C7

Question 1

What type of resource is crude oil?

Answer 1

It is a finite resource

Question 2

What is the remains of crude oil?

Answer 2

It is a resource found in rocks,crude oil is the remains of an ancient biomass consisting mainly of plankton that was buried in mud

Question 3

What is crude oil and what is its structure?

Answer 3

• Crude oil is a mixture of a very large number of compounds
• Most of the compounds in crude oil are hydrocarbons, which are molecules made up of hydrogen and carbon atoms only

Question 4

What are most of the hydrocarbons in crude oil are hydrocarbons called?

Answer 4

Alkanes.

Question 5

What is the general formula for the homologous series of alkanes?

Answer 5

C(n)H(2n+2)

N is the number

Question 6

What are the first four members of alkanes?

Answer 6

The first four members of the alkanes are methane, ethane, propane and butane

Question 7

How can alkane molecules can be represented?

Answer 7

Check CGP Page 150

Question 8

Note:

Answer 8

AQA says that students should be able to recognise substances as alkanes given their formulae in these forms

Question 9

Note:

Answer 9

AQA says that students do not need to know the names of specific alkanes other than methane, ethane, propane and butane

Question 10

Whar can you do with hydrocarbons?

Answer 10

The many hydrocarbons in crude oil may be separated into fractions, each of which contains molecules with a similar number of carbon atoms, by fractional distillation

Question 11

How can the fractions be processed?

Answer 11

The fractions can be processed to produce fuels and feedstock for the petrochemical industry

Question 12

State examples of fuels we use in our modern lifestyle produced from crude oil?

Answer 12

Many of the fuels on which we depend for our modern lifestyle, such as petrol, diesel oil, kerosene, heavy fuel oil and liquefied petroleum gases, are produced from crude oil

Question 13

State many useful materials on which modern life depends are produced by the petrochemical industry

Answer 13

Solvents, lubricants, polymers, detergents

Question 14

How do the vast array of natural and synthetic carbon compounds occur

Answer 14

The vast array of natural and synthetic carbon compounds occur due to the ability of carbon atoms to form families of similar compounds

Question 15

How does fractional distillation work in terms of evaporation and condensation?

Answer 15

Heated crude oil enters a tall fractionating column , which is hot at the bottom and gets cooler towards the top. vapours from the oil rise through the column. vapours condense when they become cool enough. liquids are led out of the column at different heights.

Question 16

What do some properties of hydrocarbons depend on?

Answer 16

Some properties of hydrocarbons depend on the size of their molecules, including boiling point, viscosity and flammability. These properties influence how hydrocarbons are used as fuels.

Question 17

How does boiling point change with increasing molecular size?

Answer 17

The larger the molecules, the more surface area to form (weak) bonds with neighbouring molecules, and the more energy needed to make the molecules break free. So the melting and boiling points of simple covalent substances increase as the molecular mass increases.

Question 18

How does viscosity change with increasing molecular size?

Answer 18

The viscosity increases with increasing molecular size. As the length of the carbon chain increases, the more viscous the hydrocarbon will be. A shorter hydrocarbon chain will be more ‘runny’ than a longer hydrocarbon chain.

Question 19

How does flammability change with increasing molecular size?

Answer 19

The flammability decreases with increasing molecular size. As the length of the carbon chain increases, the less flammable the hydrocarbon will be. Longer chain hydrocarbons are more difficult to ignite as compared to shorter chain hydrocarbons.

Question 20

What happens during the combustion of hydrocarbon fuels?

Answer 20

The combustion of hydrocarbon fuels releases energy. During combustion, the carbon and hydrogen in the fuels are oxidised. The complete combustion of a hydrocarbon produces carbon dioxide and water.

Question 21

Note:

Answer 21

AQA says that students should be able to write balanced equations for the complete combustion of hydrocarbons with a given formula.

(Check CGP Page 150)

Question 22

Note:

Answer 22

Knowledge of trends in properties of hydrocarbons is limited to:

• boiling points
• viscosity
• flammability.

Question 23

What can you do with hydrocarbons?

Answer 23

Hydrocarbons can be broken down (cracked) to produce smaller, more useful molecules

Question 24

How can cracking be done with hydrocarbons?

Answer 24

Cracking can be done by various methods including catalytic cracking and steam cracking

Question 25

What are the conditions used for catalytic cracking?

Answer 25

• High temperatures are required for both cracking methods
• Catalytic cracking involves an aluminium oxide catalyst
• The long chain hydrocarbon is turned into a gas, which then passes over a hot, powdered aluminium oxide catalyst at a temperature of about 550°C

Question 26

What are the conditions used for steam cracking?

Answer 26

• Steam cracking simply involves heat and steam. In steam cracking, the long chain hydrocarbon is turned into a gas, then mixed with steam
• At very high temperatures, over 850 °C, and under pressure, the long chain hydrocarbon will split into shorter chain hydrocarbons and lots of small alkenes

Question 27

What do the products of cracking include?

Answer 27

The products of cracking include alkanes and another type of hydrocarbon called alkenes

Question 28

What is more reaction,alkenes or alkanes?

Answer 28

Alkenes are more reactive than alkanes and react with bromine water, which is used as a test for alkenes

Question 29

What is the colour change when bromine water reacts with an alkene?

Answer 29

Bromine water is an orange solution of bromine. It becomes colourless when it is shaken with an alkene

Question 30

How are the products of cracking useful?

Answer 30

There is a high demand for fuels with small molecules and so some of the products of cracking are useful as fuels

Question 31

What are alkenes used to produce?

Answer 31

Alkenes are used to produce polymers and as starting materials for the production of many other chemicals

Question 32

Note:

Answer 32

Students should be able to balance chemical equations as examples of cracking given the formulae of the reactants and products.

(Check CGP Page 150 or 152)

Question 33

Give examples to illustrate the usefulness of cracking

Answer 33

• It helps to match the supply of fractions with the demand for them
• It produces alkenes, which are useful as feedstock for the petrochemical industry

Question 34

Explain how modern life depends on the uses of hydrocarbons

Answer 34

They serve as fuels and lubricants as well as raw materials for the production of plastics, fibres, rubbers, solvents, explosives, and industrial chemicals.

Question 35

Note:

Answer 35

AQA says that students do not need to know the formulae or names of individual alkenes