Unit 3: Section 3 - Alkenes and Alcohols

Question 1

Why type of hydrocarbon is an alkene?

Answer 1

An unsaturated hydrocarbon.

Question 2

What does unsaturated mean?

Answer 2

It means they are able to form more bond under the correct conditions.

Question 3

Why do carbon-carbon double bonds have a high electron density?

Answer 3

Because there are two pairs of electrons present.

Question 4

What are electrophiles?

Answer 4

Electron-pair acceptors

Question 5

What are polymers formed from?

Answer 5

Monomers

Question 6

How are addition polymers made?

Answer 6

When monomers join together to make long chains.

Question 7

What are polyalkenes?

Answer 7

Addition polymers made from alkenes.

Question 8

Why are addition polymers unreactive?

Answer 8

They are saturated and the main carbon chain is non-polar.

Question 9

What forces hold polyalkene chains together?

Answer 9

Van der Waals forces

Question 10

____, ________ polyalkene chains tend to be ______ and ______.
_____, _________ polyalkene chains tend to be _______ and ______________.

Answer 10

Long
Straight
Strong
Rigid
Short
Branched
Weaker
More flexible

Question 11

What does a plasticiser do and how does it work?

Answer 11

They make polymers more flexible by pushing polymer chains apart and reducing the strength of the intermolecular forced between the chains.

Question 12

What is PVC used to make? (2)

Answer 12

• Drainpipes

* Window frames

Question 13

What is plasticised PVC used to make?

Answer 13

• Electrical cable insulation
• Flooring tiles
• Clothing

Question 14

How do you determine whether an alcohol is primary, secondary or tertiary?

Answer 14

By looking at which carbon the hydroxyl group is bonded to.

Question 15

What is a biofuel?

Answer 15

A fuel that’s made from biological material that’s recently died.

Question 16

What are the advantages of using biofuels? (2)

Answer 16

1. Biofuels are renewable energy sources. Unlike fossil fuels, biofuels won’t run out, so they’re more sustainable.
2. Biofuels are classed as carbon neutral so they produce carbon dioxide which is then absorbed by plants.

Question 17

What does carbon neutral mean?

Answer 17

Carbon neutral means that they do not contribute to or remove the carbon dioxide in the atmosphere.

Question 18

What are the disadvantages of using biofuels? (2)

Answer 18

1. Petrol car engines have to be modified to use fuels with a high ethanol concentration.
2. When land is used to grow crops for fuel that land isn’t being used to grow food.

Question 19

How do you oxidise alcohol? (2)

Answer 19

1. By burning them.

2. By using an oxidising agent such as acidified potassium dichromate (VI)

Question 20

What do determines what an alcohol oxidises to?

Answer 20

The structure of the alcohol

Question 21

Which type of alcohol oxidises to what?

Answer 21

• Primary alcohols oxidise to aldehydes and then carboxylic acids.
• Secondary alcohols oxidise to ketones.
• Tertiary alcohols do not oxidise.

Question 22

Why do tertiary alcohols not oxidise easily?

Answer 22

They don’t react with potassium dichromate. You can only oxidise them by burning them.

Question 23

How do you oxidise a secondary alcohol?

Answer 23

Using potassium dichromate under reflux.

Question 24

How can you distinguish between aldehydes and ketones?

Answer 24

• Fehling’s solution

* Tollens’ reagent

Question 25

How do you produce a carboxylic acid?

Answer 25

Oxidise a primary alcohol under reflux using potassium dichromate.

Question 26

How do you produce an aldehyde?

Answer 26

Distill a primary alcohol after it has been oxidised by potassium dichromate.

Question 27

How does Fehling’s solution distinguish aldehydes and ketones?

Answer 27

Fehling’s solution is a deep blue solution which stays blue with a ketone and changes to brick red when an aldehyde is present.

Question 28

How does Tollens’ reagent distinguish aldehydes and ketones?

Answer 28

Tollens’ reagent turns silver in the presence of an aldehyde but not in the presence of a ketone.