Lesson video

Hello, my name is Mrs. Collins and I'll be guiding you through our learning today.

This lesson is going to be about materials, more specifically, composites, metals, and polymers.

So let's get started.

So welcome to this lesson, which forms part of the unit on materials and is called materials and composites.

Now the materials we're gonna take a look at today are metals, ceramics, and polymers.

And we're gonna have a look at some of their physical properties and then take a look at their uses.

And then we're gonna move on to look at composites.

So here are the key words for today's lesson, which we're going to explore, metal, alloy, ceramic, polymer, and composite.

Now, some of those words will be very familiar to you, but others will be new.

And what might be useful is for you to pause the video at this stage and just take a look at some of those definitions and maybe make a couple of notes.

Now this lesson is divided into two main sections.

We're gonna talk through the different types of materials, first of all, and then we're gonna look and see how we can improve materials afterwards.

So let's make a start on that first part, which is the materials.

Now first of all, it's worth mentioning that everything around you is made of materials, all these different types of materials.

And we can divide materials into two main groups.

So we can say that materials are natural or they're manmade.

So an example of a natural material might be wood, and a manmade material might be something like plastic.

And when we look at these materials, we need to consider their properties, so their physical properties, and then relate them to the uses that we have for those materials.

So let's take a look, first of all, at metals.

So metals are shiny, hard, good thermal and electrical conductors.

And this means they're really useful for things like construction, for jewellery, and even for things like electrical wiring.

So let's have a look in those properties in a little bit more detail and relate them to their uses.

So we'll know that metals are shiny and they're strong, and this makes them really useful for jewellery.

So things like gold, silver, and platinum will be used for jewellery, but metals are also malleable and ductile.

Now malleable means that they can be hammered into shape and ductile means that they can be stretched out into wires.

So copper is really useful for water pipes, for example, because it can be hammered into shape, but is useful for wiring because it's ductile.

But metals are also good thermal and electrical conductors.

So thermal conductors means they're really useful for things like utensils for cooking, but electrical conductors again relates to wiring.

So copper is really useful for electrical wiring because it's a good electrical conductor and it's ductile so it can be stretched out into a wire without breaking.

So here's a question based on what we've just been discussing and I'd like you to consider this question and the answers.

So silver is a metal, what properties would you expect silver to have? So there's a list of four properties there.

Have a read through them and see which ones you would expect silver to have because it's a metal.

I'll just give you a moment to think about it.

So hopefully, you've recognised that silver is both shiny and malleable.

Now remember, malleable means that it can be hammered into shape.

Well done for getting that right.

Now we're gonna move on to ceramics.

Now, ceramics are different because they're hard, brittle heavy and heat-resistant.

Now brittle means that if you drop them, they're likely to break or shatter, but they're also chemically unreactive, which means they're really useful for holding chemicals in the science lab.

So most of the chemicals that you receive when you're carrying out a chemical experiment will be held or housed inside a ceramic.

Now ceramics can be made from lots of different materials, but a couple of examples are clay and that can be used to make pottery.

And then silica, which is found in sand that can be used to make glass.

And ceramics have got lots of different uses.

So we've got bricks, which we're gonna look at in a little bit more detail, tableware, things like cups, plates and mugs and electrical insulators, but we also use them in art as well.

So ceramics are actually made from softer materials, which are then heated to very high temperatures, for example, in a kiln to form the ceramic.

So an example of this would be bricks.

So most houses you see around you will be made of bricks.

And bricks is originally made of clay.

So the clay is moulded into a specific shape, is heated to a very high temperature and that helps the clay to harden.

And because of the way the bonds are between the atoms in ceramics like this, the substances are opaque.

Now glass ceramics are made in a slightly different way.

So they're made by melting sand to again, to a very high temperature and then allowing it to cool and solidify.

And when that substance cools and solidifies, it forms a transparent substance.

And again, this is because of the way the atoms are joined together.

And of course, this makes it really useful for making things like glass window panes or making containers where we want to see the inside of the container itself and see what's inside it.

So again, we've got a question based on that work we've just been discussing.

So we've got a vase there in the image and that is made from a ceramic.

But which of these properties in the list would tell you that that is actually a ceramic? So I'll just give you a moment to read through those four different properties and think about which one means that's a vase is ceramic.

Which property does that vase have that tells you it's a ceramic? So I'll give you a moment to think about it.

So hopefully, you've recognised that it's brittle.

And remember, brittle means that if you were to drop it, it would shatter.

And you know that that's what would happen to a ceramic vase if you were to knock it over.

Okay, let's consider polymers now.

Now plastics are made from polymers and what a polymer is, is a long chain molecule made of lots of smaller molecules all joined together in a big chain.

So here are some examples of polymers, specifically plastics.

And if you look at them, you will recognise they will have different properties.

So not all polymers have the same properties.

So if you have a look at that plastic bottle there and then you've got in the middle, you've got a material, so many of your clothes will be made of polyester.

If you have a look at the label inside them, they will have polyester in them.

And all of those have got different properties to each other.

So for example, the pencil sharpener is quite a stiff plastic, whereas, the plastic used in the bottle is a little bit more flexible.

So polymers can be tailored.

So they can be, you know, different polymers can be used for different purposes.

A flexible rubber, that means you can actually manipulate it and move it around.

And actually, rubber is a natural material all the way through to hard plastics.

So that pencil sharpener was using a hard plastic.

But we know that not all polymers therefore, have got the same properties, but most polymers have these properties.

So they're usually lightweight, durable, flexible, although some are rigid.

So for example, that pencil sharpener was made of a rigid plastic.

They are insulators, they're poor electrical conductors and poor thermal conductors and they're malleable.

And remember, malleable means they can be hammered or manipulated into shape, but some are brittle.

So some of those harder, more rigid plastics are actually brittle.

So if you drop them they would shatter.

Now if we consider a plastic bottle that holds water, they are made from particular types of polymers or plastics that are lightweight, durable, which means that they'll last for quite a long time and flexible and you need them to have those properties in order to use 'em for a plastic water bottle.

Here is a question based on that piece of work.

So how could you find out if similar sized bottles were made from a polymer or ceramic? So have a look at the three different suggestions there and see which ones would work and would help you tell the difference between a polymer or a ceramic.

So A, check to see if there were opaque or transparent.

B, weigh the bottles, the polymer bottle will be lighter or C, drop the bottles, the ceramic will break.

So I'll just give you a moment to think about it.

So let's take a look at the answers.

So B, if you weigh the bottles, the polymer bottle will be lighter.

So polymer is lighter than ceramic.

And then C, the ceramic will break if it's dropped.

So bottles, plastic bottles would not break when dropped, but a ceramic bottle would.

Now we did say that most ceramics were opaque, but we didn't say that most polymers were transparent.

So even though the bottle was transparent and you know, it could be made from glass and glass is a ceramic, remember? So that would be transparent.

So A would be incorrect.

So well done if you got that right.

Okay, so we're now gonna have a go at task A and this is relating to all of the work that we've covered so far.

And it consists of three questions.

We're gonna do question one and two, first of all, and then we're gonna move on to question three.

So question one asks you to match the material to its properties.

So we've got the three different materials that we've discussed today and a list of physical properties that those materials might have.

Now bear in mind, that a property might relate to more than one material.

So brittle for example, might relate to more than one of those different materials and that's okay.

Question two, we've got two plant pots and they've been dropped and plant pot A has smashed and plant pot B has not smashed.

And we need to work out which one is made of ceramic and which one is made of polymer and then justify our answer.

So what I'd like you to do is just pause the video for a moment and think about those questions, answer those questions and I'll see you afterwards and go through the answers.

Welcome back.

So let's have a look at those two different questions then, we'll deal with question one, first of all.

So metals are strong, malleable, good electrical conductors, good thermal conductors, hard and shiny.

Ceramic is brittle and hard.

And polymers, remember, can have lots of different properties depending on the polymer.

So we need to consider all of those in the list.

So polymers are strong, they can be brittle or they can be malleable and they can be hard as well.

So you need to check your answer to that one carefully.

'cause you may have made a mistake there 'cause you're not considered all different types of polymers.

Let's go on to question two.

So for this question, we need to think about plant pot A and plant pot B separately.

And it's worth having a sentence or a couple of sentences for each plant pot to explain what you think your answer is and then justify it.

So plant pot A was made from ceramic.

Ceramics are brittle, so we'll break into pieces when dropped.

Now I want to check your answer.

Have you included the word brittle in your response? Because it's useful to include the key words when we're answering questions like this, so at the actual name of the property.

Then plant pot B was made from polymer.

Many polymers are flexible and malleable, so will not break when dropped.

So have a good look at your answer again.

Have you used the word like flexible or malleable in your response when talking about polymers? Right, well done if you've got those correct.

Let's go on to look at question three.

And this one's a little bit different.

So we've got some pupils looking at two different spoons and what they're doing is they're talking to each other about the properties of those spoons and then seeing if they can work out which one is made of metal and which one is made of polymer.

So they've got a whole different explanations there.

There's four different explanations as to what they think the answers to the question is.

So what you need to do is read through those different suggestions and decide which one is the best suggestion, and then explain your response.

So again, if you want to pause the video, have a go answering the question and then I'll see you when you're finished.

Hello and welcome back.

So hopefully, you came to the conclusion that Andeep actually had the best answer to the question.

And this is because metals are actually good thermal conductors, but polymers are poor thermal conductors.

So placing them in hot water is a good way to tell the difference between the two.

Let's have a look at the other answers and see why they're less good in terms of suggestion.

So let's look at Lucas, first of all.

So Lucas is suggesting bending the materials.

Now some polymer spoons will snap because they're brittle, but remember, not all polymers are brittle.

Some polymers might be malleable.

So even though all metals are malleable, some plastics might be malleable too.

So it's not a good way of telling the difference between the two.

Sophia's answer is also a poor suggestion, but hers is a poor suggestion because she's showing something that is common between the two materials.

So she's saying this property is the same, so we can't use this to tell the difference between the two.

We need to look at a way that they're different to each other, not a way that they're the same as each other.

Then we've got Izzy.

Now, Izzy has an interesting suggestion because we know that metals on the whole are heavier than polymers.

So on the surface it looks like it's a really good answer, but unfortunately, we don't know if the spoons are the same size or not 'cause that's not mentioned in the question.

So and Andeep's answer is better than is his answer.

If the spoons were the same size, then the metal spoon would be heavier, it would have more mass than the plastic spoon.

So we could use it as that suggestion.

So well done if you said Andeep.

Okay, let's go on to the second part of the lesson then, improving materials.

We're gonna start with alloys.

So alloys are mixtures of two or more elements where at least one element is a metal.

So sometimes those other elements might be metals and sometimes they're non-metals.

So let's have a look at brass to start off with.

So brass is actually an alloy of copper and the copper is mixed with zinc, which is an example of another metal.

And the reason why brass is used to make musical instruments is because it's got good acoustic properties.

So that's to do with the sound that it makes when the vibrations are taking place.

So these alloys are made to improve the physical properties of metals.

So they often have more uses than the metals that make up them.

So steel is a really good example.

And steel is an alloy of iron and it contains iron and very specific quantities of carbon and other elements as well.

And steel is stronger and harder and more resistant to corrosion than iron.

So it's more useful than iron for things like construction, it's less likely to rust and it's harder and stronger.

So it's really good for building bridges, but it's also useful in buildings as well.

Let's answer this question then to do with alloys.

So an alloy is a mixture of elements including at least one non-metal.

Is that true or false? And then you need to justify your answer.

So pause the video and have a go answering that question.

Welcome back.

So hopefully, you recognise that that statement is actually false.

And the reason it's false is because an alloy is a mixture of elements with at least one metal, not one non-metal.

So just take care when reading through the questions.

So hopefully, you got that right and well done.

Okay, let's move on to composites then.

So composites combined materials to create a new material and the new material has improved properties.

So a really good example of this is reinforced concrete, and this is used in construction.

So a lot of buildings these days, particularly larger buildings, are made from reinforced concrete rather than just concrete.

And reinforced concrete is a composite material and it's made from pouring concrete around steel rods or mesh.

So in other words, it's a composite of concrete and steel and it is much stronger than concrete because the steel itself increases the strength when the material stretched and the concrete increases the strength when the material is squashed.

So the composite includes the best properties of those two different materials and combines them together.

So modern tennis rackets are made from another type of composite called carbon fibre.

Old tennis rackets used to be made from wood or aluminium, but carbon fibre is much better than these other materials.

And this is because it's lightweight and strong, but also it means that the strings can be pulled to a much higher tension and this means that tennis balls can be hit at a higher speed.

Okay, let's have a go at answering a question then, relating to composites.

So which of the following materials are a composite? So what you need to do is read through each of those different substances and decide which one is a composite.

Pause the video now and I'll see you when you're finished.

Welcome back.

So hopefully, you realise that chipboard is an example of a material which is a composite.

And it's composite because it's made with wood and glue together.

And also fibreglass is another example of a composite because it consists of glass bonded together with resin.

Now solder is an example of an alloy because it's a metal combined with another substance.

And then in this case, two metals combined together.

So let's have a go at task B, which relates to the second part of this lesson on improving materials.

So we're gonna do question one first of all, and then we're gonna move on to question two.

So question one has got three parts to it.

So first of all, it asks you for the difference between an alloy and a composite.

It asks you to circle different materials that are alloys and then it asks you to name a composite material.

So what I'd like you to do is pause the video here, answer the questions, and then I'll see you afterwards to go through the answers.

Welcome back.

So let's have a look at the answers to this first question then.

So question A asks for the difference between an alloy and a composite.

So an alloy is a mixture of two or more elements where at least one is a metal.

And a composite material is made from two or more different types of material.

When combined, they create a new material with improved properties, and that's true of alloys and composite materials.

Then it asks you to circle the materials that are alloys.

So bronze and steel are both alloys.

Fibreglass and wood chip are both examples of composite materials.

So in C, it says name a composite material.

So you could have put fibreglass or wood chip, but there are others as well that were mentioned in the lesson like carbon fibre.

Well done if you got the answers to that correct.

Let's move on to question two and we're gonna do 2a and 2b.

So let's have a go at 2a, first of all.

So reinforced concrete is made from steel and concrete.

What properties will reinforced concrete have, you're gonna put a tick in the last column.

So now we're moving on to question two and we're gonna have a look at question 2a to start off with.

And this says reinforced concrete is made from steel and concrete, what properties will reinforced concrete have? So you're going to put a tick in the last column for the properties that you think reinforced concrete will have.

So pause the video here and answer the question.

So part B is asking you to give a reason for your answer to part A.

So again, pause the video, answer the question, and then we'll go through the answers.

Let's have a look at the answer to question 2a.

What properties will reinforce concrete have? We're gonna put a tick in the last column, strong when it's squashed.

And strong when it's stretched.

It's going to be durable and it's gonna be strong when it's heated.

And then the reason why that's correct, reinforced concrete is a composite material, composites combine or take on the properties of the materials that make up the composite.

The steel will be covered by concrete, so it will not rust or lose strength quickly in a fire.

So it's important to remember that it's a composite material, so it will take on the properties of the materials that form it.

So well done if you got that correct.

So let's move on to question three.

Wood is very strong when it's stretched along the grain, but not very strong when it's stretched across the grain.

Now the grain are those lines that you see in wood.

So if you look at wood, you'll see lines on the surface of the wood.

And if you're going along with the lines that's going along with the grain.

So the question says, which board will make the strongest floor? Who do you agree with and why? So again, read through those particular statements made by the four different students.

See which one you agree with and explain your answer.

Pause the video here and have a go answering the question.

Welcome back.

So hopefully, you recognise that Sophia this time had the correct answer.

And this is because the plywood is glued together at right angles.

So the grain is pointing in two different directions, so it makes it strong in both directions.

Now, Lucas was incorrect because the grain is in random directions and that means it won't be strong.

Izzy suggested natural wood, and this is not strong across the grains that's actually written in the question.

And then Andeep suggested chipboard would be stronger.

But again, we got the issue over the random directions.

So hopefully, you got that correct and well done if you did.

So here is a summary of today's lesson.

So metals are good thermal and electrical conductors.

They are strong, shiny, malleable, and ductile.

And remember, malleable means they can be hammered into shape and ductile means that they can be stretched into a wire.

Ceramics are made from soft substances becoming hard and brittle when heated.

Plastics are made from polymers, and there are many different types of plastic with different properties.

And alloy is a mixture of elements including at least one metal and composites combined materials to create a new material with improved properties.

So thank you very much for joining me for today's lesson.