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GCSE Edexcel Separate Chemistry > SC20 Fuels > Flashcards

SC20 Fuels Flashcards

1
Q

Define hydrocarbon

A

A compound that contains hydrogen and carbon only

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2
Q

What is crude oil?

A
  • complex mixture of hydrocarbons of different sizes
  • thick, sticky black liquid that is found in porous rock
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3
Q

What is crude oil used for?

A
  • fuel for vehicles such as aircraft, ship, heating and power stations
  • feedstock or raw materials for the petrochemical industry
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4
Q

Define petrochemicals

A

Substances made from crude oil, such as poly(ethene) and other polymers

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5
Q

Define finite resource

A

Resources that are not made anymore (or are being made extremely slowly) which limits the amount available to us

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6
Q

Why is crude oil a finite resource?

A

It is being used up faster than it is being produced

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7
Q

Why is crude oil important fror the petrochemical industry?

A
  • The fuels that are used in most modern methods of transport are all based on oil products
  • these are all product obtained from crude oil
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8
Q

Define non renewable

A

Fuels that are being used up faster than they can be formed

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9
Q

How is crude oil formed?

A
  • ancient remains of microscopic animals and plants that once lived in the sea
  • became covered in layers of sediments
  • the high temperatures and pressure caused the sediments to turn into rocks, therefore trapping the gas and the oil
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10
Q

How do we separate crude oil into different hydrocarbon?

A

Using fractional distillation

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11
Q

Describe how crude oil is separated by fractional distillation

A
  • crude oil enters fractionating column, so vapours rise
  • vapours with very high boiling points will immediately condense, into liquids lower down and are tapped off
  • vapours of hydrocarbons with low boiling points will rise up and condense at the top of the column
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12
Q

What are the different compounds obtained from crude oil?

A
  • natural gas
  • petrol
  • kerosene
  • diesel oil
  • fuel oil
  • bitumen
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13
Q

Define fractional distillation

A

The separation of a liquid mixture into fractions differing in boiling point by means of distillation, typically using a fractionating column

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14
Q

What determines what fraction a molecule will go into?

A

The size and length of the hydrocarbon

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15
Q

Explain how the fractional distillation of crude oil works

A

The different hydrocarbons in crude oil have different boiling points, due to the differing chain lengths. This allows the hydrocarbons to be grouped into fractions of a similar boiling point, allowing for the separation of them

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16
Q

What is natural gas used for?

A

Domestic heating and cooking

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17
Q

What is petrol used for?

A

Fuels for cars

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18
Q

What is kerosene used for?

A

Jet fuel

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19
Q

What is diesel used for?

A

Fuel for some cars and trains

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20
Q

What is fuel oil used for?

A

Ships and power stations

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21
Q

What is bitumen used for?

A

Surfacing roads and roofs

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22
Q

What is common in each fraction

A
  • similar properties
  • similar boiling points
  • similar chain lengths of hydrocarbons
23
Q

Define viscosity

A

Refers to the ease of the flow of a liquid

24
Q

Why does the boiling point increase as the chain length increases?

A

As the molecules get larger, the intermolecular forces of attraction between the molecules becomes greater as there is more surface area in contact between them. This means more heat is required to separate the molecules, leading to an increase in boiling point

25
Q

Why does the viscosity increase with chain length?

A

Due to intermolecular forces of attraction increasing as the molecular size increases

26
Q

Why does the ease of ignition decrease as the chain length increases?

A

As the molecule size increases, they become harder to ignite as more energy is needed to do so, and therefore the smaller molecules are more flammable

27
Q

Explain why the properties of different fractions differ

A

Due to the chain length

28
Q

Describe the main features of a homologous series

A
  • same general formula
  • difference between one molecular formula and the next is CH2
  • graduation in their physical properties
  • same functional group
  • similar chemical group
29
Q

Why do alkanes form a homologous series?

A

They have the same general formula and the same functional group, which also means that they differ by CH2 each time

30
Q

Describe the complete combustion of a hydrocarbon

A

Reaction in which:
- only carbon dioxide and water are produced
- energy is given out

31
Q

When does incomplete combustion occur?

A

When there is a limited supply of oxygen

32
Q

What happens during the incomplete combustion of a hydrocarbon?

A
  • water is produced
  • energy is given out
  • carbon monoxide and soot are produced
33
Q

State the names of some fossil fuels

A
  • coal
  • oil
  • natural gas
34
Q

What is the main hydrocarbon found in crude oil?

A

Alkanes

35
Q

Why is carbon monoxide a toxic gas?

A
  • it combines with the haemoglobin in red blood cells
  • which prevents oxygen from combining
  • this reduces the amount of oxygen carried in the bloodstream
  • causing suffocation and even death
36
Q

What gases are released through the burning of fossil fuels?

A
  • carbon monoxide
  • oxides of nitrogen
  • carbon dioxide
  • sulfur dioxide
37
Q

What causes acid rain?

A

Sulfur and nitrogen oxides

38
Q

Describe the effects of acid rain

A
  • causes corrosion to metal structures, buildings and stattues made of carbonate rocks
  • crops do not grow if soil is too acidic
  • excess acidity in rivers and lakes prevents fish eggs from hatching, and it can kill fish and insects
39
Q

How is sulfur dioxide formed?

A
  • part of hydrocarbon fuels as impurities, such as petrol and diesel
  • release when burnt
40
Q

How does sulfur dioxide cause acid rain?

A
  • sulfur dioxide formed from combustion dissolves in rainwater droplets to form sulfuric acid
  • which then falls with rainwater
41
Q

How are oxides of nitrogen produced?

A

Formed when nitrogen and oxygen react at high temperatures in internal combustion engines and blast furnaces

42
Q

How do oxides of nitrogen cause acid rain?

A
  • Nitrogen dioxide reacts with rain water to form a mixture of nitrous and nitric acids
  • which contribute to acid rain
  • when droplets containing these acids are heavy enough, they will fall as acid rain
43
Q

What are installed in cars to prevent the formation of nitrogen oxides?

A

Catalytic convertors

44
Q

What is an alternative fuel we can use instead of petrol and diesel?

A

Hydrogen fuel

45
Q

What are the advantages of using hydrogen fuel?

A
  • releases more energy per kg as compared to other fuels
  • does not pollute as it only produces water on combustion, no other product is formed
46
Q

What are the disadvantages of using hydrogen fuel?

A
  • expensive and requires energy for the production process
  • difficult and dangerous to store as it is stored in highly pressurised containers
47
Q

Define cracking

A

Involves breaking covalent bonds in hydrocarbon molecules

48
Q

What are the two types of cracking?

A

Catalytic cracking and thermal cracking

49
Q

How is cataylitic cracking carried out?

A
  • crude oil fractions are heated to evaporate them
  • vapours are passed over a catalyst containing aluminium oxides
  • this breaks the covalent bonds when they come into contact with the surface of the catalyst, causing thermal decomposition reactions
  • this produces a random selection of alkanes and alkenes
50
Q

How is steam/thermal cracking carried out?

A
  • process carried out similar to catalytic cracking, but at higher temperatures
  • vapourised hydrocarbons are mixed with steam and heated to a high temperature, which induces cracking
51
Q

Why is cracking necessary?

A

The demand for certain fractions of crude oil is higher than its supply, so therefore we must convert the surplus unwanted fractions into more useful ones to supply the demand

52
Q

Is cracking an endothermic or exothermic reaction?

A

Endothermic

53
Q

What are the two hydrocarbons formed by cracking?

A

An alkane and an alkene

54
Q

What is the difference between a saturated and an unsaturated bond?

A
  • saturated: single bonds between the carbon atoms eg: alkanes
  • unsaturated: form double bonds between the carbon atoms

GCSE Edexcel Separate Chemistry (27 decks)

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