AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
Substances that consist of giant covalent structures are solids with very…
Full specification wording
Giant covalent structures: Substances that consist of giant covalent structures are solids with very high melting points.
A giant covalent structure is a network of atoms joined by covalent bonds throughout the whole substance.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 1 of 5
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
A giant covalent structure is a network of atoms joined by covalent bonds throughout the whole substance. Examples include diamond, silicon dioxide and graphite. Because the covalent bonds are strong and extend in three dimensions, melting the substance requires breaking many strong covalent bonds, not just overcoming intermolecular forces. This means giant covalent substances are solids with very high melting points. For example, diamond melts at over 3500 °C and silicon dioxide melts at about 1700 °C. Graphite also has a very high melting point because its carbon atoms are held in layers by strong covalent bonds. The high melting point is therefore a consequence of the strong covalent bonding throughout the giant structure, not of intermolecular forces between separate molecules.
What earns the marks
- Giant covalent structures consist of atoms joined by covalent bonds throughout the structure.
- The covalent bonds in a giant covalent structure are strong.
- Melting requires breaking many strong covalent bonds.
- Giant covalent substances are solids with very high melting points.
- Examples include diamond, silicon dioxide and graphite.
Common mistakes and how to put them right
Saying that giant covalent substances have high melting points because of strong intermolecular forces.
Put it right by stating that the strong covalent bonds throughout the giant structure must be broken.
Confusing giant covalent structures with simple molecular substances.
Put it right by noting that simple molecular substances have weak intermolecular forces and low melting points, while giant covalent substances have strong covalent bonds throughout.
Stating that all covalent substances have low melting points.
Put it right by giving diamond or silicon dioxide as a counterexample with a very high melting point.
Exam tips
- Name a specific giant covalent substance, such as diamond or silicon dioxide, to support your explanation.
- Use the phrase 'strong covalent bonds throughout the structure' rather than referring to intermolecular forces.
- Link the high melting point to the energy needed to break many covalent bonds, not to the mass of the substance.
Try the lesson
The start of the Giant covalent structures: Substances that consist of giant covalent structures are solids with very high melting points. lesson, made from checked teaching notes for this specification point.
Have a go first
What is the melting point of a substance that consists of a giant covalent structure?
Listen
A giant covalent structure is a network of atoms joined by covalent bonds throughout the whole substance. Examples include diamond, silicon dioxide and graphite. Because the covalent bonds are strong and extend in three dimensions, melting the substance requires breaking many strong covalent bonds, not just overcoming intermolecular forces. This means giant covalent substances are solids with very high melting points. For example, diamond melts at over 3500 °C and silicon dioxide melts at about 1700 °C. Graphite also has a very high melting point because its carbon atoms are held in layers by strong covalent bonds. The high melting point is therefore a consequence of the strong covalent bonding throughout the giant structure, not of intermolecular forces between separate molecules. A strong answer earns marks for these points. Giant covalent structures consist of atoms joined by covalent bonds throughout the structure. The covalent bonds in a giant covalent structure are strong. Melting requires breaking many strong covalent bonds. Giant covalent substances are solids with very high melting points. A common slip: Saying that giant covalent substances have high melting points because of strong intermolecular forces. Instead, stating that the strong covalent bonds throughout the giant structure must be broken. Exam tip: Name a specific giant covalent substance, such as diamond or silicon dioxide, to support your explanation.
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Key words
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Giant covalent structures
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Covalent bonding
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Melting points
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See every definition
- Giant covalent structures
- A network of atoms joined by covalent bonds throughout the whole substance.
- Covalent bonding
- Bonds that join the atoms throughout a giant covalent structure and are strong.
- Melting points
- Very high for giant covalent substances because melting requires breaking many strong covalent bonds.
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