C6.2

Question 1

Hydrocarbons

Answer 1

Compounds that only contain hydrogen and carbon atoms

Question 2

What are alkanes

Answer 2

Homologous hydrocarbons

Question 3

Why do alkanes from a homologous series

Answer 3

They have common features :
-same general formula
-carbon atoms are joined together by single covalent bonds
All alkanes are SATURATED

Question 4

Are alkanes saturated or non saturated

Answer 4

Saturated

Question 5

General formula for alkanes

Answer 5

CnH2n+2
Each successive member differs by a CH2 group

Question 6

How do alkanes react

Answer 6

Through combustion
If there is a plentiful supply of oxygen or air , complete combustion happens

Question 7

Are the atoms oxidised or reduced during combustion

Answer 7

Carbon atoms are oxidised , forming carbon dioxide
Hydrogen atoms are oxidised , forming water

Question 8

What happens if there is a poor supple of oxygen or air during combustion

Answer 8

Incomplete combustion happens instead
Water is formed , but carbon is only oxidised to carbon monoxide , CO
Some carbon atoms may not be oxidised if there is a further lack in oxygen or air , forming C

Question 9

Why is CO bad

Answer 9

It is a toxic gas and can cause suffocation

Question 10

Crude oil

Answer 10

A fossil fuel formed from the remains of marine organisms that died millions of years ago , turning into crude oil due to chemical reactions

Question 11

Finite resources

Answer 11

No longer being made or are being made extremely slowly , and is being used up faster than being formed

Question 12

Features of a homologous series

Answer 12

Saturated - all atoms joined together by simple covalent bonds
Same general formula
All differ by CH2

Question 13

What type of compounds are alkanes

Answer 13

Colourless , but have gradual physical property changes as the number of carbon atoms in the chain increase
Generally unreactive

Question 14

CH4

Answer 14

Methane

Question 15

C2H6

Answer 15

Ethane

Question 16

C3H8

Answer 16

Propane

Question 17

C4H10

Answer 17

Butane

Question 18

Name the first four alkanes

Answer 18

Methane , ethane , propane , butane

Question 19

What are alkenes

Answer 19

Hydrocarbons that form a homologous series

Question 20

What is the main difference between alkanes and alkenes

Answer 20

Alkene molecules contain a C=C double bond
This means that alkenes are unsaturated

Question 21

General formula for alkenes

Answer 21

CnH2n

Question 22

Functional group

Answer 22

An atom , or group of atoms , or type of bond in a molecule that uses responsible for the characteristic reactions of the substance

Question 23

In alkenes , which bond allows the substance to undergo additional reactions

Answer 23

The C=C double bond

Question 24

Addition reaction

Answer 24

An atom or group of atoms combines with a molecule to form a larger molecule , with no other
products formed

Question 25

Basic test for unsaturation

Answer 25

Bromine reacts with alkenes but not alkanes . Bromine water is orange brown , but will turn colourless if an alkene is mixed with it . It remains orange brown if an alkane is added to it

Question 26

Alkenes can also undergo addition reactions with hydrogen in the presence of

Answer 26

A nickel catalyst

Question 27

The more carbon atoms there are in the alkane molecules

Answer 27

-the larger the molecules -the stronger the intermolecular forces -the higher the boiling point

Question 28

How is crude oil made useful

Answer 28

It is made up of a mixture of hydrocarbons , mostly alkanes They are separated using fractional distillation . This works well because each alkane has a different boiling point

Question 29

Describe the process of fractional distillation - crude oil

Answer 29

-Crude oil is heated and it’s vapours are piped into the bottom of a fractionating column , which has a a temperature gradient ( hot at the bottom , cold at the top ) -Vapours cool as they rise through the column -each fraction contains many substances with similar boiling points

Question 30

Fraction

Answer 30

Separated parts of the crude oil

Question 31

Which alkane has the highest boiling point

Answer 31

Bitumen , during fractional distillation it leaves at the bottom of the column and is in the solid state at room temperature

Question 32

Which substances have the lowest boiling points during fractional distillation

Answer 32

Refinery gases - methane , ethane , propane , and butane have the lowest boiling points They reach the top and leave the column without cooling enough to condense

Question 33

The other substances

Answer 33

Are in liquid state at room temperature, they fall into trays and leave from the middle of the column