C9

Question 1

What is a hydrocarbon?

Answer 1

Any compound that is formed from carbon and hydrogen atoms only .

Question 2

What are alkanes?

Answer 2

• Simplest type of hydrocarbon
• a homologous series
• saturated compounds

Question 3

What is the general formula for an alkane?

Answer 3

CnH2n+2

Question 4

What is a homologous series?

Answer 4

A group of organic compounds that react in a similar way

Question 5

Why are alkanes saturated compounds ?

Answer 5

Each carbon atom forms four single covalent bonds

Question 6

What are the first four alkanes?

Answer 6

• methane
• ethane
• propane
• butane

Question 7

How can alkane molecule be represented ?

Answer 7

In a H and C diagram or in an equation

Question 8

How does the length of carbon chain change the properties of the hydrocarbon chain?

Answer 8

• the shorter the carbon chain , the more runny a hydrocarbon is , the less viscous
• hydrocarbons with shorter chains are also more volatile , have lower boiling points
• also shorter carbon chains means they are more flammable

Question 9

What happens in complete combustion of any hydrocarbon in oxygen?

Answer 9

• releases lots of energy
• waste products of water vapour and carbon dioxide
• both carbon and hydrogen from the hydrocarbon are oxidised

Question 10

What are hydrocarbons used for?

Answer 10

Fuels due to the amount of energy released when they combust completely

Question 11

What is crude oil?

Answer 11

Finit resource found in rocks . It is the remains of an ancient biomass consisting mainly of plankton that was buried in the mud

Question 12

What does crude oil mainly consist off?

Answer 12

Hydrocarbons

Question 13

What is crude oils state?

Answer 13

Mixture of compounds

Question 14

What is the equation for the complete combustion of a hydrocarbon?

Answer 14

Hydrocarbon + oxygen —-> carbon dioxide + water

Question 15

What can change depending on the size of the hydrocarbons molecules ?

Answer 15

• boiling point
• viscosity
• flammability

Question 16

What does the flammability , viscosity and boiling determine?

Answer 16

How the hydrocarbon will be used as a fuel

Question 17

How is crude oil separated ?

Answer 17

Fractional distillation

Question 18

How does fractional distillation work?

Answer 18

1. Oil is heated until most has turned to gas. Gas enters fractionating column and liquid bit is drained off
2. in column there is a temperature gradient ( hot at bottom and cooler as you go up)
3. Longer hydrocarbons have high boiling points. They condense back to liquids and drain out of the column early on. The shorter chains have low boiling points and drain out later on, near the top where it is cooler.
4. separated crude oil into fractions . Each fraction contains a mixture of hydrocarbons that contain a similar number of carbon atoms , so similar boiling points

Question 19

What does oil do for us in our daily lives?

Answer 19

Provides fuel for most modern transport . Diesel oil , kerosene, heavy fuel oil and LPG (liquid petroleum gas ) all come from crude oil

Question 20

What is the petrochemical industry?

Answer 20

Use hydrocarbons from crude oil , as feed stock to make new compounds for use in things like polymers, solvents , lubricants and detergents

Question 21

What are the products from crude oil and example off?

Answer 21

Organic compounds. Compounds containing carbon atoms

Question 22

Why do you get such a large variety of products from crude oil?

Answer 22

Can bond together to form different groups called homologous series . These groups contain similar compounds with many properties in common . Alkanes and alkenes are examples of these

Question 23

Why do people want smaller chained hydrocarbon?

Answer 23

Flammable and can make good fuels and are in high demand. Long chains on the other hand are thick gloopy liquids like tar that are not useful

Question 24

How are longer hydrocarbons formed from fractional distillation turned into more useful smaller ones?

Answer 24

Cracking

Question 25

What are the products of cracking used for?

Answer 25

Fuels

Question 26

What does cracking produce?

Answer 26

Alkanes and alkenes

Question 27

What are alkenes?

Answer 27

A lot more reactive alkanes . They are used as a starting material when making other compounds and can be used to make polymers

Question 28

How can you test for alkenes ?

Answer 28

Bromine water. Orange bromine water is added to an alkane , no reaction will happens and it’ll stay bright orange.
If its added to an alkene the bromine reacts with it to make a colourless compound - so bromine water is decolourised

Question 29

What type of reaction is cracking?

Answer 29

Thermal decomposition

Question 30

What is thermal decomposition?

Answer 30

Breaking molecules down by heating them

Question 31

How to catalytic crack ?

Answer 31

• heat long chain hydrocarbon to vaporise them
• then vapour is passed over a hot powdered aluminium oxide catalyst
• the long chain molecules split apart on the surface of the specks of the catalyst

Question 32

What is steam cracking?

Answer 32

Vaporise long chain hydrocarbon , mix them with steam , then heat them to a very high temperature