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Chemistry > 8. Fuels and Earth Science > Flashcards

8. Fuels and Earth Science Flashcards

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1
Q

What are hydrocarbons?

A

Compounds that contain hydrogen and carbon atoms only.

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2
Q

What is crude oil?

A
  • A complex mixture of hydrocarbons.
  • Contains molecules with rings of chains of carbon atoms.
  • An important source of useful substances like fuels and feedstocks for the petrochemical industry.
  • A finite resource.
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3
Q

Where can crude oil be found?

A

Under the sea and under the ground.

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4
Q

What does it mean when crude oil is described as a ‘finite’ resource?

A

It will run out.

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5
Q

How can crude oil be separated?

A

Fractional distillation

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6
Q

How does the process of fractional distillation work to separate crude oil?

A
  • Crude oil is vaporised before it enters a fractionating column.
  • The fractionating column is hotter at the bottom that at the top. The vapours rise up and condense at different fractions depending on their boiling points.
  • Hydrocarbons with low boiling points will be tapped off the top of the column and hydrocarbons with high boiling points will be tapped off at the bottom of the column.
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7
Q

Why is crude oil separated?

A

Unseparated crude oil isn’t very useful but the separated products (such as petrol) are very useful.

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8
Q

Refinery gas is a fraction of crude oil. What are its common uses?

A

Heating and cooking

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9
Q

Which fraction of crude oil is used as fuel in cars?

A

Petrol.
Diesel is also less commonly used.

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10
Q

Kerosene is a fraction of crude oil. What is a common use of kerosene?

A

Aircraft fuel

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11
Q

Diesel oil is a fraction of crude oil. What is it commonly used for?

A

Fuel for some cars and trains.

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12
Q

Which fraction of crude oil is used for road surfacing and roofs?

A

Bitumen

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13
Q

Fuel oil is a fraction of crude oil. What is it commonly used for?

A

Fuel for large ships and in some power stations.

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14
Q

How do the hydrocarbons at each fraction differ?

A
  • Boiling points.
  • Ease of ignition.
  • Viscosity.
  • The number of hydrogen and carbon atoms their molecules have.
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15
Q

Where in the fractionating column do hydrocarbons with the highest viscosity condense?

A

Viscosity is how thick and sticky a substance is.

The hydrocarbons with the highest viscosity (like bitumen) are collected at the bottom of the fractionating column.

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16
Q

What are the properties of hydrocarbons that are tapped from the top of the fractionating column, like petrol and refinery gas?

A
  • Low boiling point.
  • Highly volatile.
  • Easily ignited.
  • Shorter hydrocarbon chains (small molecules).
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17
Q

What is a homologous series?

A

Series of compounds which:
- Have the same general formula.
- Have similar chemical properties.
- Differ by CH₂ in molecular formula form neighbouring molecules.
- Slight variation in physical properties.

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18
Q

Products from crude oil mostly belong to which homologous series?

A

Alkane homologous series.

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19
Q

What are the only products when a hydrocarbon fuel undergoes complete combustion?

A

Water (H₂O) and carbon dioxide (CO₂).

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20
Q

TRUE OR FALSE: Energy is given out when a fuel undergoes complete combustion.

A

True - the reaction is exothermic.

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21
Q

Write a balanced symbol equation for the complete combustion of ethane.

A

2C₂H₆ + 7O₂ —> 4CO₂ + 6H₂O

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22
Q

What is complete combustion?

A

A reaction that occurs when a fuel reacts with excess oxygen.

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23
Q

Write the word equation for complete combustion.

A

Hydrocarbon + Oxygen —> Carbon dioxide + Water

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24
Q

When does incomplete combustion occur?

A

Incomplete combustion occurs when there is an insufficient supply of oxygen.

25
Q

What are the products of incomplete combustion?

A
  • Carbon particulates - soot (C)
  • Carbon monoxide (CO)
  • Water (H₂O)
26
Q

Write a balanced symbol equation for the incomplete combustion of methane to form carbon monoxide.

A

2CH₄ + 3O₂ —> 2CO + 4H₂O

27
Q

Write a balanced symbol equation for the incomplete combustion of methane to form carbon particulates (soot)

A

CH₄ + O₂ —> C + 2H₂O

28
Q

What are the problems with carbon monoxide?

A

Carbon monoxide is a toxic gas.

It is colourless and odourless and if breathed in it can cause death by preventing the red blood cells from carrying oxygen around the body.

29
Q

What are the problems with incomplete combustion?

A
  • Produces carbon monoxide which is toxic and can be fatal if breathed in.
  • Produces carbon particulates (soot) which cause global dimming, reduces air quality, and causes respiratory problems.
30
Q

Why is sulfur dioxide sometimes produced when burning hydrocarbon fuels?

A

Some hydrocarbon fuels contain sulfur impurities. When the fuel is burned, the sulfur reacts with oxygen to form sulfur dioxide.

31
Q

How is acid rain produced?

A

Sulfur dioxide (produced when combusting impure hydrocarbon fuels) evaporates into the air. It reacts with water in the clouds to form sulfuric acid. This is ‘acid rain’.

32
Q

What problems can acid rain cause?

A
  • Corrodes buildings and statues made of limestone.
  • Kills/damages the vegetation.
  • Lowers the pH of large bodies of water, killing the wildlife.
33
Q

How are oxides of nitrogen produced from car engines?

A

The high temperature and pressure of a car engine causes nitrogen and oxygen from the air to react together.

34
Q

What problems are associated with oxides of nitrogen?

A
  • Pollutants.
  • Produce acid rain with similar effects as SO₂.
  • Cause respiratory problems.
35
Q

What are the advantages of using hydrogen as a fuel in cars?

A
  • It releases more energy per kg compared to most other fuels.
  • Water is the only product so no pollutants.
  • Renewable source as hydrogen can be extracted from water.
36
Q

What are the disadvantages of using hydrogen as a fuel in cars?

A
  • It is expensive to produce and a lot of energy is required for the electrolysis of water to acquire the hydrogen.
  • Difficult and dangerous to store hydrogen because it is very volatile and easily ignites.
37
Q

Name the non-renewable fossil fuel found in natural gas.

A

Methane

38
Q

Are petrol, kerosene, and diesel renewable fuels?

A

No, they are non-renewable. They are finite resources which are not being readily replaced.

39
Q

What is the order of each fraction of crude oil that condenses during fractional distillation (from bottom to top)?

A

Bottom: bitumen
fuel oil
diesel oil
kerosene
petrol
Top: refinery gas

40
Q

What is cracking?

A

Breaking down long-chain hydrocarbons into smaller, more useful ones.

Saturated alkanes are cracked into shorter-chain alkanes and short-chain unsaturated alkenes.

41
Q

What does the term ‘saturated’ mean?

A

Only contains single bonds.

42
Q

What does the term ‘unsaturated’ mean?

A

Contains some C=C double bonds.

43
Q

What type of reaction is cracking?

A

Thermal decomposition

44
Q

Why is cracking necessary?

A

The demand for shorter chain alkenes and alkanes is much greater than the demand for long chain alkanes.

45
Q

What produced the gases that formed Earth’s early atmosphere?

A

Volcanic activity

46
Q

Describe how Earth’s early atmosphere formed.

A
  • Initially, the Earth’s surface was molten with no atmosphere.
  • Cooling caused land masses to solidify.
  • Volcanoes formed on the land masses and released gases which formed the early atmosphere.
47
Q

What was the Earth’s early atmosphere though to contain?

A
  • Little or no oxygen.
  • Large amount of carbon dioxide.
  • Water vapour.
  • Small amounts of other gases.
48
Q

How did oceans initially form?

A

Condensation of water vapour.

49
Q

How did the amount of carbon dioxide in the early Earth’s atmosphere decrease after oceans formed?

A

Carbon dioxide dissolved into the oceans so the amount of carbon dioxide in the atmosphere decreased.

50
Q

How did the amount of oxygen in the early Earth’s atmosphere increase?

A

The growth of early plants used carbon dioxide for photosynthesis and released oxygen. This increased the amount of oxygen and decreased the amount of carbon dioxide in the atmosphere.

51
Q

What is the chemical test for oxygen?

A

Insert a glowing splint into a test tube of gas. If oxygen is present, the splint will ignite.

52
Q

What are greenhouse gases?

A

Various gases in the atmosphere (such as carbon dioxide, methane and water vapour) that absorb the heat radiated from Earth.

53
Q

What is the greenhouse effect?

A
  • Electromagnetic radiation from the sun passes through the Earth’s atmosphere.
  • The Earth absorbs some radiation and warms up.
  • Heat is radiated from the Earth as infrared radiation.
  • Some of the infrared radiation is absorbed by greenhouse gases in the atmosphere which warms the atmosphere.
54
Q

How has human activity increased atmospheric carbon dioxide concentration?

A
  • Burning fossil fuels for energy releases carbon dioxide.
  • Deforestation reduces the amount of photosynthesis occurring so less carbon dioxide is converted to oxygen.
55
Q

What is the current composition of Earth’s atmosphere?

A

Nitrogen - 78%
Oxygen - 21%
Argon - 0.93%
Carbon - 0.04%

56
Q

What are the effects of global warming?

A
  • Melting of polar ice caps.
  • Difficulties acquiring drinking water.
  • Flooding.
  • Forest fires.
  • Destruction of ecosystems.
57
Q

How has human activity increased the amount of methane in the atmosphere?

A
  • Raising livestock such as cows.
  • Decay of organic waste in landfill sites.
58
Q

How can the effects of global warming be mitigated?

A
  • Construct flood defences in areas of low lying land.
  • Use of irrigation systems to provide water in drought.
  • Produce alternative crops which are better adapted to the new environment.
59
Q

Evaluate the evidence that human activity is causing climate change.

A
  • There is a correlation between carbon dioxide concentration in the atmosphere, fossil fuel consumption and temperature change.
  • Correlation doesn’t mean causation.
  • There may be uncertainties in the historical data (e.g. location of the measurements and historical accuracy).

Chemistry (7 decks)

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