1Wallace Hall Academy

2020/2021

Wallace Hall Academy

S3

CHEMISTRY

TOPIC 1

Crazy CarbonUpdate 2020/2021

NameClass

Pupil Notes

TEACHER ANSWER BOOKLET

In this topic the learning objectives you will cover are:

Learning Objective R A G State that a chemical reaction is a change in which a new substance is

formed. Identify the changes in appearance and energy which show a chemical

reaction has taken place. Be able to write word equations to represent reactions. State that a fuel is any substance that burns to release energy. Describe how crude oil is formed and turned into useful products. State that the alkanes are a subset of hydrocarbons. Name the first 8 molecules of the alkane family. Draw full structural formulae, write chemical formulae and write

shortened structural formulae for the first 8 molecules of the alkane family.

Write the general formula of the alkanes. State that the alkenes are a subset of hydrocarbons. Name the first 8 molecules of the alkene family. Draw full structural formulae, write chemical formulae and write

shortened structural formulae for the first 8 molecules of the alkene family.

Write the general formula of the alkenes. State that the cycloalkanes are a subset of hydrocarbons. Name the first 8 molecules of the cycloalkane family. Draw full structural formulae, write chemical formulae and write

shortened structural formulae for the first 8 molecules of the cycloalkane family.

Write the general formula of the cycloalkanes. State that alkenes are unsaturated molecules. State that alkanes and cycloalkanes are saturated molecules. State that bromine is used to test for unsaturation and the colour

change is from orange to colourless. State that an unsaturated molecule is one which contains a carbon to

carbon double bond. State that a saturated molecule is one which does not contain a carbon

to carbon double bond. State that the reaction of an alkene with bromine is an addition

reaction. State that the reaction of an alkene with hydrogen (hydrogenation) is

an addition reaction. State that when an alkene reacts with hydrogen an alkane is formed. Be able to name the products of addition reactions.

Learning Objective R A G State that a homologous series is a family of molecules with the same

general formula and similar chemical properties. Write the systematic names of straight chain and branched alkanes

2Wallace Hall Academy

2020/2021

and alkenes. State that as the size of a hydrocarbon increases, the viscosity

increases. State that as the size of a hydrocarbon increases the flammability

decreases. State that as the size of a hydrocarbon increases the rate of

evaporation decreases. State that as the size of a hydrocarbon increases the boiling point

increases. Explain why boiling point increases as chain length increases. Explain why branched chain molecules have lower boiling points than

straight chain isomers. State that Fractional Distillation is the process by which crude oil is

separated into fractions. State that a fraction is a group of hydrocarbons with a boiling point

range. State the uses of the fractions produced through fractional distillation. State that cracking is a process used to break up long chain

hydrocarbons into short chain hydrocarbons. State that cracking is carried out because there is a greater demand for

short chain hydrocarbons than long chain hydrocarbons.* Know that alkenes can be used to make plastics. Use the name of a monomer to work out the name of the polymer. Draw a short section of a polymer when given a monomer. Draw the repeating unit for a polymer. State at least one use for alkanes, alkenes and cycloalkanes. To be able to calculate the GFM of any substance. To be able to calculate the number of moles of a substance using the

formula in the data booklet.

Chemical Reactions

If we observe the world around us, we can see that most things change over time. Not all of these changes are chemical reactions;

3Wallace Hall Academy

2020/2021

Learning Objectives: State that a chemical reaction is a change in which a new substance is formed. Identify the changes in appearance and energy which show a chemical

reaction has taken place. Write word equations to represent reactions.

some are simply changes of state. For a change to be classed as a chemical reaction, a new substance must be formed. Chemical reactions tend to be irreversible because the new substance often can’t be turned back into what they started as.

In S2 you found out that there are several observations we can make that tell us if a change is a chemical reaction or not. The following changes would show a chemical reaction has probably taken place:

Changes in appearance Changes in energy Colour change Heat produced Solid formed Light produced Gas formed Sound produced

Electricity produced

Your teacher will demonstrate some of the following experiments. You will have to make observations in order to determine if any of the experiments are chemical reactions.

Observation Elephants’ Toothpaste

Copper sulfate and

water

Copper turnings & nitric acid

Colour change

Solid formed

4Wallace Hall Academy

2020/2021

Gas formed

Heat produced

Light produced

Sound produced

Reversible

Chemical Reaction

When copper reacts with nitric acid, copper nitrate and hydrogen gas are formed. Write a word equation to show this:

5Wallace Hall Academy

2020/2021

Copper + nitric acid copper nitrate + hydrogen gas

You could look these experiments up online, elephants toothpaste is my favourite!

Writing Word Equations

When writing word equations, we leave out states (solid, liquid and gas), colours and heat.Use the sentences below to create word equations. The first one has been done for you.

1. When magnesium ribbon burns, it reacts with oxygen in the air to form magnesium oxide, a white powder.

magnesium + oxygen magnesium oxide

2. In the Blast Furnace, iron is made by reacting iron trioxide with carbon monoxide gas. Carbon dioxide gas is also produced.

Iron trioxide + carbon monoxide iron + carbon dioxide

3. In the Haber Process, nitrogen, which we get from the air, reacts with hydrogen gas in the presence of a platinum catalyst to form ammonia (nitrogen hydride) which can be used to make many things including fertilisers.

Nitrogen + hydrogen ammonia (or nitrogen hydride)

4. When calcium metal is added to water, a gas is given off and calcium oxide solution is formed. When tested with a burning splint, the hydrogen gas "popped". Calcium + water calcium oxide + hydrogen

5. Aluminium is a reactive metal but protected by a layer of corroded metal. Chlorine gas can penetrative the corrosion to produce aluminium chloride. Aluminium + Chlorine aluminium choride

Fuels

6Wallace Hall Academy

2020/2021

Learning Outcomes: State that a fuel is a substance that burns to release energy To revise advantages and disadvantages of different fuels To describe how crude oil is formed To revise combustion reactions

Word equations are used by chemists to summarise what is happening in a reaction. You could use a word equation to instruct someone how to make your favourite sandwich a.s.a.p.! Make your own version below:

Granary bread + ham + cheese+ chili jam Yummy sandwich Reactants Products

platinum

We rely on fuels to produce the energy that we need to power our lives! Fuels can be a controversial issue and scientists are investing a lot of time in researching new technology to improve the sustainability of our fuel use.

In S2, we explored a number of different fuels that are being developed as alternatives to fossil fuels. Complete the summary box below to show what you already know.

Fuel How is it made/where does it come from?

Advantages Disadvantages

We also learnt in S2 that burning a fuel is an exothermic reaction – that means it gives out a lot of heat. We rely on this heat so much that since the 1970's, approximately 39 billion barrels of oil have been extracted in Scotland and current estimates suggest that there are up to 24 billion still to be extracted.

7Wallace Hall Academy

2020/2021

RESEARCH TASK:

Some of the fuels you could look up include biofuel, ethanol, hydrogen, and vegetable oil, wood. You could also include fossil fuels such as oil (petrol/diesel), coal or natural

gas.

Many of the skills developed in this sector will continue to play a vital role in developing our future, both within oil and gas but also through their transfer and adaptability to other sectors such as offshore wind and Carbon, Capture and Storage.

In our bid to find more oil we are now starting to drill in the once pristine Arctic and there is a threat that we will soon be exploring for oil in the so far untouched Antarctic.  But why are we driven to endanger these environments? Why is oil so important to our modern lifestyles? What is it made of and how is it processed?

Formation of Fossil FuelsYour teacher will show you an animation or let you try the edible crude oil activity. AnimationNumber the statements 1-5 below to describe how crude oil is formed:

Oil is less dense than water so rose up through permeable rocks

5

Layers of sediment built up and started to change into rock 3Millions of years ago, huge numbers of microscopic plants and animals died and sank to the bottom of the sea

1

The temperature and pressure below the rock ‘cooked’ the remains, turning them into crude oil

4

Their remains were covered by mud 2Questions:

1. What is a fuel?A substance that can be burned to release energy/substance that reacts with oxygen to produce useful energy (or something similar)

2. Why is crude oil known as a fossil fuel?Crude oil was formed in a similar way to fossils/it is formed by the fossilisation and preservation of dead animals and plants

8Wallace Hall Academy

2020/2021

3. Crude oil is made of a mixture of compounds known as hydrocarbons. Which two elements do you think these contain?

Hydrogen & Carbon

4. What the other two fossil fuels, besides oil?Coal and natural gas

5. One of the fuels that we get from crude oil is camping gas. The chemical name for this compound is propane.

We found in S2 that the products of burning a fuel, like propane, are carbon dioxide and water.

Write a word equation to show the complete combustion of propane:

+

9Wallace Hall Academy

2020/2021

Propane oxygen Carbon dioxide Water

Challenge Task: Make a cartoon strip to show the formation of crude oil.

+ +

Hydrocarbons

In order to understand why crude oil is so useful and how we make it useful, we need to know what it is made of:

Just like Ben & Jerry’s, crude oil is made up of a mixture of substances. Some of the substances in crude oil are shown below:

We are just going to focus on three of the important hydrocarbon families from crude oil: the alkanes, the cycloalkanes and the alkenes.

Alkanes

Alkanes are a group of hydrocarbons that are made up of chains of carbon atoms joined together by single covalent bonds (more

10Wallace Hall Academy

2020/2021

Learning Objectives: State that the alkanes are a subset of hydrocarbons. Name the first 8 molecules of the alkane family. Draw full structural formula, write chemical formula and write shortened

structural formula for the first 8 molecules of the alkane family. Write the general formula of the alkanes.

about these bonds in another topic!). Each carbon atom has the maximum number of hydrogen atoms that can bond to it and they are often described as being saturated.

One of the main molecules in petrol is an alkane :

You are now going to build a model of the first molecule in the alkane family using moly mods. But first you need to work out how many bonds a carbon atom will form and how many bonds a hydrogen atom will form.

Carbon atoms form 4 bonds and hydrogen atoms form 1 bond .

The first molecule in the alkane family has just one carbon atom. Using what you have written about the number of bonds above, make a model of this molecule using the moly mods. Now make a sketch of this molecule in the box below.

Sketch of an alkane

11Wallace Hall Academy

2020/2021

This is just a sketch so anything that shows one carbon atom attached to 4 hydrogen is

acceptable!

Naming Hydrocarbons

The name of any hydrocarbon molecule is determined by the number of carbon atoms it is made of and the subset family it belongs to.

The first part of the name of any hydrocarbon is a prefix denoting the number of carbon atoms in the molecules. The prefixes for 1 to 8 carbon atoms are shown in the table below with a mnemonic to help you remember them.

The second part of the name of any hydrocarbon comes from the name of the family it belongs to i.e. the name of every alkane molecule ends in ‘ane’. So our alkane family contains methane, ethane, propane, butane etc.

In addition to naming hydrocarbons we need to be able to draw their full structural formula and write their chemical formula. You also need to be able to write shortened structural formula, created by taking each carbon atom individually and then writing everything that is attached to it. When writing chemical and shortened structural formulae, we use subscript numbers to show how many of each atom we have.

12Wallace Hall Academy

2020/2021

Mnemonic Prefix Number of carbon atoms

Monsters Meth 1Eat Eth 2People Prop 3But But 4

Prefer Pent 5

Hairy Hex 6

Haggis Hept 7

Omelettes Oct 8

CH3CH2CH3

Now fill in all of the information about the first 6 alkanes in the table on the next page, the first two have been done for you.

General formula

Each family of hydrocarbons has its own general formula in which n denotes the number of carbon atoms. This way it acts as a simple expression allowing you to calculate the number of hydrogen atoms present in any molecule from that family as long as you know the number of carbon atoms. The general formula for the alkanes is CnH2n+2. Use the general formula to check you would get the correct chemical formula for an alkane with 4 carbon atoms, then an alkane with 15 carbon atoms.

C4H10 C15H32

13Wallace Hall Academy

2020/2021

Full structural formula Shortened structural formula

Name Full structural formulaChemical Formula

Shortened structural formula

methane CH4 CH4

ethaneH Hl l

H - C – C – Hl lH H

C2H6 CH3CH3

propane

C3H8 CH3CH2CH3

butane C4H10 CH3CH2CH2CH3

pentane C5H12 CH3CH2CH2CH2CH3

hexane

14Wallace Hall Academy

2020/2021

Alkanes

General formula CnH2n+2

Learning Objectives:* State that fractional distillation is the process used to separate the hydrocarbons in crude oil Know how the length of the hydrocarbon chain affects the properties of the

molecule Explain why the boiling point increases as chain length increases Explain why branched chain molecules have lower boiling points than straight

chain isomers

Challenge Task: (a) Complete the formula for the following alkanes:

C16 H 34 C36 H 74 C 25 H52 C22 H46(b) Write the shortened structural formula for the first alkane shown above

PropertiesCrude oil is one of the most important fossil fuels we have because it is a mixture of a huge number of different hydrocarbons which are all extremely useful. The crude oil mixture has to be separated in a special process so that we can collect the different hydrocarbons separately and make use of them. Your teacher will show you an animation to show you how fractional distillation works. video clip

It is only possible to separate the hydrocarbons in the crude oil mixture because they have different properties. We will now investigate how these properties are related to the size of the hydrocarbon molecule.

Experiment 2: How the properties of a hydrocarbon are related to it’s size Viscosity experiment Flamability experiment

Size of molecules Viscosity Boiling Point Rate of

Evaporation FlammabilitySmall

(hexane)Medium

15Wallace Hall Academy

2020/2021

Name of Fraction Use

Size of molecul

esmall

very large

(paraffin)Large

(squalene)

Conclusion: As the size of a hydrocarbon increases the viscosity

As the size of a hydrocarbon increases the flammability As the size of a hydrocarbon increases the rate of evaporation As the size of a hydrocarbon increases the boiling point

16Wallace Hall Academy

2020/2021

Challenge Task: Use your data booklet to find the boiling points of the first 8 alkanes. Plot a line graph of boiling point against the number of carbon atoms in the alkane.

Boiling Point and Structure

The way that a substance behaves can always be explained by its chemical structure. Consider the small and large chain molecules from the previous experiment. Suggest why the longer chain molecule has a higher boiling point:

The alkanes that we have studied so far are known as ‘straight chain’ alkanes because the carbon atoms are linked consecutively in the main chain. Branched chain hydrocarbons also exist. These are often added to petrol to make it burn more smoothly.

Butane (C4H10) 2-methylpropane (C4H10)

To check if your prediction is correct, complete the following table using p9 of your data booklet:

Alkane Boiling Point 0COctaneEthaneButane2-methylpropane

17Wallace Hall Academy

2020/2021

I think that octane would have a higher boiling point than ethane because

I think that …………………………………. will have a higher boiling point than …………………………………… because:

As the chain length of an alcohol increases, the boiling point

increases. This is because there are a greater number of

attractions between the molecules, so more energy is needed to overcome

these. Branched chain molecules have lower boiling points than

straight chain molecules with the same chemical formula. This is because

the branched structure makes it more difficult for molecules to pack

together, therefore less energy is needed for boiling.

Questions:

1.Use your data booklet to predict the boiling point of Nonane

2.Write the chemical formula for (a) hexane and (b) 2-methylpentane

3. Explain why these substances have different boiling points.

4.What conclusion can be drawn about the relationship between the number of carbon atoms in a straight chain alkane and the boiling point of the molecule?

Systematic Names

We can see that a number of differently structured molecules can all have the same chemical formula. These are known as isomers.

If we were to call each of the three isomers of pentane by the same name (pentane), we would not know which of the three structures the molecule in question actually had. It is for this reason that we name molecules systematically.

Naming straight chain alkanes

18Wallace Hall Academy

2020/2021

Learning Objectives: Write the systematic names of straight chain and branched hydrocarbons.

1. Main chain → hexane2. Branches → ethyl and methyl3. Position → 3,44. Name: 3-ethyl-4-

methylhexane

1. Main chain → hexane2. Branches → methyl x 2 =

dimethyl3. Position → 3,44. Name: 3,4-dimethylhexane

Straight chain alkanes are simply given the names you wrote on page 14.

Naming branched alkanes

1. First identify the main chain in the molecule (this is the longest chain).

2. Name the branches and if there is more than one type alphabetise. (The names of all branches end in ‘yl’ and start with the prefix which denotes the number of carbon atoms it contains e.g. the name of the branch opposite would be methyl.)

3. Number the carbon atoms in the main chain making sure that the carbon attached to the branch whose name is first alphabetically has the smallest possible number.

4. Finally use commas between numbers and dashes between numbers and letters.

* Look at how the examples on the next page were named before trying some for yourself.

Name of alkane Structure

19Wallace Hall Academy

2020/2021

CH3 l

H3C - CH - CH – CH2 - CH2 - CH3 l CH3

Name of alkane Structure

2,2-dimethylpropane

2,2,5-trimethylhexane

20Wallace Hall Academy

2020/2021

4-ethyloctane

21Wallace Hall Academy

2020/2021

Alkenes

A second family of hydrocarbon molecules are the alkenes. These are formed from alkanes using a process called cracking. Alkenes are used to make plastics; we will investigate this later in the course.

Be careful not to get alkenes confused with alkanes: alkenes have double e in the name and a double bond in their structure!

The chemical formula for the first molecule in the alkene family is C2H4. Try to work out the structure of this molecule using moly mods. Now make a sketch of this molecule in the box below. Try to make the second molecule in the family and draw a sketch. Now try and name the two molecules you have made.

1st alkene 2nd alkene

Now fill in all of the information about the first 7 alkenes in the following table. See if you can work out the alkenes general formula.

22Wallace Hall Academy

2020/2021

Learning Objectives: State that the alkenes are a subset of hydrocarbons. Name the first 8 molecules of the alkene family. Draw full structural formula, write chemical formula and write shortened

structural formula for the first 8 molecules of the alkene family. Write the general formula of the alkenes. Know that alkenes are produced a process known as cracking

Name Full structural formulaChemical Formula

Shortened structural formula

23Wallace Hall Academy

2020/2021

General formula

Naming straight chain alkenes

Number the carbon atoms in the chain making sure that one of the carbon atoms attached to the double bond is given the smallest number possible. This allows you to show the position of the double bond in the name e.g. the name of the alkene below would be pent-2-ene.

Naming branched alkenes

1. First identify the main chain in the molecule (this is the longest chain which contains the carbon to carbon double bond).

2. Number the carbon atoms in the main chain making sure that one of the carbon atoms attached to the double bond is given the smallest number possible.

3. Name the branches in the same way you did for the alkanes.

4. Finally use commas between numbers and dashes between numbers and letters.

* Look at how the examples on the next page were named before trying some for yourself.

24Wallace Hall Academy

2020/2021

1. Main chain → hex-1-ene2. Branches → methyl x 2 =

dimethyl3. Position → 34. Name: 3,3-dimethylhex-1-ene

1. Main chain → hex-2-ene2. Branches → ethyl 3. Position → 34. Name: 3-ethylhex-2-ene

Name of alkene Structure

Name of alkene Structure

25Wallace Hall Academy

2020/2021

3,4-dimethylhept-2-ene

2-methylpropene

2,2,5-trimethylhex-3-ene

You choose:

26Wallace Hall Academy

2020/2021

Learning Objectives: State that the cycloalkanes are a subset of hydrocarbons. Name the first 8 molecules of the cycloalkane family. Draw full structural formulae, write chemical formulae and write shortened

structural formulae for the first 8 molecules of the cycloalkane family. Write the general formula of the cycloalkanes.

Cycloalkanes

The third family of hydrocarbon molecules is called the cycloalkanes. They are often used as fuels and solvents. The chemical formula for the first molecule in the cycloalkane family is C3H6. Try to work out the structure of this molecule using moly mods, remember these molecules are different to the alkenes. Now make a sketch of this molecule in the box below. Try to make the second molecule in the family and draw a sketch. Now try to name the two molecules you have made.

1st cycloalkane 2nd cycloalkane

Now fill in all of the information about the first 6 cycloalkanes in the table on the next page. See if you can work out the cycloalkanes’ general formula.

Name Full structural formulaChemical Formula

Shortened structural formula

27Wallace Hall Academy

2020/2021

General formula __________________

Reactions of Alkenes

The double bond in alkenes is pretty reactive. This bond can ‘open up’ and ‘grab’ other molecules! Make a model of the above reaction and see for yourself!

28Wallace Hall Academy

2020/2021

ethene hydrogen ethane

Learning Objectives: State that alkenes are unsaturated molecules. State that alkanes and cycloalkanes are saturated molecules. Know that alkenes take part in addition reactions. State that bromine is used to test for unsaturation and the colour change is

from orange to colourless.

Try the same reaction but start with a molecule of propene. Write an equation like the one shown above to represent this reaction:

This reaction is known as an ‘addition’ reaction. This can be handy for making loads of useful products! For example, vegetable oils can be ‘hardened’ for use in spreads by hydrogenating some of the double bonds in the molecules.

For each of the reactions below make models and then write an equation using full structural formula, with a chemical equation below.

But-1-ene & hydrogen gas (H2)

____________ + ____________ → ____________

____________ + ____________ → ____________

But-2-ene & hydrogen bromide (HBr)

____________ + ____________ → ____________

____________ + ____________ → ____________

Propene & bromine (Br2)

____________ + ____________ → ____________

29Wallace Hall Academy

2020/2021

____________ + ____________ → ____________

Name the product in each of the above reactions:(i)

(ii)

(iii)

.

Testing for Unsaturation

Molecules that contain double bonds are known as ‘unsaturated’ molecules. We can use the fact that unsaturated molecules react with bromine as a chemical test for unsaturation. If a molecule is unsaturated, it will decolourise bromine water.

Aim:

Labelled diagram:

Results:

Name of hydrocarbon

Type of hydrocarbon

Observations with bromine

Saturated or Unsaturated?

Conclusion:Alkanes and cycloalkanes cannot react with ____________ because they are saturated molecules; that is, they do not contain a carbon to

30Wallace Hall Academy

2020/2021

carbon ____________ ____________. This means there are never any bonds free to join with other atoms such as bromine.

1. Complete an equation below to show what happened when the alkene in the above experiment reacted with the bromine water. Write the full structural formula then the molecular formula underneath:

____________ + ____________ → ____________

____________ + ____________ → ____________

2. What name is given to this type of reaction?

3. For each of the following molecules (i) predict if it would react with bromine and (ii) draw and name the product of the reaction:

ReactantReaction

with bromine?

Structure of product

Name of product

Cyclobutane

Pent-1-ene

Propane

Ethene

31Wallace Hall Academy

2020/2021

Learning Objectives: Plastics (polymers) can be made in a process called polymerisation. An addition polymer is a polymer which is formed by an addition reaction when

the carbon to carbon double bonds in the monomers break allowing the monomers to join together.

The reaction in which an addition polymer is formed is called addition polymerisation.

The structure of the polymer can be drawn from the structure of the monomer and vice versa.

The name of the polymer can be deduced from the name of the monomer.

Making Plastics

We use plastics and synthetic fibres everyday yet these have only been widely used in the past 50 years.

Plastics and synthetic fibres are man-made materials, this is why they are called SYNTHETIC.

Plastics are generally cheap to produce, and have very useful properties such as: lightness, strength and durability.

In addition, plastics are easily moulded into a variety of shapes and are excellent insulators of both heat and electricity.

Example of object made from plastic

Advantages of making from plastic

32Wallace Hall Academy

2020/2021

Currently, almost all plastics are produced from molecules, which have come from crude oil.

The molecules in crude oil are first separated by FRACTIONAL DISTILLATION.

CRACKING breaks down large hydrocarbon molecules into smaller molecules. This also produces ALKENES.

ETHENE is a very important molecule in the manufacture of plastics. In 2005 world production exceeded 75 million tonnes.

Plastics are very useful but can cause many issues. This is why scientists are now working to develop new kinds of plastics. How many disadvantages of using plastic can you give? You may watch a video first.

Disadvantage Issues caused Solutions

How are alkenes used to make plastics?

Plastics belong to a family of compounds known as polymers. A polymer is a long-chain molecule.

33Wallace Hall Academy

2020/2021

The term polymer is derived from the Greek poly, meaning many, and meros, meaning part. The name was given to polymer molecules because the long chain is made from many smaller molecules called monomers joined together. Monomers are the basic units of polymers.

Plastics and synthetic fibres are made from giant molecules.

Joining together many thousands of smaller molecules called MONOMERS makes these giant molecules.

The giant molecule is called a POLYMER as it is made by joining many small molecules together. POLY means many.

We are going to look at one type of polymer known as Addition Polymers. These can be formed by the adding together of alkenes. Can you guess which plastic is made by joining ethene molecules together?!

Addition Polymers & Addition Polymerisation

34Wallace Hall Academy

2020/2021

MonomerMonomer moleculesmolecules

Small part Small part of a of a polymerpolymer molecule.molecule.

join togetherjoin together

One of the bonds of the C=C breaks open, allowing the monomers to “ADD” to each, other, building up the polymer chain.

CHLOROETHENE

3 chloroethene molecules MONOMERS

Since the monomers join by addition reactions this is called ADDITION POLYMERISATION.

POLY(CHLOROETHENE)All addition polymers have a chain of C – C single bonds forming the backbone of the polymer molecule.

35Wallace Hall Academy

2020/2021

An addition polymer is a polymer which is formed by an addition reaction when the carbon to carbon double bonds in the monomers break allowing the monomers to join together.

The reaction in which an addition polymer is formed is called addition polymerisation.

You are now going to simulate addition polymerisation by attempting to make a small section of an addition polymer. Collect some molymods and make three molecules of ethene, these are the monomer in this particular polymer. Draw the full structural formula of the three molecules of ethene in the box below.

Three monomers of ethene:

The monomers are now going to join together to make a very small section of a polymer by undergoing addition polymerisation. To do this you need to break the carbon to carbon double bonds in the monomers. Draw the full structural formula of the small section of polymer you have just made in the box below. The name of the polymer is derived by simply placing poly in front of the name of the monomer.

A small section of the polymer: _________________________

Important: There is spare bond on each end of the section of polymer which must be included in drawings of polymers. Otherwise the diagram would depict a small molecule made of 6 carbon atoms rather than a small section of a polymer which, in reality, is made from thousands of monomers joined together.

36Wallace Hall Academy

2020/2021

+ +

_____________________ _____________________ _____________________

The repeating unit in a polymer can be identified from the structure of the polymer.

You will notice that the repeating unit is where the original monomers would have been. So identifying the repeating unit in a polymer allows us to determine the structure of the original monomers that made it. Draw one repeating unit for poly (ethene) in the box below and remember there is a spare bond on each end of the repeating unit which must be shown in the diagram.

One repeating unit of the polymer ______________:

Drawing polymers from more complex monomers

If we were asked to draw a section of the polymer formed from propene monomers, at first glance it might look slightly tricky. We can get round this by drawing the propene molecule as an H shape, where the middle of the H is the carbon to carbon double bond. To do this we simply condense the other branches around the double bond. Try the examples below for yourself.

37Wallace Hall Academy

2020/2021

→

Propene Propene in an H shape

→ Hex-1-ene Hex-1-ene in an H shape

→

Pent-2-ene Pent-2-ene in an H shape

38Wallace Hall Academy

2020/2021

Name of monome

r

Structure of

monomer

Section of polymer made from three

monomers

Name of polymer

One repeating unit of the polymer

Propene

Butene

poly(hexene)

Homologous Series

We have now looked at some of the chemical properties of three families of hydrocarbons as well as their different formulae.

39Wallace Hall Academy

2020/2021

Learning Objectives: State that a homologous series is a family of molecules with the same general

formula and similar chemical properties.

Addition Polymers & Addition Polymerisation

Complete the summary table below using what you have learned so far.

Family of Hydrocarbo

ns

Name of first

member

Full structural formula of

first member

General formula

Saturated or

Unsaturated

Uses

Alkanes

Alkenes

Cycloalkanes

* A homologous series is a family of molecules with the same general formula and similar chemical properties.

Each of the three families of hydrocarbons above is a homologous series,

as each molecule from the same family has the same ____________

formula and ____________ ____________ ________________ .

40Wallace Hall Academy

2020/2021

The Mole

No not this kind of mole! The chemistry mole!The mole is a unit of measurement used to express amounts of a chemical substance. The mass of one mole of a type of atom can be found on page ___ of the data booklet under relative atomic mass (RAM) and is measured in grams. The mass of one mole of the following would be:

Element Mass (g)Tin

LeadMercuryCarbonSodium

To work out the mass of one mole of a compound (substance made from more than one element bonded together), we need to do a bit more work. For example, to work out the mass of one mole of carbon dioxide we would do the following:

CO2

2 x 16 = 32 1 x 12 = 12

44So the mass of one mole of carbon dioxide = 44g. This is also known as the gram formula mass (GFM) of carbon dioxide.

Show full working to work out the mass of one mole of:

H2O NH3

41Wallace Hall Academy

2020/2021

Learning Objectives: Calculate the mass of one mole of any substance. Calculate the mass of different quantities of moles.

HNO3 H2 SO4

C6H12O6 hexene

42Wallace Hall Academy

2020/2021

Working out the mass of different numbers of moles

As you have just seen we can always work out the mass of one mole of any substance. Once you have got the mass of one mole, we can use it to work out the mass of different numbers of moles. For example, the mass of 5 moles of carbon dioxide would be calculated as follows:

5 moles of CO2 = mass of one mole x 5

5 moles of CO2 = 44 x 5 = 220 g

Try these examples yourself:

a) 0.3 moles of CO2 = mass of one mole x 0.3

0.3 moles of CO2 = _____ x 0.3 = ______g

b) 8 moles of H2O = mass of one mole x ____

8 moles of H2O = _____ x ___ = ______g

c) 0.1 moles of H2O = mass of one mole x ____

0.1 moles of H2O = _____ x ___ = ______g

d) 3.5 moles of SO2 = mass of one mole x ____

3.5 moles of SO2 = _____ x ___ = ______g

e) 0.35 moles of SO2 = mass of one mole x ____

0.35 moles of SO2 = _____ x ___ = ______

43Wallace Hall Academy

2020/2021

To calculate the mass of a substance we have simply multiplied the number of moles by the GFM. This leads to the expression: 

mass = number of moles x GFM Or m = n x GFM We can rearrange the formula to find the number of moles of a substance if we know its mass: 

number of moles = massGFM

 Or n = m

GFM

 

This can be simplified using a formula triangle.

Use your preferred method to calculate the following. Show ALL of your working.

a) How many moles are present in 5.4g of water?

44Wallace Hall Academy

2020/2021

Learning Objectives: Calculate the number of moles of a substance given its mass.

mm

This appears on p3 of your data book

m

GFMn

b) How many moles are present in 0.4g of ammonia (NH3)?

c) How many moles are present in 288g of calcium chloride (CaCl2)?

Key definitions – you must learn these definitions. You may want to make flash cards.Fuel A substance that can be burned to release energy

Alkane Saturated hydrocarbon with the general formula CnH2n+2

Alkene Unsaturated hydrocarbon with the general formula CnH2n

Cycloalkane

Saturated, ring-shaped hydrocarbon with the general formula CnH2n

Unsaturated molecule

A molecule which contains a C=C double bond.

Saturated molecule

A molecule which does not contain a carbon to carbon double bond.

45Wallace Hall Academy

2020/2021

Addition Reaction When a molecule adds on across the C=C double bond in an alkene.

Hydrogenation An addition reaction in which hydrogen is added.

Homologous Series

A family of molecules with the same general formula and similar chemical properties.

Viscosity The thickness of a liquid; very viscose means very thick.

Flammability How easily a substance burns; very flammable means burns easily.

Fractional Distillation

The process by which crude oil is separated into fractions.

Fraction A group of hydrocarbons with a boiling point range.

Cracking The process by which long, less useful hydrocarbons are broken up into smaller more useful hydrocarbons. Alkenes are produced.

Polymer A long chain molecule made of repeating units.

Monomer A small molecule used to form a polymer.

Gram Formula Mass(GFM)

The mass of one mole of a compound.

46Wallace Hall Academy

2020/2021