Chemistry - Crude oil, fuels and organic chemistry

Question 1

What is crude oil?

Answer 1

-Crude oil is a mixture of hydrocarbons which can be separated using fractional distillation.
-It is produced from the remains of dead marine animals and plants that lived around 300 million years ago. When the remains sank to the bottom of the sea, they were covered by sand and other sediments. Layer upon layer of sediments built up over time and pressure and heat caused the remains to break down, forming crude oil

Question 2

What does fractional distillation do?

Answer 2

Fractional distillation separates a mixture into a number of different parts, called fractions. A fraction of crude oil is a mixture of chemicals in the crude oil that have similar boiling points.

Question 3

How does fractioning column work?

Answer 3

A tall fractionating column is fitted above the mixture, with several condensers coming off at different heights. The column is hot at the bottom and cool at the top. Substances with high boiling points condense at the bottom and substances with lower boiling points condense on the way to the top.
The crude oil is evaporated inside a furnace before entering the fractionating column where its vapours condense at different temperatures.

Question 4

What are the properties of the large molecules at the bottom of the fractioning column?

Answer 4

High boiling point
Do not flow easily
Do not ignite easily
Not very volatile
Long chain length

Question 5

What are the properties of the small molecules at the top of the fractioning column?

Answer 5

Low boiling point
flow easily
ignite easily
very volatile
shorter chain lenghts

Question 6

What properties do hydrocarbons have as you go up the fractioning column?

Answer 6

As you go up the fractioning column:
-smaller chain lengths
-lower boiling points
-more volatility (easy to evaporate)
-higher flammability
-lighter colour (the bottom is black, the middle fractions are brown/yellow and the top is colourless)

Question 7

What are other fossil fuels?

Answer 7

Natural gas - mainly consists of methane. It is used in domestic boilers, cookers and Bunsen burners, as well as in some power stations.
Coal - was formed from the remains of ancient forests. It can be burned in power stations. Coal is mainly carbon but it may also contain sulfur compounds, which produce sulfur dioxide when the coal is burned. This gas is a cause of acid rain.

Question 8

What is the importance of crude oil?

Answer 8

• The price of crude oil is controlled by oil companies, which means they have a great deal of influence on the global economy
• Countries that produce oil for other countries hold a great deal of political power as they can essentially ‘cut off’ other countries from the crude oil supply over any political disagreements.
• War or a political crisis in an oil-producing country can restrict crude oil supplies, which can have a major impact on the global economy.

Question 9

What are the issues of crude oil?

Answer 9

• Burning fossil fuels releases carbon dioxide into the atmosphere.
• Oil spillages can have a disastrous effect on the local environment, killing off thousands of animals such as fish and sea birds, and require a great deal of effort to clean up.
• Oil refineries and oil-fired power stations take up a lot of land and so destroy potential wildlife habitats and spoil the countryside.

Question 10

What is the purpose of cracking?

Answer 10

Cracking allows large hydrocarbon molecules to be broken down into smaller, more useful hydrocarbon molecules.

Question 11

What is the process of cracking?

Answer 11

-Fractions containing large hydrocarbon molecules are heated to vaporise them. They are then:
-heated to 600-700°C
-passed over a catalyst of silica or alumina
-These processes break covalent bonds in the molecules, causing thermal decomposition reactions. Cracking produces smaller alkanes and alkenes.

Question 12

Why is there a greater demand for smaller hydrocarbons?

Answer 12

-Some of the smaller hydrocarbons formed by cracking (octane) are used as fuels
-Alkenes are used to make polymers in the manufacturing of plastics.

Question 13

What are hydrocarbons?

Answer 13

compounds of hydrogen and carbon only

Question 14

What happens when hydrocarbons burn?

Answer 14

-the carbon oxidises to carbon dioxide
-the hydrogen oxidises to water

Question 15

What are the three things required for a fire to burn?

Answer 15

oxygen
heat
fuel

Question 16

How can oxygen be removed from a fire?

Answer 16

• carbon dioxide extinguisher - The carbon dioxide extinguisher pushes oxygen away from the fire and replaces it with carbon dioxide, which is non-flammable and more dense than air.
• fire blanket - Fire blankets form a seal around the fire and prevent more oxygen from reaching the fire.

Question 17

How can heat be removed from a fire?

Answer 17

• Water - absorbs the heat from a fire very effectively.
• blowing out a flame - Blowing out the flame on a candle is a good example of this. The fast moving air removes the heat from the candle, stopping it from burning any more.

Question 18

How can fuel be removed from a fire?

Answer 18

• Fire resistant materials - any fire will not have an adequate fuel source to keep burning and so this is a very effective method of fire prevention.

Question 19

What is the calorimetry method?

Answer 19

1)Cold water is measured into a copper calorimeter – a small metal can.
2)The starting temperature of the water is recorded.
3)The water is heated using the flame from the burning fuel.
4)The final temperature of the water is recorded.
a simple calorimetry experiment to measure the heat energy released from burning fuel

Question 20

How do you ensure a fair test for calorimetry?

Answer 20

Several variables should be kept constant:
-the volume of water used
-the starting temperature of the water
-the temperature increase
-the distance of the flame from the calorimeter

Question 21

Why isn’t hydrogen being used for fuels?

Answer 21

-It is highly flammable so is more dangerous.
-Most hydrogen is obtained from fossil fuels, so carbon dioxide is still released during the overall process.
-It can be formed from electrolysis but this uses a lot of energy.

Question 22

What temperature should liquid hydrogen be stored at?

Answer 22

• -250C

Question 23

What are alkanes?

Answer 23

The alkanes are a homologous series of hydrocarbons. This means that they have similar chemical properties to each other and they have trends in physical properties. Alkanes are saturated hydrocarbons consisting of single bonds only

Question 24

What is the formula for alkanes?

Answer 24

C(n) H(2n+2)

Question 25

What are saturated hydrocarbons?

Answer 25

Alkanes are saturated hydrocarbons. This means that their carbon atoms are joined to each other by single bonds. This makes them relatively unreactive, apart from their reaction with oxygen in the air – which we call burning or combustion.

Question 26

What is isomerism?

Answer 26

This means that their atoms can be arranged differently to make slightly different compounds with different properties.

Question 27

What are alkenes?

Answer 27

Alkenes are a homologous series of hydrocarbons that contain a carbon-carbon double bond. The number of hydrogen atoms in an alkene is double the number of carbon atoms

Question 28

What is the formula for alkenes?

Answer 28

C(n) H(2n)

Question 29

What are unsaturated hydrocarbons?

Answer 29

Alkenes are unsaturated, meaning they contain a double bond. This bond is why the alkenes are more reactive than the alkanes.

Question 30

What is the test for alkanes and alkenes?

Answer 30

1) Alkene and alkane are added into bromide solution in separate test tubes
2)Both are shaken
3)The alkane shows no change - The alkene decolourises.
The presence of the C=C double bond allows alkenes to react in ways that alkanes cannot. This allows us to distinguish alkenes from alkanes using a simple chemical test.

Question 31

What is an addition reaction?

Answer 31

The reaction between bromine and alkenes is an example of a type of reaction called an addition reaction. The bromine is decolourised because a colourless dibromo compound forms.

Question 32

What are the prefixes for the amount of carbons in an alkane?

Answer 32

1-Meth(ane)
2-Eth(ane)
3-Prop(ane)
4-But(ane)
5-Pent(ane)

Question 33

What are polymers?

Answer 33

Polymers are very large molecules made when many smaller, reactive molecules join together, end to end. The smaller molecules are called monomers.

Question 34

What is a repeat unit?

Answer 34

A part of a polymer that would make a complete polymer molecule if many of them were joined end to end.

Question 35

What is the use and property of poly(ethene)?

Answer 35

Use - Plastic bags
Property - Low density, waterproof

Question 36

What is the use and property of poly(propene)?

Answer 36

Use - Ropes
Property - Strong, colourful

Question 37

What is the use and property of poly(tetrafluoroethene) – PTFE?

Answer 37

use - Coating for frying pans
Property - Non-stick

Question 38

What is the use and property of poly(chloroethene) – PVC?

Answer 38

Use - Water pipes
Property - Low density, does not corrode

Question 39

What can modern polymers be used for?

Answer 39

-new packaging materials
-waterproof coatings for fabrics (eg for outdoor clothing)
-fillings for teeth
-dressings for cuts
-hydrogels (eg for soft contact lenses and disposable nappy liners)
-smart materials (eg shape memory polymers for shrink-wrap packaging)

Question 40

What are the environmental issues with polymers?

Answer 40

-Most polymers are very unreactive and are non-biodegradable, ie they do not rot because microbes cannot break them down.

-If polymers are put in normal household waste, they are then taken to landfill and buried, where they will remain for hundreds of years.

-Burning plastics as fuel is not a good solution either, as this leads to the release of carbon dioxide (contributing to the greenhouse effect) as well as various toxic gases.

Question 41

What are the advantages of recycling plastic?

Answer 41

• Less plastic goes to landfill, reducing pollution and making current landfill sites last longer.
• Less crude oil is needed to produce new plastics. This conserves crude oil which is a finite resource that will eventually run out.
• Recycling plastic requires less energy than making new plastic. This lowers costs and reduces greenhouse gas emissions.

Question 42

What is the formula for alcohols?

Answer 42

C(n) H(2n + 1) OH

Question 43

What functional group do all alcohols have?

Answer 43

They all contain the functional group –OH, which is responsible for the properties of alcohols.

Question 44

What are the first three alcohols in the homologous series used for?

Answer 44

-They are highly flammable, making them useful as fuels.
-They are also used as solvents in marker pens, medicines, and cosmetics (such as deodorants and perfumes).

Question 45

What do ethanol molecules contain?

Answer 45

Ethanol molecules contain carbon, hydrogen and oxygen atoms.

Question 46

How is ethanol made?

Answer 46

-sugar (glucose) from plant material is converted into ethanol and carbon dioxide. This typically takes place at temperatures of around 30°C.

-The enzymes found in single-celled fungi (yeast) are the natural catalysts that can make this process happen

Question 47

What are the uses of ethanol?

Answer 47

• Alcoholic drinks
• an extremely good solvent
• the active ingredient in anti-bacterial hand cleansers, that do not require water
• used as a fuel

Question 48

What are biofuels?

Answer 48

-Biofuels are produced from natural products, often plant biomass containing carbohydrate. As biofuels are produced from plants, they are renewable and theoretically carbon neutral.
-Some biofuels are produced by using microorganisms to anaerobically ferment carbohydrate in the plant material

Question 49

What is bioethanol?

Answer 49

Bioethanol is an alcohol made from plants containing sugar - Sugar cane, Maize. It is a renewable source.

Question 50

What are the disadvantages of bio ethanol?

Answer 50

• The demand for biofuel crops means greater demand on rainforest land.
• Crops grow slowly in parts of the world that have lower light levels and temperatures, so growing biofuel crops in these countries would not satisfy the demand for fuel.
• For bioethanol to be burnt in a car engine, some engine modification is needed. Modern petrol engines can use petrol containing up to ten per cent ethanol without needing any modifications, and most petrol sold in the UK contains ethanol.
• Some people morally object to using food crops to produce fuels. For example, it could cause food shortages or increases in food prices.

Question 51

How do you test for alcohols?

Answer 51

When alcohols are gently heated with a mixture of potassium dichromate(VI) and sulfuric acid, the mixture changes colour from orange to green. This chemical test was originally used to test for the presence of alcohol on people’s breath if they were suspected of drink-driving.