AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
Students should be able to explain the properties of graphite in terms of…
Full specification wording
Graphite: Students should be able to explain the properties of graphite in terms of its structure and bonding.
Graphite is a giant covalent structure in which each carbon atom forms three covalent bonds to three other carbon atoms, producing layers of hexagonal rings with no covalent bonds between the layers.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 3 of 4
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Graphite is a giant covalent structure in which each carbon atom forms three covalent bonds to three other carbon atoms, producing layers of hexagonal rings with no covalent bonds between the layers. Within a layer the covalent bonds are strong, so graphite has a very high melting point because many strong covalent bonds must be broken. Between layers there are only weak forces, so the layers can slide over one another, making graphite soft and slippery and useful as a lubricant and in pencil leads. One electron from each carbon atom is delocalised, so graphite conducts electricity and is used for electrodes.
For example: Graphite conducts electricity but diamond does not, because in diamond all outer electrons are localised in bonds.
What earns the marks
- Links the high melting point of graphite to many strong covalent bonds within the layers.
- Explains softness and slipperiness in terms of weak forces between layers allowing them to slide.
- Explains electrical conductivity in terms of delocalised electrons, one per carbon atom.
- States that there are no covalent bonds between the layers.
- Compares graphite with diamond, noting that graphite conducts but diamond does not.
Common mistakes and how to put them right
Saying graphite melts easily because layers slide.
Put it right by stating the strong covalent bonds within layers give a very high melting point.
Saying graphite conducts because of free ions.
Put it right by stating delocalised electrons carry the charge.
Saying graphite is soft because covalent bonds break.
Put it right by stating weak forces between layers allow sliding without breaking covalent bonds.
Exam tips
- Structure your answer property by property, linking each to a structural feature.
- Use the contrast between strong covalent bonds within layers and weak forces between layers.
- Mention delocalised electrons explicitly when explaining electrical conductivity.
Try the lesson
The start of the Graphite: Students should be able to explain the properties of graphite in terms of its structure and bonding. lesson, made from checked teaching notes for this specification point.
Have a go first
Which statement describes the structure of graphite?
Listen
Graphite is a giant covalent structure in which each carbon atom forms three covalent bonds to three other carbon atoms, producing layers of hexagonal rings with no covalent bonds between the layers. Within a layer the covalent bonds are strong, so graphite has a very high melting point because many strong covalent bonds must be broken. Between layers there are only weak forces, so the layers can slide over one another, making graphite soft and slippery and useful as a lubricant and in pencil leads. One electron from each carbon atom is delocalised, so graphite conducts electricity and is used for electrodes. For example, graphite conducts electricity but diamond does not, because in diamond all outer electrons are localised in bonds. A strong answer earns marks for these points. Links the high melting point of graphite to many strong covalent bonds within the layers. Explains softness and slipperiness in terms of weak forces between layers allowing them to slide. Explains electrical conductivity in terms of delocalised electrons, one per carbon atom. States that there are no covalent bonds between the layers. A common slip: Saying graphite melts easily because layers slide. Instead, stating the strong covalent bonds within layers give a very high melting point. Exam tip: Structure your answer property by property, linking each to a structural feature.
Key words
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Giant covalent structures
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Delocalised electrons
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Electrical conductivity
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Structure-property relationships
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See every definition
- Giant covalent structures
- Graphite is one of these, in which each carbon atom forms three covalent bonds to three other carbon atoms, producing layers of hexagonal rings.
- Delocalised electrons
- One electron from each carbon atom is delocalised, so graphite conducts electricity and is used for electrodes.
- Electrical conductivity
- Graphite conducts electricity because of delocalised electrons, whereas diamond does not because all outer electrons are localised in bonds.
- Structure-property relationships
- Within a layer the covalent bonds are strong, giving a very high melting point, while between layers there are only weak forces, so the layers can slide over one another.
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