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Chemistry Daisy > Fuels And Earth Science > Flashcards

Fuels And Earth Science Flashcards

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1
Q

Hydrocarbon

A

Is a molecule that contains Hydrogen and carbon only

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2
Q

What industry are hydrocarbons used in?

A

They are important in the petrochemical industry and used as fuels. - scientist who work with chemicals from fuels

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3
Q

What is the homologous Series?

A

A family of molecules which have the same general formula and share similar chemical properties

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4
Q

What is crude oil?

A

A complex mixture of lots of different hydrocarbons which contain just carbon and hydrogen

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5
Q

What is a fuel?

A

Something that can be burned to release heat and light energy

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6
Q

What is fractional distillation?

A

The process where chemists separate the crude oil mixture into more useful fractions with similar boiling points

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7
Q

What is gas used for?
Short or long chain?
High or low boiling point
Ignition?

A 
Used in domestic heating and cooking 
-short chain
-top of the fractionating column  
Low boiling point 
High ignition
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8
Q

What is petrol used for?
Short or long chain?
High or low boiling point
Ignition?

A

Used as a fuel in cars
-short chain
Low boiling point
High ignition

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9
Q

What is kerosene used for?
Low or high boiling point
Ignition

A

Used as fuel in aircraft
Low boiling point
High ignition

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10
Q

What is diesel used for?
Chain size?
Boiling point?
Ignition?

A

Used as a fuel in some cars and larger vehicles- trains or lorries
Moderate size chain
High boiling point
Low ignition

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11
Q

What is fuel oil used for?
-high or low boiling point
Chain size?
Ignition?

A

Used as a fuel for large ships and also in some power stations
High boiling point
Low ignition
Long chain

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12
Q

What is bitumen used for?
-short or long chain?
High or low boiling point
Ignition

A

Used to surface roads and roofs
Long chain
Very high boiling points
Low ignition

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13
Q

2 differences between simple and fractional distillation

A

SD - cheap and easy equipment needed
FD-expensive and complicated
SD- can only separate mixtures of two substances
FD- can separate mixtures of two or more substances

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14
Q

Intermolecular forces in hydrocarbons

A

Intermolecular forces of attraction break a lot more easily in small molecules than bigger molecules- forces are much stronger in bigger molecules
-big chains have higher molecules than small chains

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15
Q

Why are shorter hydrocarbons easier to ignite?

A

Because they have a lower boiling point which tends to be a gas at room temp
Gas molecules mix with oxygen in the air to produce a gas mixture which bursts into flames if it come into contact with a spark

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16
Q

Viscosity

A

Measures how easily a substance flows

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17
Q

What is the viscosity of long chain hydrocarbons?

A

They have a higher viscosity as the stringer the force between hydrocarbon molecules, the harder it is for the liquid to flow

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18
Q

What is the viscosity of shorter hydrocarbons?

A

Low viscosity so they are much runnier

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19
Q

Why do hydrocarbons make great fuels?

A

Because the combustion reactions that happen when you burn them in oxygen give out lots of energy as the reaction is very exothermic

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20
Q

Complete combustion

A

When you burn hydrocarbons with plenty of oxygen, the only products are carbon dioxide and water

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21
Q

Incomplete combustion

A

Occurs when a hydrocarbon burns a limited supply of oxygen

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22
Q

Rules for Alkanes

  • how many bonds do carbon make?
  • how many bonds do hydrogen make?
A

Made of hydrogen and carbon only
Carbon atoms will make 4 bonds
Hydrogen atoms will make 1 bond
Alkanes contain only carbon single bonds- they are a saturated compounds

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23
Q

What does saturated mean?

A

A saturated substance is one in which the atoms are linked by single bonds.

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24
Q

What does unsaturated mean?

A

unsaturated means a molecule contains double or triple carbon-carbon bonds.

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25
Q

What is the general formula for Alkanes?

A

2n + 2

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26
Q

What is the equation for complete combustion?

A

Petrol + oxygen —carbon dioxide + water

27
Q

What does incomplete combustion produce?

A

Carbon dioxide
Water
Carbon Manoxide
Soot

28
Q

Why is carbon manoxide bad?

A

It can combine with the red blood cells and stop your blood from doing its proper job of carrying oxygen around the body.

29
Q

What can a lack of oxygen cause?

A

A lack of oxygen in the blood supply to the brain can lead to fainting , a coma or even death

30
Q

What dust is made during incomplete combustion?

A

Tiny particles of carbon can be released into the atmosphere. When they fall back to the ground, they deposit themselves as soot.

31
Q

Why is soot bad?

A

It makes building look dirty, reduces air quality and can cause respiratory problems

32
Q

Incomplete combustion

A

Happens when there is a limited supply of oxygen

33
Q

What do low levels of oxygen mean in incomplete combustion?

A

Hydrogen and carbon atoms in the fuels can only be partially oxidised

34
Q

When you burn a fossil fuel, what is released?

A

Carbon Dioxide
Sulphur dioxide
Nitrogen oxides

35
Q

Why is sulphur dioxide bad?

A

When it mixes with clouds, it forms dilute sulfruic acid- which falls as acid rain
Acid rain cause lakes to become acidic - killing plants and fish
It also kills trees, damages limestone buildings and make metal corrode

36
Q

How are nitrogen oxides created?

A

Created from a reaction between the nitrogen and oxygen in the air, caused by the energy released in combustion reactions.

37
Q

Why are nitrogen oxides bad?

A

They can contribute to acid rain and can cause photochemical smog.

38
Q

What are some pros of hydrogen gas?

A

It is very clean
Only waste product is water
It’s obtained from water - not going to run out

39
Q

What are the cons of hydrogen gas?

A

You need a special and expensive engine

It’s hard to store and is not widely available

40
Q

What is cracking?

A

It turns long saturated molecules into smaller unsaturated and Alkane molecules which are more useful.

41
Q

What is cracking a form of?

A

Thermal decomposition
This where one substance breaks down into at least two new one when you heat it. This means breaking strong covalent bonds which needs lots of energy

42
Q

Why do we do cracking?

A

There is more demand for smaller molecules like petrol, diesel than for Bitumen and fuel oil

43
Q

What is the process of cracking?

A

Really viscous crude oil fractions are heated
Under high temps of 650c the fractions evaporate
These vapours are passed over a catalyst -aluminium oxide
They produce the desired smaller chains
Each cycle produces a saturated alkane and an unsaturated Alkene

44
Q

General formula for alkenes

A

CnH2n

Hydrogen is double carbon

45
Q

What makes a good fuel?

A

Affordable. Clean. Easy to transport

Available. Renewable. Safe. Efficient.

46
Q

Advantages of fossil fuels

A

Very large amounts of electricity can be generated in one place
Transporting oil and gas is easy
Gas fired power is very efficient

47
Q

Disadvantages of fossil fuels

A

Burning fossil fuels produce carbon dioxide - contributes to green house gases
Mining coal can be dangerous and difficult
Fossil fuels are non renewable

48
Q

What was the Earth like at first?

Phase 1

A

The surface was molten
No atmosphere
Covered in volcanoes- releasing carbon dioxide, steam, methane and ammonia
After - atmosphere was mostly carbon dioxide - water vapour condensed to form oceans

49
Q

What happened to the earth in phase 2?

A

Lots of carbon dioxide dissolved in oceans

Nitrogen gas was put into atmosphere- created by ammonia and oxygen reacting and was released by denitrifying bacteria

50
Q

What happened to the earth in phase 2 part 2?

A

Green plant evolved - as they photosynthesised, they removed carbon dioxide and produce oxygen
Much of the carbon dioxide got locked up in fossil fuels and sedimentary rocks

51
Q

What happened to the Earth in phase 3?

A

Build up of oxygen allows more complex organisms to evolve
Oxygen also created the ozone layer which blocked harmful rays from the sun and enabled even more complex organisms to evolve

52
Q

Why does an increase in the human population affect levels of atmospheric carbon dioxide?

A

More people respiring - more co2
More energy needed for living
More countries are becoming industrialised - energy demand will increase
More space is need - cutting down trees

53
Q

How does deforestation affect the levels of carbon dioxide in the air?

A

As they photosynthesise they take in carbon dioxide- fewer plants means less carbon dioxide is taken out of the atmosphere

54
Q

What are greenhouse gases

A

The gases in the atmosphere that can absorb and reflect heat radiation - carbon dioxide, water vapour , methane

55
Q

What is the enhanced greenhouse effect?

A

If the concentration of greenhouse gases in the atmosphere increases you get an enhanced greenhouse effect. This is where the most heat radiation from the earth is absorbed and less is re emitted back into space - cause the atmosphere to heat up.

56
Q

Greenhouse effect 1

A

The earth radiates some of the heat radiation it absorbs as longer wavelength infrared

57
Q

Greenhouse effect 2

A

Some of the infrared radiation is absorbed by greenhouse gases

58
Q

Greenhouse effect 3

A

Some of the radiation is reflected back to Earth by the greenhouse gases

59
Q

Greenhouse effect 4

A

Some infrared radiation is re emitted back into space

60
Q

Greenhouse effect 5

A

The absorption and reflection of the infrared radiation by greenhouse gases is what keeps the earth warm

61
Q

What is global warming

A

The increase in the earths average surface temperature due to rising levels of greenhouse gases

62
Q

What is climate change?

A

A long term change in the earths climate

63
Q

What are the 4 ways that cause climate change?

A

Burning fossil fuels
Intensive livestock farming - methane forms cows
Deforestation
Intensive rice paddy farming - methane and carbon dioxide

64
Q

What are the impacts of climate change?

A 
Destroying habitats 
Extreme weather 
Sea levels rising 
Droughts 
Extinction

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