AQA A-Level Chemistry Paper 3, 2021: Question 14
1 mark · Easy difficulty · Multiple Choice
Melting and Covalent Bonding This question tests your understanding of what happens at the molecular level when different types of substances melt. You are asked to identify which substance involves the breaking of covalent bonds during melting, rather than just intermolecular forces.
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Question text
14 In which substance do covalent bonds break when it melts?
[1 mark]
A hexane
B ice
C iodine
D silicon dioxide
Mark scheme
Show the mark scheme
14 D 1 silicon dioxide
How to answer it
In which substance do covalent bonds break when it melts?
A) Hexane
Hexane is a simple molecular substance. When it melts, intermolecular forces (London forces) break — not covalent bonds within molecules.
Hexane is a simple molecular substance. When it melts, intermolecular forces (London forces) break — not covalent bonds within molecules.
B) Ice
Ice is also molecular. Hydrogen bonds (intermolecular forces) break when it melts, but the covalent O–H bonds inside water molecules remain intact.
Ice is also molecular. Hydrogen bonds (intermolecular forces) break when it melts, but the covalent O–H bonds inside water molecules remain intact.
C) Iodine
Iodine consists of I2 molecules. The melting process breaks weak van der Waals forces — again, not covalent bonds within I2.
Iodine consists of I2 molecules. The melting process breaks weak van der Waals forces — again, not covalent bonds within I2.
D) Silicon dioxide
SiO2 is a giant covalent structure. To melt it, you must overcome strong covalent bonds throughout the lattice — these are actual covalent bonds breaking, making this the correct answer.
SiO2 is a giant covalent structure. To melt it, you must overcome strong covalent bonds throughout the lattice — these are actual covalent bonds breaking, making this the correct answer.
Topics
Physical Chemistry · 3.1.3 Bonding
Question and mark scheme from the AQA A-Level Chemistry examination, Paper 3, 2021. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.