4.7- Organic Chemistry

Question 1

What is crude oil?

Answer 1

Crude oil is a type of fossil fuel. It is a finite resource found in the Earth’s crust. It is formed over millions of years from the remains of ancient biomass.

Question 2

How is crude oil formed?

Answer 2

1. Millions of years ago, there were many tiny animals and plants in the sea.
2. When they died, they fell to the bottom of the sea.
3. At the bottom of the sea, they were covered in mud.
4. Over time, layers of rock built up on top.
5. The rock put the dead organisms in hot, high pressure and low oxygen conditions.
6. These conditions, over millions of years, formed crude oil.

Question 3

What are hydrocarbons?

Answer 3

molecules made up of hydrogen and carbon atoms only

Question 4

What are alkanes?

Answer 4

Alkanes are saturated hydrocarbons (one-bond)- there are as many hydrogen atoms as possible in each molecule

Question 5

What type of series are alkanes?

Answer 5

Alkanes are a type of homologous series.
They are a group of chemical compounds with similar chemical properties and the same functional group
A functional group gives a compound specific properties.

Question 6

What is the general formula of alkanes?

Answer 6

The general formula of alkanes is: CnH2n+2, where n is the number of carbon atoms in the compound.

Question 7

How is carbon bonded to hydrogen in alkanes?

Answer 7

Each carbon atom is covalently bonded to 4 hydrogen atoms.

Question 8

What are the first four alkanes?

Answer 8

Methane- CH4
Ethane- C2H6
Propane- C3H8
Butane- C4H10

Question 9

How does fractional distillation of crude oil work?

Answer 9

1. The oil is heated until most of it has turned into gas. The gases enter a fractionating column.
2. In the column, there is a temperature gradient (its hot at the bottom and gets cooler as you go up).
3. The longer hydrocarbons have high boiling points and condense back into liquids and drain out of the column earlier on, when they’re near the bottom. The shorter hydrocarbons have lower boiling points so they condense and drain out much later on, near to the top of the column, where it is cooler.
4. You end up with the crude oil mixture separated out into different fractions. Each fraction contains a mixture of hydrocarbons that all contain a similar number of carbon atoms, so they all have similar boiling points.

Question 10

What is a fraction?

Answer 10

Fractions- molecules of similar chain length and boiling point which are collected at the same point.

Question 11

Which type of hydrocarbons are the most useful?

Answer 11

short chain molecules are the molecules that are most useful, since they ignite easily and burn well, with less smokier flames than long chain hydrocarbons.

Question 12

What is the difference between long and short chain hydrocarbons in terms of boiling point?

Answer 12

Short chain hydrocarbons have a lower boiling point

Long chain hydrocarbons have a higher boiling point

Question 13

What is the difference between long and short chain hydrocarbons in terms of volatility (the tendency to turn into a gas)?

Answer 13

Short chain hydrocarbons have a higher volatility

Long chain hydrocarbons have a lower volatility

Question 14

What is the difference between long and short chain hydrocarbons in terms of viscosity (how easily it flows)?

Answer 14

Short chain hydrocarbons are very runny

Long chain hydrocarbons are very thick

Question 15

What is the difference between long and short chain hydrocarbons in terms of flammability?

Answer 15

Short chain hydrocarbons have a higher flammability

Long chain hydrocarbons have a lower flammability and burn with a smokier flame

Question 16

What is required for combustion to take place?

Answer 16

Heat, fuel and oxygen are required for combustion to take place.
Combustion is where fuel reacts with oxygen to release useful energy.

Question 17

How do alkanes combust?

Answer 17

With an adequate supply of air (oxygen) they react to form carbon dioxide and water
This is called complete combustion
EG. methane + oxygen → carbon dioxide + water

Question 18

What is combustion an example of?

Answer 18

Combustion is an example of an oxidation reaction, as both the carbon and hydrogen gain oxygen.

Question 19

What is incomplete combustion?

Answer 19

This is when alkanes react with a limited supply of oxygen to form carbon monoxide and water.

Methane + oxygen → carbon monoxide + water
2 CH4 + 3 O2 → 2CO + 4H2O

Question 20

Why is carbon monoxide poisonous?

Answer 20

Carbon monoxide is highly poisonous- it binds to haemoglobin instead of oxygen.

Question 21

What is cracking?

Answer 21

Breaking long chain hydrocarbons into short chain ones

Question 22

What is cracking an example of?

Answer 22

thermal decomposition reaction

Question 23

How does catalytic cracking work?

Answer 23

Long alkane → short alkanes and alkene
Vaporise hydrocarbons and heat it too 500 degrees celsius, mixing with a catalyst

Question 24

How does steam cracking work?

Answer 24

Vaporise hydrocarbons and mix it with steam, then heating it to a very high temperature.

Question 25

What are alkenes and alkanes used for?

Answer 25

Alkanes are used as fuels, alkenes are used to produce polymers and as starting materials for the production of many other chemicals.

Question 26

What is an alkene?

Answer 26

An alkene is a type of hydrocarbon that contains a carbon- carbon double bond.

Question 27

How do you test for alkenes?

Answer 27

We test for alkenes with bromine water, as alkenes are more reactive than alkanes and therefore they can react with orange bromine water, turning it colourless.

Question 28

What is a functional group?

Answer 28

Functional group- an atom or group of atoms that give organic compounds their characteristic reactions.

Question 29

What is a homologous series?

Answer 29

Homologous series- a group of related organic compounds that have the same functional group but differ by the sequential addition of a CH2 group.

Question 30

What is the general formula for alkenes?

Answer 30

CnH2n

Question 31

Where do you draw the double bond in alkenes and what does the double bond mean?

Answer 31

Always draw the double bonds between the first and second carbon atoms in the carbon chain. The presence of the C = C makes the molecules unsaturated.

Question 32

How do alkenes burn?

Answer 32

Alkenes burn with a smokier yellow flame. They also release less energy per mole in combustion than alkanes. This is why alkanes are used as fuels, and alkenes are not.

Question 33

How do addition reactions work?

Answer 33

Addition reactions- Molecules are ‘added’ across the double bond.

Question 34

How do alkenes react with halogens?

Answer 34

The reaction takes place at room temperature and forms haloalkanes.

Question 35

How do alkenes react with hydrogen?

Answer 35

Takes place at 150℃ and with a Nickel catalyst. Forms an alkane

Question 36

How do alkenes react with water?

Answer 36

Takes place under high pressure and temperature with a catalyst. Is a reversible reaction Forms an alcohol

Question 37

What is a polymer?

Answer 37

Polymers- a substance made from very large molecules made up of many repeating units.

Question 38

What is a monomer?

Answer 38

Monomer- small reactive substances that react together in repeating sequences to form a large molecule.

Question 39

What are the two types of polymer?

Answer 39

Two types of polymer: Synthetic (eg. plastic) Natural (eg. proteins)

Question 40

How are polymers made?

Answer 40

Polymers are made in a polymerisation reaction. When alkenes are used, this is an addition reaction, which happens many times over to join lots of molecules into one long chain.

Question 41

How do you draw an addition polymer?

Answer 41

Break open the double bond Add square brackets- make sure the bonds go through the brackets. Add a small ‘n; at the bottom right corner, to show that this is repeated ‘n’ times over.

Question 42

How do you name polymers?

Answer 42

Put monomer name in brackets. Add ‘poly’ in front of the brackets. Eg. ethene →poly(ethene

Question 43

What is polymerisation?

Answer 43

Polymerisation- the process where many monomers bond together in long chains to form a monomer.

Question 44

Why is it called addition polymerisation?

Answer 44

This is addition polymerisation because no other substance is formed, only the monomer repeats.