C9

Question 1

What is crude oil made up of?

Answer 1

It is a mixture of many different carbon compounds. Nearly all of the compounds in crude oil are compounds containing only hydrogen and carbon atoms called hydrocarbons.

Question 2

What’s a mixture?

Answer 2

A mixture contains two or more elements or compounds that are not chemically combined together.

Question 3

What’s fractional distillation?

Answer 3

Fractional distillation is a process used to separate a mixture of liquids that have different boiling points.

Question 4

How is crude oil separated?

Answer 4

By fractional distillation.

Question 5

how do you separate crude oil?

Answer 5

• crude oil is heated and fed into the bottom of a fractional column as hot vapour
• The column is hot at the bottom and cooler at the top, so temperature decreases up the column
• The gases move up the column and the hydrocarbons condense when they reach their boiling points
• Different fractions are collected as liquids at different levels in a continuous process
• Hydrocarbons with the smallest molecules have the lowest boiling points
• They are piped out the top of the column as gases
• The fractions have high boiling points at the bottom; they cool to form liquids or solids at room temperature

Question 6

Alkanes

Answer 6

Alkanes are saturated hydrocarbons. All the carbon-carbon bonds are single covalent. This means that they contain as many hydrogen atoms as possible in each molecule. No more hydrogen atoms can be added.

Question 7

Alkane formula

Answer 7

CnH2n + 2

Question 8

Hydrocarbon properties

Answer 8

• flammable
• ignite easily and burn well

Question 9

complete combustion

Answer 9

When hydrocarbons burn in air they transfer lots of energy to the surroundings.
The carbon and hydrogen in the fuel are oxidised completely when they burn like this.

Question 10

Incomplete combustion

Answer 10

When there is not enough oxygen to burn.
Carbon monoxide is produced as a product which is a toxic gas.

Question 11

Cracking

Answer 11

Cracking is a thermal decomposition reaction.
Large hydrocarbon molecules can be broken into smaller molecules by passing the vapours over a hot catalyst or by mixing them with steam and heating them to a high temperature.

Question 12

Alkene test

Answer 12

Alkenes compounds containing carbon-carbon double bonds react with orange bromine water, turning it colourless.

Question 13

Alkene formula

Answer 13

CnH2n