﻿Hello there, my name is Mr. Robbins, and welcome to the Structures and Bonding lesson on Polymers. Now all you're going to need is a pen and some paper. If you can put your phone on silent, pop it out of the way, that'll really help you concentrate. Now it's important that you stick with it to the end, this topic, I think once you get the hang of it, it's actually really easy. So I think we can finish this topic with full mastery by the end of our lesson. Let's get started. Here's an outline of today's lesson. We're going to talk through some of the uses of polymers. We're going to introduce you to the concept of what a polymer is, how they're made, and then we're going to try and pull everything together and link those properties back to the uses, so it all makes sense. Let's get started. Polymers are basically everywhere, wherever you're working right now, if you look around, you will find some polymers. Here's some examples. When you go to school, you wear a school uniform, most school uniforms have an aspect of manmade fibres. Those manmade fibres are polymers. Plastics are polymers, so everything made of plastic, from toys to cutlery to all sorts of different things are polymers. Food and polymers are closely linked together. Many polymers are used in the packagin' of food to help preserve it and stop it from going off and spoiling so quickly. These are just some of the examples of how polymers impact modern life. You can see why it's so important that we learn about them. This is what a polymer is. A polymer is a long-chain molecule made of many repeating units. Can you pause the video now and write that in your book, please? We tend to use analogies or models to understand complex ideas, here are two possible models that you could use to help you understand what a polymer is. On the left we've got beads, each bead is a repeated unit that goes again, and again, and again, the entire necklace, that's a polymer. Each bead is the repeating unit, and the string is the bond that links them together. Or you may prefer a train, a long train like this train here. Each carriage is a repeated unit again, and again, and again, and again, that's the same, and the link between them is that carriage thing that holds them on. I suppose the disadvantage of the train is that you normally have one engine at the front that's pulling everything along, that's not the same as the rest, but apart from that, it makes a lot of sense. Let's introduce these words to you then, so let's break down the word polymer. First of all, poly means many, and mer means unit, or units in this case, so polymer means many units. If you look at the picture down here, you can see we have this very repeated structure going across. Polymers are made of repeated units, and those repeated units are called monomers. Can you say monomers with me in three? One, two, three, monomers. Mono means one, and mer means unit, again, same word, same meaning. So what we've got is one repeated unit here, I've put a box around it. You can see that that is the bit that repeats again and again and again. We've got one, two, three, four, five, six, probably seven repeated units on the screen there. So the monomer is just that box, and the polymer is the long-chain molecule that's made of many, many of them joined together. So, what I've got for you now is a little video that shows you how to draw polymers and monomers, and some of the conventions. You don't have to write anything down now. Watch it carefully, and in a minute, we'll do some quick questions to check you understand. Polymers are made of monomers, so let's start by drawing the simplest monomer. This monomer is a hydrocarbon 'cause it's made of only Carbon and Hydrogen. It has this characteristic double bond in the middle of it, which means it's made up of two pairs of electrons that are shared in here. It's got four hydrogens around it, it's got two carbons. So it's name starts with a eth beginning, and it's an alkene, so it's got an e-n-e, so it's called Ethene. It's the monomer. Now when monomers react, what they do is, their double bond breaks, and it forms a single bond and two kind of half bonds. And then what would happen is another monomer would come along here. I'm just drawing it a bit smaller, so I can fit it on easily. And it's double bond will break, so that forms a single bond there, and then another half bond sticking out the end here. So this is a single bond in here. We've got this kind of half bond here and half bond here, and then you can think of other monomers joining on at both ends and spreading along, along, along in both directions. Now, if you were given a question, where it asked you to draw Polyethene, then you'd be drawing thousands of these all in a row, and that would be really, really, really, really boring and take a long time. So good old scientists always come up with shorthand ways of doing things that don't need to be drawn fully, so let's go back to our monomer, let's go back to Ethene like this. So in science and maths, there's a convention. If you use the letter n what you mean is a big number, big number. So n is a big number, so if you think of a big number then double that, and that's the kind of number we're thinkin' of. Okay, big number. And what they say is, when we get a large number or a big number of monomers, they all bond together. They form a polymer, but that polymer has a repeating unit, and that repeating unit is similar to this monomer. So they say, let's just draw the monomer, how it is when it reacts. What does this repeated unit look like? And now this has been multiplied many, many times, so we're going to put brackets around it like we do in maths, and we're going to put a little n down in the bottom corner. Do you remember how we have H two for hydrogen? So the small number down to the right tells me how many I've got. So we've got n lots of this, that's why the n goes down there. Now this polymer is made of Ethene, so we call it Polyethene, Polythene is sometimes what people call it. This is what those cheap plastic bags are made of. The monomer was Ethene, the polymer was Polyethene. All we've done is we've taken the n, put it down there. We've broken the double bond and made these two bonds that go past the brackets, and we've put it in brackets. We've drawn exactly the same atoms or groups bonded to the carbon, so that's just copied across, and we've successfully drawn our polymer repeating unit. It's simple. Here's a quick recap of what we went for in the video. You'll see the end and the beginning of the monomer and the double bond. There it is. And then the polymer, you'll see the brackets, and the single bonds going out the outside of each bracket, very important. If they have to be really long in the exams, if you're starting here, and they go that long, that's fine, as long as they go outside your brackets. And then they've got the n in the corner. Now remember that number n means many. Now the way I teach my students in my classroom to remember this is to remember the phrase brackets and bonds. Okay, so when drawing a polymer, you remember brackets and bonds. You do your brackets, you make sure your bonds go outside the bracket, and you put your little n in the corner, and that's all you need to do. Notice the Cs and the Hs stay exactly the same. So, time for a quick check, look carefully at my polymer, pause the video and choose the correct monomer. Unpause when you're ready, and I'll tell you the answer. Made your choice? Good, let's find out if you're right. If you choose B, you are correct, well done. Notice how it has the C H three and the C H three, and it has formed a double bond, and the brackets are gone. Here's another one. Again, pause the video, make your choice, and then unpause when you're ready, good luck. What did you pick? A, B, no you picked C, didn't you? I can tell, I can tell you picked C. Well done. Now C and the polymer are slightly different because it's C H three and H three C, but they're the same elements bonded in the same way. They're just written from opposite directions, so don't be put off by that. Look for the elements and see how they're bonded. Now, time for something a little bit different. Here you're going to pause the video, and you're going to draw me the polymer from this monomer. Okay, so pause the video now, and in your book draw me the polymer. Don't ever forget brackets and bonds, brackets and bonds, off you go. Here we go. Did you get the right answer? Single bonds, brackets and bonds, an n in the corner, the C l and the C H three. Make sure it's all identical to this one. Make sure you've got your capital letters as well. No lower case hs, please, let's not get sloppy now. We're doin' this too long. Here's another one, slightly different, don't be put off. Have a go, good luck. Ready for the answer, three, two, one. See how it follows exactly the same pattern. We've got C, C, Fs above, Fs are below, brackets and bonds, job done. Now polymers can be represented as these bead models. You can see down here, we have these models of beads. Each chain is a polymer chain, and each bead is a monomer. This has been simplified like a particle diagram, and what you can see here is they're all kind of overlapping each other like this and across there. Now, one of the things that's really interesting about polymers is the polymer's properties and the monomer's properties are normally completely different. Let's take a good old fashioned plastic bag. That's called Polyethene bag, it's made of the monomer, Ethene. Ethene is a gas at room temperature, yet Polyethene can hold your vegetables from the supermarket, so clearly they have very, very different properties. Why is that though? Why could one thing that's a long chain of the other thing be so different? Have a quick think about what we've been doing so far on this topic and see if you can come up with any answers, unpause the video when you're ready. So the reason is all to do with the weak forces of attraction. Remember, we've been talking about them, those forces that are between the covalent molecules. These are covalent molecules. They're very long covalent molecules, but they're still covalent molecules. They behave exactly the same way, so they've got a weak force of attraction. So when these layers crossover, you haven't got stronger forces of attraction, you've got exactly the same strength, but you've got a lot more of them. Okay, got a lot more weak forces of attraction. We can change the language now slightly, and we can use the phrase intermolecular forces if we want to. Weak forces of attraction is completely fine, but intermolecular forces is also allowed, and you can use those two interchangeably when you're talking about covalent molecules. So, polymers have got higher melting points than the monomers because they have a lot more intermolecular forces between the long-chain molecules. I'm going to go away for a second. Four options here, pause the video, read the question and pick the answer you think best. Unpause when you're done, and we'll go through the answer, good luck. Have you made your choice? Ready for the answer in three, two, one. It's option three, Polyethene has long chains that have a lot more weak forces of attraction between them. Notice they don't have stronger attractions, they have a lot more weak forces, or we could have said intermolecular forces, that would have been completely fine as well. So we've got some uses of polymers here. They can be easily shaped. They can be rigid or flexible, and they can be resistant to chemicals. And these properties affect their uses. I'm back again. If things can be easily shaped, think of your plastics. In fact, plastic means change shape, so plastics are really easy to shape. Consider these clothes pegs, very easy to make this shape. Another material you can make a clothes peg out of is wood, much harder to shape the wood. Much more wood needed to make the peg. So the plastics are incredibly easy to shape, you can just mould them into any shape you want. Think about all the fabrics that are made out of plastics and polymers. Look at this camping picture here, not only is the sleepin' bag, and the tent, and the insulation in the sleepin' bag made out of polymers, the frame that the canvas tent, that the tent goes on, that rigid frame is also made out of polymers. So in that case, they're very rigid. Different polymers have different properties. And they're resistant to chemical attack. Now, in my job, that means we use them to store corrosives, like acids, but in everyday life, that means they're used on the inside of drinks cans, on the inside of fruit juice cartons, to package all sorts of materials, so that they are resistant to chemical attack, both from the elements outside and the product on the inside. It keeps everything fresh and in good condition. So we're coming to the end of the lesson now, let's recap what we've learned today. Polymers are long-chain molecules made from monomers. Think of that train analogy or that necklace analogy, the beads are the monomer, and the long necklace was the polymer. Polymers are everywhere, from what you wear to what you're usin', if you've used a pen, that's a polymer. It's crazy where they are. Polymers have really high melting points 'cause they have many, many weak forces of attraction, or we call them intermolecular forces. There we are, polymers done and dusted. I told you it wasn't that difficult once you get the hang of it. Now, polymers is an area that's quite a small part of the course, people often forget about it. So I'm glad you did this lesson because it means you'll be able to do these questions well, if you get asked them by your teacher. Now it's important that you keep practicin', so make sure you hit next and do the quiz. And I'll see you next time, take care.

This lesson will introduce the concept of polymers. You will be able to draw the displayed formula of monomers and polymers and link the structures to their properties.

Draw the formation of polymers given the monomer

Chemistry

Y10 Chemistry

Key Stage 4

Year 10

Polymers

Bonding, structure and the properties of Matter

UNIT

Ionic bonding introduction

Further ionic bonding

Properties of ionic compounds

Covalent bonding

Simple covalent molecules

The giant covalent structures

Giant covalent structures: Graphene

Review (Part 1)

Metallic bonding

Solids, liquids and gases

Nanoparticles (Triple Chemistry only)

Review (Part 2)

Which of these is the correct ionic formula for Potassium Sulfide? (Hint: Potassium forms a +1 ion and Sulfur forms a -2 ion)

What happens when Calcium (Ca) reacts with Iodine (I)?

What is the definition of a covalent bond?

What is a molecule?

What are the properties of simple covalent molecules? Tick three boxes.

Why do covalent molecules have low melting and boiling points?

What types of elements form covalent bonds?

How is a covalent bond normally drawn?

What element are fullerenes made from?

Why is graphene so good at conducting electricity?

Why is graphene so hard to melt?

What does molten mean?

Why do ionic compounds not conduct electricity as solids?

Why do ionic substances conduct electricity when molten or in solution?

What type of bond links the monomers together when they form a polymer?

What is the correct name of the polymer made from ethene?

What is an Ion?

What happens when Barium (Ba), in group 2, reacts with oxygen (O) which is in group 6?

Which of these substances forms giant covalent substances? Tick all that apply.

Why do giant covalent substances have high melting and boiling points?

What are the properties of diamond? Tick all that apply.

What are the properties of graphite? Tick all that apply.

Which of these state symbols is for when a substance is dissolved in water?

Which one of these is a limitation of the particle model?

How big are nanoparticles?

What is one of the concerns with nanotechnology?

Which type of bonding is positive metal ions in a 'sea' of delocalised electrons?

What is an alloy?

Why are alloys often preferred over pure metals?

Rust forms when iron reacts with oxygen to for iron oxide. What type of bonding would you expect iron oxide to have?

Lesson overview:Polymers

Core Content

Pupils Will Learn

Bonding, structure and the properties of Matter: