Graphene and fullerenes — AQA GCSE Combined Science
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Graphene and fullerenes explained
Graphene is a single layer of graphite, one atom thick, in which carbon atoms are arranged in a hexagonal lattice.
Read the full explanation
Each carbon atom forms three covalent bonds, leaving delocalised electrons that can move across the layer. This makes graphene an excellent conductor of electricity and thermal energy, and it is also very strong and flexible. These properties make it useful in electronics, for example in fast transistors, touchscreens and conductive films, and in composites, where it is added to materials such as plastics to increase strength and conductivity without adding much mass. A useful method is to link each property to an application: high electrical conductivity leads to electronics, and high strength with low mass leads to composite materials.
Students should be able to explain the properties of graphene in terms of its structure and bonding.
Graphene is a single layer of graphite, one atom thick, in which each carbon atom is covalently bonded to three others in a flat hexagonal lattice. The fourth outer electron per atom is delocalised across the layer, so graphene conducts electricity and thermal energy well. Because the layer is only one atom thick, it is transparent and extremely light. Graphene has a very high melting point and is insoluble in water because of the strong covalent bonds within the layer, which require a large amount of energy to break. For example, graphene can be used in touchscreens because it conducts while remaining transparent, and in composite materials where strength with low mass matters.
Fullerenes are molecules of carbon atoms with hollow shapes. The structure of fullerenes is based on hexagonal rings of carbon atoms but they may also contain rings with five or seven carbon atoms. The first fullerene to be discovered was Buckminsterfullerene (C₆₀) which has a spherical shape.
Fullerenes are molecular forms of carbon with hollow cage-like shapes. Their frameworks are built mainly from hexagonal rings of carbon atoms, but pentagonal or heptagonal rings can also be present, which allows the sheet to curve and close into a hollow shape. Buckminsterfullerene, C₆₀, was the first fullerene discovered; it contains 60 carbon atoms arranged in a sphere resembling a football, with each carbon bonded to three others. Because fullerenes are molecules, they have weak forces between separate molecules, so they have relatively low melting points compared with giant covalent carbon structures such as diamond. Their hollow cages can enclose other atoms or ions, which makes them useful in drug delivery and as catalysts.
Carbon nanotubes are cylindrical fullerenes with very high length to diameter ratios. Their properties make them useful for nanotechnology, electronics and materials.
Carbon nanotubes are a form of fullerene in which carbon atoms bond in a seamless cylinder, often imagined as a rolled-up sheet of graphene. Because the tube is only nanometres wide but can be micrometres long, its length to diameter ratio is very high, giving an enormous surface area for its mass. The delocalised electrons along the carbon framework allow tubes to conduct electricity and heat, while the strong covalent carbon-carbon bonds make them stiff and very strong yet low in density. These combined properties explain their use in nanotechnology, in electronics such as nanoscale wiring or components, and in materials such as lightweight composites for sports equipment or vehicles.
recognise graphene and fullerenes from diagrams and descriptions of their bonding and structure
Graphene is a giant covalent form of carbon, whereas fullerenes are simple molecular forms. In graphene, each carbon atom bonds covalently to three others, forming a single sheet one atom thick of interlocking hexagons; the fourth electron is delocalised, allowing electrical conductivity. Fullerenes are closed cage molecules of carbon atoms, typically with hexagonal and pentagonal rings. Buckminsterfullerene, C₆₀, is a hollow sphere of 60 carbon atoms. While each carbon atom in a fullerene also forms three covalent bonds, fullerenes are simple molecular because they form discrete, finite molecules rather than a continuous giant lattice. To recognise them, note the overall shape: a flat sheet indicates graphene, while a closed sphere or cylinder indicates a fullerene.
give examples of the uses of fullerenes, including carbon nanotubes.
Fullerenes are carbon molecules with closed cage or tube structures, and their properties lead to specific uses. Buckminsterfullerene, C₆₀, is a hollow sphere that can trap atoms or small molecules inside its cage, so it is investigated for drug delivery, as a lubricant and as a catalyst. Carbon nanotubes are cylinders of hexagonal carbon rings, often just nanometres wide. They have a very high strength-to-weight ratio, conduct electricity and heat well, and have a large surface area, so they are used to reinforce composite materials such as sports equipment and aircraft parts, in nanoscale electronics and sensors, and in hydrogen storage. When answering, name the fullerene, state a property and link it to the use, for example nanotubes are strong and light, so they reinforce tennis rackets and bicycle frames.
Your focus
- Describe graphene as a single layer of graphite with a hexagonal lattice.
- Explain how the structure of graphene gives it high electrical conductivity and strength.
- Relate the properties of graphene to its uses in electronics and composites.
Show all 18 objectives
- Describe the structure of graphene as a single layer of graphite one atom thick.
- Relate the bonding and delocalised electrons in graphene to its strength, conductivity, transparency and low mass.
- Apply knowledge of graphene's properties to justify a named use such as touchscreens or composite materials.
- Describe fullerenes as hollow molecular forms of carbon based on hexagonal rings with possible five- or seven-membered rings.
- Identify Buckminsterfullerene as C₆₀, the first fullerene discovered, and describe its spherical shape.
- Explain how the molecular structure of fullerenes affects their physical properties and suggest a use such as drug delivery.
- Describe the cylindrical structure of carbon nanotubes and their very high length to diameter ratio.
- Relate the properties of carbon nanotubes, including conductivity and strength, to their bonding and nanoscale structure.
- Explain how the properties of carbon nanotubes make them useful in nanotechnology, electronics and materials.
- Identify graphene from a diagram or description as a single hexagonal sheet of carbon atoms one atom thick.
- Identify fullerenes, including C₆₀ and carbon nanotubes, from diagrams or descriptions as closed cage or cylindrical carbon molecules.
- Explain how the discrete, finite molecular structure distinguishes fullerenes from the continuous giant covalent lattice of graphene.
- State at least two uses of fullerenes, including carbon nanotubes, such as drug delivery, lubricants, composites, electronics and hydrogen storage.
- Link each named use to a property of the fullerene, such as hollow cage shape, high strength, low mass, electrical conductivity or large surface area.
- Distinguish uses of fullerenes from uses of other carbon allotropes such as diamond and graphite.
Graphene and fullerenes exam tips
Marking Points
- Graphene is a single layer of graphite, one atom thick.
- It consists of carbon atoms arranged in a hexagonal lattice, with each carbon atom bonded to three others.
- Delocalised electrons are present and can move across the layer, so graphene conducts electricity well.
- Graphene is very strong and flexible, which makes it useful in composites.
- Its high electrical conductivity and nanoscale thickness make it useful in electronics.
- Graphene has a very large surface area per unit mass, which can be useful in composite materials and sensors.
- Graphene is a single layer of graphite that is one carbon atom thick.
- Each carbon atom forms three covalent bonds to other carbon atoms, giving a flat hexagonal lattice.
- Each carbon atom contributes one delocalised electron, so graphene conducts electricity and thermal energy.
- The strong covalent bonds within the layer give graphene a very high melting point and great strength.
- The one-atom-thick layer makes graphene transparent and very light, which suits uses such as touchscreens and composites.
- Properties must be linked to structure and bonding, not simply listed.
- Fullerenes are molecules made only of carbon atoms and have hollow shapes.
- Their frameworks are based on hexagonal rings of carbon atoms.
- Rings with five or seven carbon atoms may also be present, allowing curvature and closure of the cage.
- Buckminsterfullerene, C₆₀, was the first fullerene discovered and has a spherical shape.
- C₆₀ contains 60 carbon atoms, each bonded to three others, forming a football-like cage.
- Fullerenes are simple molecular substances, so weak forces between molecules give relatively low melting points.
- Carbon nanotubes are fullerenes shaped as cylinders, formed from carbon atoms bonded in a curved hexagonal network.
- They have a very high length to diameter ratio, meaning they are extremely long relative to their nanometre-scale width.
- Delocalised electrons within the carbon structure allow nanotubes to conduct electricity and thermal energy.
- Strong covalent bonds between carbon atoms give nanotubes high tensile strength and stiffness while their low mass keeps them lightweight.
- Their nanoscale dimensions and large surface area make them suitable for nanotechnology applications.
- These properties make nanotubes useful in electronics, for example in tiny circuits or conductive components, and in materials such as strong, light composite materials.
- Graphene is a single layer of carbon atoms, one atom thick, arranged in a regular hexagonal lattice.
- Each carbon atom in graphene forms three covalent bonds to other carbon atoms, leaving one delocalised electron per atom, which allows graphene to conduct electricity.
- Fullerenes are molecules of carbon in closed cages or tubes, containing hexagonal rings and often pentagonal rings; buckminsterfullerene has the formula C₆₀ and a hollow spherical shape.
- Carbon nanotubes are cylindrical fullerenes formed from rolled sheets of hexagonal carbon rings.
- Fullerenes are simple molecular substances with weak intermolecular forces between discrete molecules, unlike the continuous giant covalent lattice of graphene.
- Recognition from a diagram requires identifying the overall shape: a flat sheet for graphene, or a closed sphere or cylinder for a fullerene.
- Buckminsterfullerene, C₆₀, has a hollow cage structure that can trap other atoms or molecules, so it is used in drug delivery systems and as a catalyst.
- Carbon nanotubes are very strong and have a low mass, so they are used to reinforce composite materials such as sports equipment and aircraft components.
- Carbon nanotubes conduct electricity and heat, so they are used in nanoscale electronic circuits, sensors and conductive composites.
- Carbon nanotubes have a very large surface area relative to their volume, so they are used in hydrogen storage and in catalysis.
- Fullerenes can act as lubricants because their spherical molecules can roll over one another, reducing friction between surfaces.
- A full answer names a specific fullerene or nanotube use and links it to a property such as cage shape, strength, conductivity or surface area.
Examiner Tips
- 💡Always state that graphene is one layer of graphite before describing its properties.
- 💡Link each property to a named use, for example high conductivity to electronics and high strength to composites.
- 💡Use comparative language such as very strong, flexible and conductive to make the link between structure and application clear.
- 💡Always name the bond type and the number of bonds per carbon atom when explaining a property.
- 💡Link each property to a specific use, such as transparency plus conductivity for touchscreens.
- 💡Use comparative language such as 'one atom thick' and 'very high melting point' to show scale and strength.
- 💡Quote the formula C₆₀ and state that it contains 60 carbon atoms when asked about Buckminsterfullerene.
- 💡Use the phrase 'hollow shape' and mention hexagonal rings plus possible five- or seven-membered rings.
- 💡Contrast fullerenes with diamond and graphite in terms of molecular versus giant covalent structure when comparing properties.
- 💡Link each property directly to a named use, for example electrical conductivity to electronics and high strength with low density to composite materials.
- 💡Use comparative language such as very high length to diameter ratio and nanometre scale to show understanding of size.
- 💡Sketch a simple cylinder of hexagons if a diagram is requested, and label the tube shape and carbon bonding.
- 💡When a diagram is given, identify the overall shape—flat sheet, closed sphere, or cylinder—before deciding whether the structure is graphene or a fullerene.
- 💡If asked to compare, state one similarity, such as carbon atoms joined by covalent bonds, and one difference, such as graphene being a giant covalent structure while fullerenes are simple molecular.
- 💡Learn at least three uses with their linked properties: drug delivery with the hollow cage, composites with high strength and low mass, and electronics with electrical conductivity.
- 💡Use the phrase carbon nanotubes rather than just nanotubes when the question asks about fullerenes, so the examiner can credit the example.
- 💡If the question says give examples, write two or three distinct uses, each with a brief property link, rather than one long description.
Common Mistakes
- Describing graphene as many layers of graphite: correct this by stating that graphene is a single layer, one atom thick.
- Saying graphene is an electrical insulator because it is covalent: correct this by explaining that delocalised electrons make it a good conductor.
- Confusing graphene with a fullerene such as buckminsterfullerene: correct this by noting that graphene is a flat single layer, while fullerenes are hollow molecular cages.
- Saying graphene is a molecule of carbon: correct this by describing graphene as a giant covalent structure or single layer of graphite.
- Stating that graphene has a low melting point due to weak intermolecular forces: correct this by noting that a single graphene sheet has strong covalent bonds throughout, requiring substantial energy to break.
- Claiming graphene does not conduct because carbon is a non-metal: correct this by explaining that delocalised electrons from the fourth outer electron of each carbon atom carry charge.
- Describing fullerenes as giant covalent structures: correct this by stating they are simple molecules with weak forces between molecules.
- Saying C₆₀ contains 60 carbon atoms joined by 60 bonds: correct this by noting each carbon forms three bonds, so the number of bonds differs from the number of atoms.
- Stating that fullerenes contain only hexagonal rings: correct this by including the possibility of five- or seven-membered rings that create the hollow curved shape.
- Describing nanotubes as molecules with a fixed small formula rather than as very large covalent structures of carbon; correct this by stating they are giant covalent fullerene structures.
- Confusing nanotubes with graphene sheets or with spherical fullerenes such as buckminsterfullerene; correct this by stressing the cylindrical, tube shape.
- Claiming nanotubes are weak because they are thin; correct this by explaining that strong covalent bonding along the tube gives high strength despite the tiny diameter.
- Describing graphene as a three-dimensional giant lattice like diamond: correct this by stating graphene is a single two-dimensional sheet one atom thick.
- Stating that each carbon atom in graphene or a fullerene forms four covalent bonds: correct this by counting three bonds per carbon atom, with the remaining electron delocalised.
- Classifying fullerenes as giant covalent structures: correct this by explaining that fullerenes are simple molecular substances made of discrete, finite cage or tube molecules.
- Giving a use without linking it to a property: correct this by always adding because plus the relevant property, such as nanotubes are strong and light, so they are used in bicycle frames.
- Confusing fullerenes with diamond or graphite uses such as cutting tools or pencils: correct this by naming buckminsterfullerene or carbon nanotubes specifically.
- Claiming that fullerenes are used as fuels or that they melt at low temperatures: correct this by describing uses based on cage shape, strength, conductivity or surface area.