---
title: "A student compares the physical properties of two Group 14 oxides, \\(\\text{CO}_2\\) and \\(\\text{SiO}_2\\), recorded in the table below.  | Substance | Molar mass (\\(\\text{g/mol}\\)) | Melting point (\\(^\\circ\\text{C}\\)) | | :— | :— | :— | | \\(\\text{CO}_2\\) | \\(44.01\\) | \\(-78.5\\) (sublimes) | | \\(\\text{SiO}_2\\) | \\(60.08\\) | \\(1710\\) |  Which of the following statements best explains the large difference in melting points between \\(\\text{CO}_2\\) and \\(\\text{SiO}_2\\)?"
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url: "https://nerd-notes.com/ubq/119772/"
date_modified: "2026-08-21T08:12:17+00:00"
---

# A student compares the physical properties of two Group 14 oxides, \(\text{CO}_2\) and \(\text{SiO}_2\), recorded in the table below.

| Substance | Molar mass (\(\text{g/mol}\)) | Melting point (\(^\circ\text{C}\)) |
| :— | :— | :— |
| \(\text{CO}_2\) | \(44.01\) | \(-78.5\) (sublimes) |
| \(\text{SiO}_2\) | \(60.08\) | \(1710\) |

Which of the following statements best explains the large difference in melting points between \(\text{CO}_2\) and \(\text{SiO}_2\)?

A student compares the physical properties of two Group 14 oxides, \(\text{CO}_2\) and \(\text{SiO}_2\), recorded in the table below.

| Substance | Molar mass (\(\text{g/mol}\)) | Melting point (\(^\circ\text{C}\)) |
| :--- | :--- | :--- |
| \(\text{CO}_2\) | \(44.01\) | \(-78.5\) (sublimes) |
| \(\text{SiO}_2\) | \(60.08\) | \(1710\) |

Which of the following statements best explains the large difference in melting points between \(\text{CO}_2\) and \(\text{SiO}_2\)?

- **A.** \(\text{SiO}_2\) has a much higher melting point than \(\text{CO}_2\) because \(\text{SiO}_2\) forms discrete molecules whose larger, more polarizable electron clouds result in significantly stronger London dispersion forces than those in \(\text{CO}_2\).
- **B.** \(\text{SiO}_2\) has a much higher melting point than \(\text{CO}_2\) because \(\text{SiO}_2\) is an ionic crystal lattice held together by strong Coulombic attractions between \(\text{Si}^{4+}\) and \(\text{O}^{2-}\) ions, whereas \(\text{CO}_2\) is a molecular solid.
- **C.** \(\text{SiO}_2\) has a much higher melting point than \(\text{CO}_2\) because melting \(\text{SiO}_2\) requires breaking strong covalent \(\text{Si}-\text{O}\) bonds throughout a three-dimensional network solid, whereas phase changes of \(\text{CO}_2\) require overcoming only weak London dispersion forces between discrete molecules.
- **D.** \(\text{CO}_2\) has a much lower melting point than \(\text{SiO}_2\) because the intramolecular \(\text{C}=\text{O}\) double bonds in \(\text{CO}_2\) are weaker and more readily cleaved by thermal energy than the \(\text{Si}-\text{O}\) single bonds in \(\text{SiO}_2\).

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119772/*