Lesson video

Hello, I am Mrs. Adcock.

Welcome to today's lesson on addition polymerization.

We are going to be looking at what are addition polymers and how are they made.

Today's lesson outcome is, I can describe the formation of an addition polymer from its monomer.

Some of the keywords that we will be using in today's lesson include polymers, monomers, relative molecular mass, addition polymerization and repeating unit.

Here you can see those keywords used in a sentence.

It would be a good idea to pause the video now and read through those sentences, or you might like to make some notes so that you can refer back to them later on in the lesson.

Today's lesson is broken down into two main sections.

The first section is on addition polymers, and then we are going to move on to look at monomers, polymers and the repeating unit.

Let's get started on addition polymers.

Polymers are substances with a high average relative molecular mass.

Now remember, relative molecular mass is the sum of all the relative atomic masses of the atoms in a molecule and polymers have a high average relative molecular mass, because they are made up of many small molecules and these small molecules are called monomers.

So it's the monomers that join together to make polymers.

Alkenes can be used as monomers to make polymers, and alkenes are a homologous series of compounds that contain a carbon, carbon double bond.

So the carbon, carbon double bond of alkenes opens up and this allows monomers to join together and we've got an image there of an alkene, and that's an alkene with two carbon atoms, so that's ethene, so we've got an ethene molecule and that double bond in ethene can open up and then lots of ethene molecules could join together to make a polymer.

Time for a check for understanding.

Polymers are made from joining together, A, monomers, B, monoxides or C, monoatomic.

Polymers are made from joining together.

Small molecules called monomers, so well done if you selected, A, monomers.

Monomers can be represented in different ways.

We can see an image of a monomer here and here's another monomer and there's a final image of a monomer.

These images all show the same monomer.

They are just represented in different ways, and if you look carefully at all of them, you can see that their longest carbon chain is four carbons long, and therefore these monomers are all molecules of butene.

In addition polymerization, the monomers all contain a carbon, carbon double bond and addition polymerization is a type of polymerization where all of the monomers contain a carbon, carbon double bond and we end up just making one product and that product is our polymer.

Examples of monomers used in addition polymerization include these two molecules that you can see here and you will notice that they both contain a carbon, carbon double bond.

Time for another check for understanding.

Which of the following could be a monomer used in addition polymerization? Now there may be more than one answer that's correct, so choose any of those options that you think could be used as a monomer in addition polymerization.

The correct answers are A and B, because both A and B contain the carbon, carbon double bond that all are monomers contain in addition polymerization.

Molecule C does not contain a carbon, carbon double bond.

Monomers join together to produce polymers, so we can see lots of monomers there.

They are the small molecules that join together to produce our polymer and here is a section of a polymer chain, and we can see that the monomer has a carbon, carbon double bond and this opens up and then these monomers have joined together to produce a polymer.

Here is an example of a section of an addition polymer and only one product, and that's the polymer is made during addition polymerization, because all that happens is that double bond opens up and the monomers join together.

So there's no other product other than the addition polymer that is made.

Time for a question to check we've understood that.

What is produced when an addition polymer is formed from monomers? Do we make A, the polymer and water, B, the polymer and carbon dioxide, or C, only the polymer? <v ->The correct answer is C, only the polymer.

</v> So during addition polymerization we only make one product and that product is the polymer.

When naming polymers, we use the word poly followed by the monomer name in brackets.

For example, the monomer styrene makes the polymer polystyrene.

If we have a look at some more examples here, we've got the monomer ethene, so that will make polyethene and the ethene is in brackets, we have the monomer in brackets.

Chloroethene will make polychloroethene and there we've got the polymer, polytetrafluoroethene and the monomer for that would've been tetrafluoroethene.

Polypropene is made from which monomer? Is polypropene made from A, propanol, B, propene or C, propionic acid? The correct answer is B, propene.

So polypropene is a polymer, and when we name polymers, we have poly and then the name of the monomer, so the mono in this case would've been propene.

Well done if you got that correct, you're clearly focusing well today.

Time for our first practise task of today's lesson.

You need to complete the table below.

So you've got the names of some monomers and you've got the names of some polymers, and you need to complete the table to fill in the name of the missing polymers and monomers.

If you pause the video now, have a go at filling in that table and then come back when you're ready to go over the answers.

Let's have a look how you on.

Butane is a monomer and the polymer that, that makes will be called polybutene.

Dichloroethene will make the polymer, polydichlorinoethene and the polymer, polystyrene is made from the monomer, styrene and the polymer, polyvinyl acetate is made from the monomer, vinyl acetate and finally, tetrafluoroethene will make the polymer, polytetrafluoroethene.

Well done if you correctly word out the names of those polymers and monomers.

You're doing really well.

Let's move on.

So we've had a look at what addition polymers are.

Now we are going to focus a little bit more on drawing monomers, polymers and the repeating unit.

So let's move on to the second part of our lesson.

Chemical equations for polymerization reactions show the monomer and the polymer.

Here we can see the monomer and how that monomer forms a polymer.

We put n before the monomer and n represents any number.

So we could have any number of monomer units that join together to form our polymer, and there are often hundreds of thousands of monomers in a polymer chain.

If you have a look at the polymer, you will notice that we have opened up the double bond and those bonds are sticking out of the edge of brackets that we put around our polymer and then we put an n to show that we've got n number of monomers in our polymer.

The unit that repeats in a polymer is known as the repeating unit, and we can see a section here of a polymer chain and there we've got highlighted one repeat unit.

So it's this unit that is repeating in our polymer.

Here is an example showing together the structures of a monomer, a polymer, and the repeating unit.

Here's our monomer.

The monomer contains the carbon, carbon double bond.

Here's our polymer.

Now we've opened up that double bond, we've added brackets, and we've added an n to show there are n number of monomers in our polymer.

Here is the repeating unit.

It is this section that repeats throughout the polymer chain.

So we've taken our monomer and we've opened up the double bonds and we've gained our repeating unit.

The repeating unit contains open bonds on either side, and this shows it's bonded to further repeat units.

Which of the following represents a polymer? Well done, if you chose B.

B represents a polymer.

So we've got the repeating unit, it's got brackets around it, and we've got n to show that we have got n number of monomers in our polymer.

Which of the following shows a monomer? Well done if you chose answer A.

A is a monomer.

It's got the carbon, carbon double bond, and it's our small molecule that joins together to form our polymer.

Hopefully you noticed that B shows the polymer, and we've got the brackets with an n on the outside, and C shows the repeating unit.

We are going to look now at how we can draw the polymer produced from a monomer, and I'll show you an example and then it'll be your turn to have a go.

So we've got a monomer there and we want to draw the polymer, so we need to open up the double bond to show the repeating unit.

You can see that there on the bottom of your screen and then we are gonna add brackets and an n to indicate the number of repeat units in the polymer.

So we started with the monomer and now we've drawn a polymer.

So you're turn to have a go, draw the polymer produced from this monomer.

If you pause the video and have a go at answering this question.

Hopefully you opened up the double bond to show the repeat unit, added brackets and added an n and your polymer should look like this.

Well done if you got that one correct.

Now we are going to do it the other way round, where we're going to draw the monomer that produced this polymer.

So the first thing we want to do is identify the repeating unit, and then once we've got the repeating unit, we can reform the carbon, carbon double bond to help us gain the monomer that produced the polymer.

So there at the bottom of the screen, you can see the monomer that was used to produce that polymer.

Your turn to have a go, if you pause the video now and then draw the monomer that produced this polymer.

Hopefully you identified the repeating unit and then you reformed the carbon, carbon double bond to draw a monomer like this.

Well done if you got that one correct.

You're doing really well in today's lesson.

Time for our final practise task of today's lesson.

The first thing that you need to do is complete the table that you can see here.

So you're going to have to draw a repeat unit in the first row, and then in the second row, you've been given the repeat unit and you need to draw the monomer and the polymer structures.

So pause the video now and then have a go at answering question one.

Before we go over the answers, we've got a second part to this task and you need to complete the table below with the monomer structure, the polymer structure, and the repeat unit.

If you pause the video now and then have a go at answering question two, when you come back, we will go over the answers to both question one and question two.

I'll see you in a moment when you're ready to go over the answers.

Let's go over the answers.

So for the first one, you needed to draw the repeat unit, so you should have opened up the double bond and hopefully your repeat unit will look like that.

Then for the second row, you were given the repeat unit and you needed to draw the monomer by closing up and reforming that double bond and then the polymer structure will look like the repeat unit, but it's got brackets and an n and for question two, the monomer will have the carbon, carbon double bond and the repeat unit, this time you would've removed the brackets and the n from the polymer structure and for the last row, your polymer should look like that and here's your repeat unit.

So hopefully you've got all those questions correct.

Well done if you did.

We have reached the end of today's lesson on addition polymerization.

We first of all looked at addition polymers, and then we've just looked at monomers, polymers and the repeating unit and how we draw those structures.

Let's summarise the key points from today's lesson.

A polymer is a substance of high average, relative molecular mass, made up of small repeating units and we know those small repeating units are called monomers and the reason the polymer has a high average relative molecular mass is because we have hundreds of thousands of monomers often in a polymer.

In addition polymerization, only one molecule is formed, and we know that molecule is the polymer.

So for example, addition polymerization of ethene forms polyethylene.

So when we name polymers, we put poly, and then we put the name of the monomer in brackets.

Polymers have a specific displayed formula to show repeat units.

When we draw polymers, we put brackets around the repeating unit and we put an n.

A polymer's monomer can be deduced from its structure and vice versa.

Addition polymers can be made by combining together a variety of mono molecules, containing that carbon, carbon double bond.

You have worked really well in today's lesson, so well done.

I've really enjoyed today's lesson, and I hope you have too and hope that you're able to join me for another lesson soon.