Lesson video

Hello, my name is Mr. Gundry, and I'm very excited to be learning about graphene and fullerenes with you today.

We are going to go through our understanding of giant covalent structures, specifically allotropes of carbon that we've studied so far, but we're also going to relate this to our understanding of structure, properties, and uses of various different structures as well.

In this lesson, we are going to describe the properties of graphene and fullerenes and relate them back to their structures.

There are some key words that are going to be useful in today's lesson, and they are allotrope, graphene, fullerene, Buckminsterfullerene, and a nanotube.

On the next slide, we can see their definitions, but we're just gonna go through them as we get to them in the lesson.

So this lesson is split into two parts.

We're gonna be looking at graphene specifically on its own to begin with, and then we're gonna study fullerenes and nanotubes in the second half of this lesson.

So just a reminder that diamond and graphite are allotropes of carbon.

Remember, that means that they are different structural forms of the same elements.

These both have a giant structure.

So remember that is a vast network of atoms in a lattice structure where we have a repeating regular structure.

We know graphite is made of layers of hexagonal rings of carbon atoms, but each layer on its own is known as graphene.

Graphene as a single atom-thick layer of carbon is another allotrope of carbon.

Which statement best describes graphene then? Have a read through these kind of responses, and pause the video to have a read through them, and then press play when you are ready to continue.

Okay, so the answer is b.

It is a single layer of carbon atoms arranged in a hexagonal ring-like structure.

It's not three dimensional.

Well, it is, I guess, because the atoms are three dimensional, but if we consider each sheet to be a two-dimensional sheet, but the sheet can be quite vast in how wide and how deep that sheet is.

Like graphite, graphene has a high melting and boiling point due to having a giant structure.

Each carbon atom is bonded to three others in strong covalent bonds, and these bonds, like they do for graphite and for diamond, require large amounts of energy to break to be able to change the state from solid to liquid or gas.

Also like graphite, graphene can conduct electricity, and that's because it has a free delocalized electron for each atom, so those electrons are free to move and therefore carry a charge or current.

So some more statements for you here.

Read through.

Which do you think are true about the bonding structure on properties of graphene? Pause to have a read, and press play when you're ready to continue.

So there are two correct answers here.

It is a and c.

It has a high melting point and can conduct electricity.

Graphene is not made of simple molecules, it's a giant structure, and each carbon atom is only bonded to three others, and that fourth electron that would be used in bonding is used as a delocalized electron through the structure.

True or false? Both graphite and graphene can conduct electricity.

What do you think? Well, the answer is true.

Which of these two statements is the correct justification as to why? Pause the video now to have a read, and press play when you're ready to continue.

Well, the correct answer is a.

Both have delocalized electrons that can move and carry charge.

So b says that graphene has delocalized electrons, but carbon atoms are delocalized in graphite.

That is not true, so the only correct answer there could be is a.

Despite being a one-atom-thick layer then, the atoms are held together still by very strong covalent bonds.

This makes the properties of graphene slightly different to graphite in that because it's only one-atom-layer thick, it's actually quite a flexible structure.

It's quite lightweight in comparison to other materials, and because it's so thin, it's basically transparent, meaning that you can see almost straight through it.

That means it's got lots of excellent practical applications in things like electronics, specifically in flexible electronics.

And we can use it as a way to transfer electricity through a flexible electronic device without impairing our ability to be able to see such a device.

So true or false then? Graphene is a multi-layered structure with each layer held together by weak forces of attraction.

True or false? Well, the answer is false.

You have a read through the justifications, and you tell me what you think is the answer, and when you're ready to continue, just press play.

Graphene only has one layer of carbon atoms, each atom is held together by strong covalent bonds.

Graphite is a multi-layered structure with each layer held together by weak forces of attraction.

So task A, there's some questions on the screen.

I'd like you to pause as you read through them, and they're all about graphene being an allotrope of carbon.

And when you're ready to continue and hear the answers, press play.

Graphene then is an allotrope of carbon.

Remember, allotropes are different structural forms of an element such as graphite and diamond are two different allotropes of carbon, as is the graphene structure that we've looked at today.

You are asked in this question to describe and explain two properties that both graphite and graphene share due to their giant covalent structures.

There are a couple of answers you could have given.

So here are some examples.

So both graphite and graphene share the property of high electrical conductivity due to the presence of delocalized electrons that can move through the structure and carry a charge or current.

Both have a high melting point as all carbon atoms are held together by strong covalent bonds that require large amounts of energy to break.

So in this question, you were asked to describe and explain one property that differentiates graphite and graphene.

And so here are a few examples that you could have given.

They differ in that graphite is a three-dimensional structure with weak forces of attraction between its layers that enables the layers to slide over each other, so it could be used, for example, as a lubricant.

Graphene however, is extremely strong but also flexible due to its two-dimensional structure where all carbon atoms are still directly bonded to three other atoms. So that was the first half of this lesson looking at graphene.

We're now going to look at fullerenes and nanotubes.

They're very similar to what we've looked at with graphene, but they have some slight quirks, which I am really looking forward to sharing with you.

So the first thing we're gonna look at is these fullerenes.

So fullerenes are another allotrope of carbon, and like graphene, are also only one-atom-thick structures.

Because we can define how many atoms there are in the structure, so this example on the screen shows C60, that tells us that there are 60 carbon atoms in the structure.

This means that they are classed as molecules.

These are simple molecular substances.

I have a model pre-made, so you can see here.

I've got another one.

I believe this is C20.

This has only got 20 carbon atoms in the structure.

They're represented by these blue spheres.

That's because of the angle needed to be able to build this structure.

So usually we would use black spheres to represent carbon atoms. So again, slight limitation of the physical model that we are using here.

So C60 specifically is known as Buckminsterfullerene.

It's named after a man called Buckminster Fuller.

He was an architect who designed buildings that looked very similar to these kind of structures.

So Buckminsterfullerene, C60, has a cage-like fused ring structure.

So all fullerenes in fact have a cage-like fused ring structure made of hexagons and pentagons, sometimes even heptagons, so that's a seven-sided shape, resembling a football.

Each of the 60 carbon atoms then are strongly covalently bonded to three others.

So a bit like in graphite and graphene, all carbon atoms are bonded to three others.

You might be thinking, "Well, what does that mean in terms of that extra electron?" And we're gonna cover that in a second.

Some other properties therefore of fullerenes include that it is a black solid, as you might expect.

Carbon generally has kind of a greyish black kind of colouring, but we can actually dissolve this because it's molecular in organic solvents, and it makes a nice violet solution.

You may have come across, or may come across, kind of a nickname for Buckminsterfullerenes, a bit of a mouthful to say, and kind of they're colloquially known as buckyballs.

So what makes fullerenes like C60 different from other allotropes of carbon like diamond, graphite, and graphene? Pause now to have a read through these answers, and then press play when you're ready to move on.

Well, they have delocalized electrons, but so do graphite and graphene, so that doesn't make this difference from them specifically.

They're all composed of carbon atoms. So the only two correct answers here that we have are c and d because all the other structures, diamond, graphite, and graphene, are giant structures, not simple molecules, and they all are kind of either big bulky 3D structures or kind of made of layers of 2D structures.

These are closed cage-like structures, so very different to diamond, graphite, and graphene.

So our C60 is one that we talk about a lot.

Two others, C70 and C84, are also quite stable, and some of these are actually quite regularly found in nature.

These aren't just manmade structures, but they were discovered through manmade laboratory experiments.

C20, as we've already discussed, is the smallest fullerene, but fullerenes can potentially have hundreds or if not thousands of carbon atoms in their structure.

As we've said, they made up of either five or six carbon atom rings, but sometimes they can even have up to seven atoms in that cycle.

As they are simple molecular in nature, they have very low melting and boiling points, so very weak forces of attraction between the molecules fullerenes.

True or false then? Fullerenes like C60 are molecules made up of rings of carbon atoms. What do you think? Well, the answer is true.

And I'd like you to have a pause now to read through the justifications as to why the answer is true.

Well, the answer is true because the structure of fullerenes is based on a hexagonal ring structure of carbon atoms, but potentially also of five or seven atom rings as well.

Part b here says that there is no limit to the number of carbon atoms that can be in one of the ring structures in fullerenes, and that's not true.

There is a limit to how many carbon atoms can be in that ring structure.

So fullerenes have delocalized electrons.

As we've said, there's only three covalent bonds per carbon atom.

There's this one extra electron per carbon atom that's free to move, but due to the molecular form of these substances, they actually don't conduct electricity very well because the electrons can't move between the molecules.

This means these fullerenes cannot conduct electricity.

And you'll notice here that this word has crept in.

It's kind of highlighted in green.

These spherical fullerenes cannot conduct electricity, and that's because there are actually another type of fullerenes that are elongated, and we call these elongated fullerenes nanotubes.

They're a type of fullerene that is cylindrical in nature, and they're effectively just a sheet of graphene rolled into a cylindrical shape.

They've got a very high length to diameter ratio, and therefore also because there's only one carbon atom bonded to three others, so one electron per atom is free to move, they have these delocalized electrons that can move and carry a charge and current.

So true or false? Spherical fullerenes and nanotubes can both conduct electricity due to their delocalized electrons.

True or false? Well, the answer is false, and I'd like you to read through these justifications.

Pause the video now to select one, and then when you're ready to move on, press play.

So the correct answer is that spherical fullerenes are simple molecules.

Simple molecules don't conduct electricity because they can't pass the electrons between the various molecules, whereas nanotubes are very long structures, so they can pass the electrons down the structure.

So nanotubes then.

It's a slightly different diagram here.

A nice moving one.

Nanotubes have a very high tensile strength.

That means that they are resistant to breaking or stretching.

They're very lightweight and they're very flexible, which means that their properties make them very useful for use in things like composites where we take multiple materials and combine them together to make a new material that has a set of desirable properties.

We can use them in specialised materials, or electronics, and nanotechnology because of their small size and ability to conduct electricity.

So which substances below then are made up of one-atom-thick structures of carbon atoms? We've got three choices.

We've got nanotubes, spherical fullerenes, or graphene.

Pause now if you need a bit of time.

Well, the answer is in fact all of them.

All of them are made up of one-atom-thick structures of carbon.

Right, we're now on to our final set of tasks then for you.

So this is the first one we're gonna look at now.

There is a table with some properties.

Structure of these four different allotropes of carbon.

I've completed diamond for you.

I'd like you to now have a go at filling in the blanks using the same sort of language for graphite, graphene, and specifically C60, but more generally, fullerenes.

Pause now whilst you complete this, and press play when you're ready for the answers.

So diamond, graphite, and graphene all have giant covalent structures.

C60 fullerenes, on the other hand, are simple molecules.

We have a defined number of atoms in these spherical fullerenes, whereas for the others, we have an undefined number of atoms and we have this more kind of rigid structure.

We have a regular arrangement, a repeating pattern, which we don't have in simple molecules.

The melting and boiling points of diamond, graphite, and graphene are all very high.

That's because they have these giant structures, large amounts of energy, or relatively large amounts of energy, should I say, are required to break the strong covenant bonds between the atoms to get the state to be changed from liquid to gas or from solid to liquid.

Whereas for fullerenes, we have a relatively low melting and boiling point, and that's because of the simple molecular nature.

There are weak forces of attraction between the molecules that don't require as much energy as giant covalent bonds do to kind of be overcome to turn into either a liquid or gas, depending on whether we are melting or boiling.

Diamond then is an insulator as are fullerenes.

They both do not conduct electricity.

Even though fullerenes have delocalized electrons within the molecules, those electrons are not able to be transferred to other molecules, so they can't conduct electricity.

And again, diamond has no free-moving delocalized electrons, so cannot conduct electricity.

Graphite and graphene do have free-moving delocalized electrons, so can carry charge or a current.

I'm hoping you were paying attention 'cause that's all going to be very useful to you now because for task two, three, four, and five, you need to explain some of these properties and give some descriptions as to why they have the properties that they do.

So if you need a bit of time on this, pause the video now, and when you're ready to move on, press play.

So question two was to explain why cylindrical fullerenes, nanotubes, can conduct electricity, but spherical fullerenes like C60 can't.

Well, cylindrical fullerenes, those carbon nanotubes, can conduct electricity because they have a structure similar to graphene with delocalized electrons free to move along the tube's length.

This allows the flow of an electric current.

Spherical fullerenes however, whilst having delocalized electrons lack an extended structure that allows free electron movement.

They can't move from molecule to molecule.

This prevents them from being able to conduct electricity.

Question three asks you to explain why fullerenes have such different melting points to graphene.

And that's again because fullerenes, whilst they have a very similar structure to graphene in that they have one carbon atom covalently bonded to three other carbon atoms, in graphene, we have a giant structure, whereas fullerenes are made of molecules.

They are discreet closed entities with weak forces of attraction between them.

They require less energy to change state than graphene does because graphene has to have all of the strong covalent bonds between each of the carbon atoms broken.

So significantly large amounts of energy, more than for fullerenes, are required to break the bonds in a giant covalent substance.

Question four asks you to compare the structure and properties of graphene and carbon nanotubes, and discuss how these properties influence the potential uses of nanotubes.

So carbon nanotubes are essentially just a tube of graphene.

Nanotubes are significantly elongated in comparison to their diameter, giving them an exceptional tensile strength.

This structure grants nanotubes high flexibility and resilience, making them ideal for applications that require materials that are both strong and lightweight, such as in composite materials, specialised materials, electronics, and nanotechnology.

And the final question, question five.

Why can spherical fullerenes and graphite both be described as slippery? Well, spherical fullerenes are often described as slippery because of their shape and structure which allows them to roll over each other easily.

This reduces friction, making them useful as lubricants.

Graphite is slippery because its structure consists of layers of carbon atoms arranged in hexagonal rings.

These layers are held together by weak forces of attraction, allowing them to slide over each other with little resistance.

This makes graphite a good lubricant.

So in summary then, graphene is a single layer of graphite, it's very strong, and can conduct electricity.

Fullerenes are molecules of carbon that have a hollow shape, and the structure of fullerenes is based on hexagonal rings of carbon atoms or carbon rings of five or seven atoms. Buckminsterfullerene is a specific spherical fullerene that contains 60 carbon atoms, and a carbon nanotube is a tube of graphene that is very long compared to its diameter and has a high tensile strength.

Well done on your effort in today's lesson.

We've done quite a bit of work today understanding various different types of allotropes of carbon.

We're on our way to fully understanding how allotropes of carbon work and talking about the differences between bonding, structure, and properties.

I look forward to seeing you in the next lesson.