Carbon and silicon are both in Group 4. Each element forms a dioxide.
Carbon dioxide, CO2\mathrm{CO_{2}}CO2, turns from solid to gas at −78 ∘C-78\,^\circ\mathrm{C}−78∘C. Silicon dioxide, SiO2\mathrm{SiO_{2}}SiO2, melts at 1710 ∘C1710\,^\circ\mathrm{C}1710∘C.
A student says, "This shows that the bonds between silicon and oxygen atoms are much stronger than the bonds between carbon and oxygen atoms."
Which response to the student is correct?
The student is correct, because more energy is needed to change the state of silicon dioxide.
The student is incorrect, because silicon dioxide is an ionic compound, not a covalent one.
The student is incorrect, because the covalent bonds in carbon dioxide break when it turns into a gas, but those in silicon dioxide do not.
The student is incorrect, because the difference is caused by structure: melting giant covalent silicon dioxide breaks strong covalent bonds, but carbon dioxide only needs weak intermolecular forces overcome.
60 exam-style questions on OCR GCSE Chemistry 2.3 Properties of materials, covering 2.3.1 Carbon bonding and the variety of organic compounds, 2.3.2 Diamond, graphite, fullerenes and graphene, 2.3.3 Bond strength, changes of state and predicting states, 2.3.4 Bulk properties and types of bonding, and 2.3.5 Nanoparticles: scale, surface area, uses and risks. Each one has a worked solution and a mark scheme showing where the marks go.