properties.

Question 12

What are some examples of a homologous series?

Answer 12

Alkanes and alkenes.

Question 13

Why does hydrocarbon size affect the molecule’s properties?

Answer 13

Longer hydrocarbons have more intermolecular bonds between them because there are more bonds it takes more energy to separate the molecules from another, this raises the boiling points and melting points as well as the viscosity of the molecules, it also makes them harder to ignite than smaller hydrocarbons as well.

Question 14

How do fuels release energy?

Answer 14

Through combustion reactions.

Question 15

What are the products of a complete combustion reaction?

Answer 15

Carbon dioxide and water.

Question 16

What are the products of incomplete combustion reaction?

Answer 16

Carbon dioxide, water, carbon monoxide and carbon in the form of soot.

Question 17

What are the dangers of carbon monoxide?

Answer 17

Carbon monoxide combines with red blood cells and prevents the absorption of oxygen, this stops oxygen getting to your cells. A lack of oxygen to the brain can cause fainting coma and death.

Question 18

What are the dangers of soot?

Answer 18

Soot reduces air quality and can cause or worsen respiratory problems, which can be dangerous to young children and babies especially. It also makes the area it collects look dirty.

Question 19

What are the two common additional products of fossil fuel burning?

Answer 19

Sulfur dioxide and various nitrogen oxides.

Question 20

What are the issues caused by sulfur dioxide?

Answer 20

Sulfur dioxide mixes with clouds, forming dilute sulfuric acid, which falls as acid rain. This causes lakes and other bodies of water to become more acidic, which kills off many plants and animals as a result. Acid rain also kills trees, damages limestone buildings, stone statues as well as corroding some metals.

Question 21

What are the issues caused by nitrogen oxides?

Answer 21

Nitrogen oxides can lead to acid rain as well as cause photochemical smog, a type of air pollution that can cause breathing difficulties, headaches and tiredness?

Question 22

How do nitrogen oxides form?

Answer 22

Nitrogen oxides are formed in reactions between oxygen and nitrogen in the air, caused by the energy released by combustion engines like in the internal combustion engines of cars.

Question 23

What are the benefits of using hydrogen gas as a fuel?

Answer 23

It is non-polluting since the only product is water, the hydrogen is also obtained from water, which makes it a renewable resource, which means it will never run out, unlike fossil fuels.

Question 24

What are the drawbacks of using hydrogen gas as a fuel?

Answer 24

It requires a special, expensive engine to use, it is expensive to produce and requires energy from an alternative source. Hydrogen is also difficult and sometimes dangerous to store.

Question 25

What is cracking?

Answer 25

The process of splitting long-chain hydrocarbons into smaller, more useful molecules through thermal decomposition.

Question 26

What is thermal decomposition?

Answer 26

A process where a molecule breaks down into at least two smaller molecules when it is heated.

Question 27

Why is cracking used?

Answer 27

There is often a higher demand for smaller chain molecule, like those in petrol, than longer ones, like those in bitumen, so to keep up with demand, producers often break long-chain molecules into higher demand fractions.

Question 28

What are the products of cracking?

Answer 28

A smaller alkane molecule and a small alkene molecule?

Question 29

What are alkenes used for?

Answer 29

The production of polymers.

Question 30

What is required for cracking to occur?

Answer 30

Heat, between 400°C and 700°C, pressure, about 70 atm, and a catalyst, aluminium oxide.

Question 31

Describe phase 1 of the development of Earth's atmosphere.

Answer 31

Earths surface was originally molten. After millions of years, the outside cooled and formed a thin crust. Volcanoes formed and continued erupting releasing mainly CO₂ as well as steam, methane and ammonia. The water vapour condensed to form the oceans.

Question 32

Describe phase 2 of the development of Earth's atmosphere.

Answer 32

A lot of CO₂ dissolved into the oceans. Nitrogen gas entered the atmosphere due to the ammonia reacting with oxygen as well as through denitrifying bacteria. Nitrogen gas isn't very reactive so the amount in the atmosphere increased because it was being formed but not used. Green plants evolved across the earth. As the plants photosynthesized CO₂ was removed and more oxygen was introduced. The O₂ built up over time. Lots of the CO₂ was locked up in sedimentary rocks and fossil fuels.

Question 33

Describe Phase 3 of the development of Earth's atmosphere.

Answer 33

The oxygen build-up killed off early organism that couldn't tolerate it The oxygen also allowed for the evolution of more complex organisms that made use of it. Ozone, O₃, was formed which blocked the sun's more harmful rays, allowing even more complex organisms to evolve. There is virtually no CO₂ left at this point.

Question 34

How do you test for oxygen?

Answer 34

By holding a glowing splint in the gas, if the splint relights oxygen must be present.

Question 35

What is the greenhouse effect?

Answer 35

How the earth's atmosphere prevents heat from re-emitting into space.

Question 36

What are greenhouse gasses? List some examples.

Answer 36

Gasses present in Earth's atmosphere that can absorb and reflect heat radiation. Examples include carbon dioxide, water vapour and methane.

Question 37

How does the greenhouse effect work?

Answer 37

The sun emits electromagnetic radiation Some of this radiation passes through the atmosphere. The Earth's surface absorbs lots of the shorter wavelength radiation. The Earth radiates some of the heat radiation as longer wavelength infrared (IR) radiation. Some of the IR radiation is absorbed by the greenhouse gasses. Some of the IR radiation is reflected back to the Earth by the greenhouse gasses. Some of the IR radiation is re-emitted back into space. The absorption and reflection of IR radiation keeps the earth warm.

Question 38

Why has global warming increased rapidly recently?

Answer 38

Over the last 150 years, the human population has increased rapidly. More energy is required to keep up with demand, especially due to industrialisation. More fossil fuels are burned as a result. More people requires more housing so more trees are cut down to make space- known as deforestation. This has led to more CO₂ in the atmosphere because more is being produced than taken out by plants and trees. This has led to an enhanced greenhouse effect which has heated the atmosphere.

Question 39

What problems are caused by global warming?

Answer 39

Climate change, flooding, due to rising sea levels from the melting ice caps as well as the destruction of certain habitats.

Question 40

Why has more methane entered the atmosphere? Why is this a problem?

Answer 40

Due to increased livestock farming, more methane producing animals are being bred, this has led to more methane in the atmosphere which has contributed to global warming.

Question 41

Why is historical climate data much less accurate than current records?

Answer 41

Current global temperature and CO₂ levels can be worked out accurately through measurements taken from across the world. Historical data can only be gathered from a few places, by analysing fossils, tree rings or the gas bubbles trapped in ice sheets to estimate past levels of CO₂. These methods are much less precise than current measurements made using instrument sampling, they also are less representative of global levels.

Question 42

How can climate change be prevented or slowed down?

Answer 42

Reducing the use of fossil fuels either on a personal level, like replacing driving with walking or cycling and central heating with blankets or a larger scale, like government action to encourage the development of more energy efficient appliances and more renewable energy sources, like solar power.