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GCSE Chemistry > Chapter 9 - Crude oil and fuels > Flashcards

Chapter 9 - Crude oil and fuels Flashcards

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1
Q

Define crude oil

A

A finite resource found in rocks. It is a mixture of different hydrocarbons of different chain lengths.

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2
Q

How was crude oil formed (simple)?

A

From the remains of ancient biomass consisting of mainly plankton, which was compressed and buried by mud.

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3
Q

Where can crude oil be found?

A
  • In vast underground reservoirs where ancient seas were located.
  • In tiny spaces in sedimentary rocks
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4
Q

What is a hydrocarbon?

A

A compound consisting only of carbon and hydrogen atoms.

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5
Q

Crude oil is a mixture, what does this tell us about the method at which it can be separated?

A
  • Mixtures are made up of substances that are not chemically bonded together.
  • Therefore, crude oil is a mixture (of hydrocarbons) so it can be separated using physical separation techniques.
  • This includes fractional distillation.
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6
Q

Crude oil is a non-renewable fossil fuel, what does this mean?

A
  • It is finite - as it eventually runs out given that it takes millions of years to form. So it can be described as non-renewable.
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7
Q

What is the main homologous series of hydrocarbons in crude oil?

A

Alkanes.

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8
Q

Define homologous series.

A

A series consisting of compounds with the same functional group, similar chemical properties and can be represented by the same general formula.

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9
Q

What is the general formula for alkanes?

A

CnH2n+2

(remember the subscripts are small)

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10
Q

What are the first 4 alkanes?

A
  • Methane (CH4)
  • Ethane (C2H6)
  • Propane ( C3H8)
  • Butane (C4H10)
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11
Q

Alkanes are saturated compounds, what does this mean?

A
  • When a compound is saturated, it only consists of single bonds.

So, in alkanes, all carbon-carbon bonds are single and covalent.

This means each carbon atom is bonded to the max. amount of hydrogen atoms as possible; no more H+ atoms can be added.

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12
Q

Define alkane.

A
  • A homologous series of hydrocarbons, where each carbon-carbon bond is single and covalent.
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13
Q

When describing the properties of hydrocarbons, what are the 4 you should mention?

A
  • Viscosity: (the measure of a fluid’s resistance to flow)
  • Boiling point: (temp a gas condenses or a liquid evaporates)
  • Volatility: (Tendency for a fluid to turn into a gas/evaporate)
  • Flammability: (how easily a substance (ITC fluid.) burns/combusts).
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14
Q

Describe the trend in the properties of hydrocarbons.

A
  • Boiling point increases as carbon chain length increases.
  • Viscosity increases as carbon chain length increases.
  • Flammability decreases as carbon chain length increases.
  • Volatility decreases as carbon chain length increases.

*This makes hydrocarbons with shorter chain lengths more useful as they have a lower boiling point (resulting in higher volatility and flammability).

*This means they ignite and burn more easily than longer carbon chain lengths.

*Meaning they produce more energy more easily with less smoky/toxic flames

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15
Q

True or false, we can crack hydrocarbons with longer chain lengths to make shorter ones?

A

True.

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16
Q

How can crude oil be separated?

A

Through fractional distillation.

This is where we separate hydrocarbons of different chain lengths according to their boiling points into fractions, so they can be used for different things.

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17
Q

What is a fraction?

A

A quantity collected from a fractionating column consisting of hydrocarbons of similar chain lengths.

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18
Q

Describe the process of fractional distillation.

A
  • Crude oil is heated evaporated and fed into the bottom of the fractionating column as vapour.
  • The fractionating column is kept hotter at the bottom and cooler at the top, so temp. increases as you go down.
  • The vapours rise rapidly up frac. column through bubble caps and condense at their boiling points.
  • This is collected in fractions which contain hydrocarbons of similar chain length, and removed.
  • Fractions are collected in a continuous process.
  • Hydrocarbons w very long carbon chain lengths have a higher boiling point so is collected from the bottom and condense to form thick liquids or solids at room temperature.
  • Hydrocarbons w shorter carbon chain lengths have a lower boiling point and are collected as gases from the top of the column as they don’t condense.
  • Once collected, fractions are processed before use.
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19
Q

Uses of each fraction (from bottom to top).

A
  • Bitumen (long HC chains removed as residue) used for ROADS AND ROOFS.
  • Fuel oil (petrol, gas oil) - used to fuel cars, ships and power stations
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20
Q

Use of Bitumen.

A

(long hydrocarbon chains removed as residue).

  • Used for roads and roofs.
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21
Q

What is the use of fuel oils such as petrol and gas oil.

A

Used to fuel ships and power stations.

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22
Q

Use of Diesel.

A

Used to fuel cars, buses and lorries.

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23
Q

Use of kerosene.

A

Used to fuel aircrafts.

24
Q

Use of gasoline.

A

Fuel for cars.

25
Q

Use of refinery gases such as LPG.

A

(Short chains, typically alkanes)

used as fuel for camping stoves.

26
Q

study this diagram.

A

https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.savemyexams.com%2Fgcse%2Fchemistry%2Faqa%2F18%2Frevision-notes%2F7-organic-chemistry%2F7-1-hydrocarbons-fuel–feedstock%2F7-1-2-fractional-distillation–petrochemicals%2F&psig=AOvVaw1F6xHUEC-S03LQL0_9ojgN&ust=1695638489147000&source=images&cd=vfe&opi=89978449&ved=0CA8QjhxqFwoTCPib2-CHw4EDFQAAAAAdAAAAABAD

27
Q

Some fractions can be used as feedstock in the petrochemical industry.

What is feedstock?

A
  • Feedstock is a raw material/chemical used to make other chemicals.

e.g of feedstock = crude oil (input/fed - output).

28
Q

What are some products of feedstock fractions?

A
  • Solvents.
  • Polymers.
  • Detergents.
  • Lubricants.
29
Q

Why are hydrocarbons combusted?

A

To be used as fuels, as they produce energy.

30
Q

During combustion of Hydrocarbons, what can we say happens to the Hydrogen and oxygen atoms?

A

They are oxidised.

31
Q

What is complete combustion?

A

Combustion that occurs when there is an unlimited supply of oxygen so it produces carbon dioxide and water.

32
Q

What are the products of complete combustion?

A

Carbon dioxide and water

33
Q

In combustion reactions, a reactant is always?..

A

Oxygen.

34
Q

How can we test complete combustion?

A
  • By testing for water (cobalt chloride paper and anhydrous copper sulphate) and carbon dioxide (limewater).
35
Q

What is the positive test for water in anhydrous copper sulphate powder?

A

Anhydrous copper sulphate powder:

  • Without water - WHITE
  • With water - BLUE
36
Q

What is the positive test for water cobalt chloride paper?

A

Cobalt chloride paper:

  • Without water - BLUE
  • With water - PINK
37
Q

What is the positive test for carbon dioxide in limewater?

A

Limewater:

  • Without carbon dioxide - COLOURLESS
  • With carbon dioxide - CLOUDY
38
Q

Incomplete combustion occurs when?..

A

There is a limited amount of oxygen to oxidise hydrogen and carbon so it produces either carbon monoxide and water or carbon monoxide and carbon.

39
Q

What are the products of incomplete combustion?

A

Carbon monoxide (CO) and Carbon (C).

OR

Carbon monoxide and water.

40
Q

Why is incomplete combustion dangerous?

A

It produces carbon monoxide.

41
Q

Why is carbon monoxide dangerous/toxic?

A
  • It is toxic, odourless and colourless.
  • In the body it binds to haemoglobin in red blood cells.
    *This prevents haemoglobin from carrying oxygen and transporting it around the body to diff organs, and prevents it from carrying it carbon dioxide to the lungs for excretion.
42
Q

Alkane + Oxygen -> Carbon monoxide + Water or Carbon

Is an example of?

A

Incomplete combustion.

43
Q

Alkane + Oxygen -> Carbon dioxide + water

Is an example of?

A

Complete combustion.

44
Q

What is cracking?

A

The process by which larger hydrocarbon molecules are broken down into smaller and more useful ones through thermal decomposition such as catalytic cracking and steam/thermal cracking.

45
Q

Why do we crack longer HC chains into smaller ones?

A
  • Longer HC chains are less useful because they have a higher boiling point due to their stronger IM forces.
  • So they are less volatile and flammable and ignite less easily.
  • So they require a lot of energy to be broken down.
  • They also produce smokey flames.
  • This makes them bad fuels.

WHILE…

  • Shorter HC chains are make more useful fuels so are more in demand.
  • This is bc they have weaker IM forces so require less energy to be broken.
  • So, they are more volatile and flammable than Larger HC chains, and ignite more easily.
  • They also produce less smokey flames.
  • This makes them good fuels.

Because smaller HC chains are so in demand, there sometimes isn’t enough, so they longer ones are cracked to make smaller and more useful ones.

46
Q

State 2 methods of cracking:

A
  • Catalytic cracking.
  • Steam cracking.
47
Q

What are the conditions for catalytic cracking?

A

Hight temp (500 degrees C) and Catalyst present.

48
Q

Explain what happens during catalytic cracking.

A
  • Long HC chain is heated and vaporised.
  • It is passed over a hot catalyst e.g Aluminium oxide.
  • This breaks down the covalent bonds in large HC molecule randomly, to produce a mixture of smaller alkenes and alkanes.
  • This is an example of a thermal decomposition reaction.
49
Q

Explain what happens during steam/thermal cracking.

A
  • Long HC chain is heated and vaporised.
  • It is mixed with steam which induces the breaking of covalent bonds and therefore results in cracking into a mixture of smaller and more useful alkenes and alkanes.
50
Q

State the products of cracking.

A

SMALLER, alkenes and alkanes.

51
Q

What is an alkene?

A

A homologous series of unsaturated hydrocarbons consisting of covalent bonds and at least one double bond.

52
Q

What is the temp required for catalytic cracking?

A

500 degrees C.

53
Q

The general formula for alkenes is?

A

CnH2n (subscribes are small)

54
Q

How do we test for the presence of alkenes?

A

Using Bromine water.

Bromine is orange, but alkene decolourises it.

55
Q

True or False, alkenes burn in air?

A

True, but not as well as small alkanes.

56
Q

Why do alkanes not react with bromine water, or anything?

A

Because they are saturated.

GCSE Chemistry (13 decks)

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