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Chemistry > Topic 5 - Fuels > Flashcards

Topic 5 - Fuels Flashcards

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1
Q

What are hydrocarbons?

A

Carbons made of carbon and hydrogen atoms only.

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2
Q

What is crude oil?

A

A complex mixture of hydrocarbons, containing molecules in which carbon atoms are in chains or rings. It’s an important source of useful substances (fuels and feedstock for the petrochemical industry) and a finite (will run out) resource.

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3
Q

What is fractional distillation?

A

The process of separating a mixture of liquids with different temperatures into different parts (fractions).

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4
Q

What is a fraction of crude oil?

A

A smaller mixture of hydrocarbons that contain a similar number of carbons which have similar boiling points.

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5
Q

How fractional distillation happens for crude oil?

A

1) Heat crude oil so that it vaporises
2) Pump heated vapours into a fractionating column
3) Fractionating is cooler at the top and hot at the bottom
4) Crude oil rises up the column
5) When they reach cool part of fractionating column it condense.
Boiling point = condensing point, each part has different condensing point so will move off at different points.

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6
Q

What are the different fractions?

A

Gas
Petrol
Kerosene
Diesel oil
Fuel oil
Bitumen

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7
Q

What’s gas used for?

A

Domestic heating and cooking.

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8
Q

What’s petrol used for?

A

Fuel for cars.

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9
Q

What’s kerosene used for?

A

Fuel for aircrafts.

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10
Q

What’s diesel used for?

A

Fuels for some cars and trains.

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11
Q

What’s fuel oil used for?

A

Fuel for large ships and in some power stations.

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12
Q

What’s bitumen used for?

A

Surface roads and roofs.

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13
Q

What are features of the top of the fractionating column?

A

• Shorter carbon chains
• Low boiling point
• Small molecules
• Ignites more easily
• Lower viscosity

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14
Q

What are the features of the bottom of the fractionating column?

A

• Longer carbon chains
• High boiling point
• Higher viscosity
• Doesn’t ignite very easily
• Large molecules

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15
Q

What the the hydrocarbons found in crude oil belong too?

A

A homologous series of chemicals called alkanes.
Alkanes:
• Ane in the name
• Single C-H bonds
• Saturated (fully bonded)

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16
Q

What is the homologous series?

A

Methane - 1 carbon CH4
Ethane - 2 carbons C2H6
Propane - 3 carbons C3H8
Butane - 4 carbons C4H10
Pentane - 5 carbons
A series of compounds which have the same general formula, differ by CH2 in molecular formula from neighbouring compounds, show a gradual variation in physical properties and have similar chemical properties.

17
Q

What is complete combustion?

A

Happens when there is a good supply of oxygen. The products are water and carbon dioxide.
• Blue flame
• More energy released

18
Q

What is incomplete combustion?

A

Happens when there is a limited supply of oxygen. The products are carbon, carbon monoxide and water.
• Yellow flame
• Less energy released
• Produces soot

19
Q

How can you prove carbon dioxide and water are products of combustion?

A

• White powder in flask turns blue if water is present
• Limewater goes cloudy if CO2 is present

20
Q

Why is carbon monoxide dangerous?

A

• Tasteless
• Odourless
• Colourless
• Dense so sinks to the floor
• Nearer where people sleep

21
Q

Why is carbon monoxide toxic?

A

• Bunds with haemoglobin in red blood cells more strongly than oxygen
• Stops oxygen binding
• Stop respiration
• Stops oxygen reaching the brain
• People go unconscious and die

22
Q

How does acid rain form?

A

1) Sulfur impurities in fossil fuels make sulfur dioxide when they burn.
2) When fuels are burnt in engines, Nitrogen in the air reacts with oxygen in a hot engine to form nitrogen oxide.
3) Sulfur dioxide and nitrogen oxide rise into the atmosphere where they dissolve in the water droplets in the clouds to form sulphuric acid and nitric acid which falls as acid rain.

23
Q

What are problems of acid rain?

A

• Kills aquatic life
• Harms forests by damaging trees
• Corrodes stone and metal

24
Q

What are advantages of using hydrogen rather than petrol as a fuel for cars?

A

• Abundant (a lot of it, everywhere)
• The only waste is water (clean)
• More energy - efficient (releases more energy than petrol

25
Q

What are disadvantages of using hydrogen rather than petrol as a fuel for cars?

A

• Difficult to get because it’s locked in compounds that need to be extracted.
• Extracting hydrogen requires a lot of energy and heat which is expensive
• We don’t have hydrogen fuel infrastructure
• Dangerous, explosive if not stored properly
• Difficult to transport and store
• Most hydrogen is made from natural gas (non-renewable)

26
Q

What are non-renewable fossil fuels obtained from crude oil?

A

Petrol
Kerosene
Diesel oil

27
Q

What is a non-renewable fossil fuel found in natural gas?

A

Methane

28
Q

What is cracking?

A

Cracking involves the breaking down of larger saturated hydrocarbon molecules (alkanes) into smaller, more useful ones some of which are unsaturated (Alkenes)

29
Q

What is an alkane?

A

Saturated hydrocarbon, only has single bonds.

30
Q

What is an Alkene?

A

Unsaturated hydrocarbon which contain double bonds used to make plastics.

31
Q

Why crack hydrocarbons?

A

Long chain hydrocarbons are in low demand as they are less useful.
Shorter chain hydrocarbons can be used in the home and cars, and the Alkene can be turned into plastic.

32
Q

What are risks and preventions of cracking hydrocarbons?

A

• Suckback - water will rise up the delivery tube into hot test tube. Remove the delivery tube before turning off the heat.
• Hot test tube can cause burns. Allow to cool before tidying up.
• Heating to rapidly and violently. Gentle heating with blue flame.

33
Q

What is a polymer?

A

A large molecule containing chains of carbon atoms. They are made form joining many smaller Alkenes together.

34
Q

What happens as a polymer length increases?

A

As the polymer length increases so does the melting and boiling point. This is because as the polymer chain length increases there are more intermolecular forces between the polymers, therefore more energy is needed to melt them increasing their melting point. The longer chains also get tangled up with one another.

Chemistry (13 decks)

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