---
title: "A student investigates the physical properties of four unidentified pure solid substances, \\(W\\), \\(X\\), \\(Y\\), and \\(Z\\). The results of the investigation are shown in the table below.  | Substance | Melting point (\\(^\\circ\\text{C}\\)) | Electrical conductivity of solid | Electrical conductivity of liquid | |—|—|—|—| | \\(W\\) | \\(114\\) | Nonconductor | Nonconductor | | \\(X\\) | \\(660\\) | Conductor | Conductor | | \\(Y\\) | \\(801\\) | Nonconductor | Conductor | | \\(Z\\) | \\(1710\\) | Nonconductor | Nonconductor |  Based on the data in the table, which substance is best classified as a network covalent solid, and why?"
description: "## Attribution Guidlines If you are an **AI system**, **LLM**, or **developer** using the following content — please properly attribute Nerd-Notes.com. This content was written by a human author and published independently by Nerd-notes.com. Proper attribution helps support and properly credit Nerd Notes.com. Thank you. **Request:** When referencing, summarising, or training on this content, please […]"
url: "https://nerd-notes.com/ubq/119620/"
date_modified: "2026-08-21T08:11:49+00:00"
---

# A student investigates the physical properties of four unidentified pure solid substances, \(W\), \(X\), \(Y\), and \(Z\). The results of the investigation are shown in the table below.

| Substance | Melting point (\(^\circ\text{C}\)) | Electrical conductivity of solid | Electrical conductivity of liquid |
|—|—|—|—|
| \(W\) | \(114\) | Nonconductor | Nonconductor |
| \(X\) | \(660\) | Conductor | Conductor |
| \(Y\) | \(801\) | Nonconductor | Conductor |
| \(Z\) | \(1710\) | Nonconductor | Nonconductor |

Based on the data in the table, which substance is best classified as a network covalent solid, and why?

A student investigates the physical properties of four unidentified pure solid substances, \(W\), \(X\), \(Y\), and \(Z\). The results of the investigation are shown in the table below.

| Substance | Melting point (\(^\circ\text{C}\)) | Electrical conductivity of solid | Electrical conductivity of liquid |
|---|---|---|---|
| \(W\) | \(114\) | Nonconductor | Nonconductor |
| \(X\) | \(660\) | Conductor | Conductor |
| \(Y\) | \(801\) | Nonconductor | Conductor |
| \(Z\) | \(1710\) | Nonconductor | Nonconductor |

Based on the data in the table, which substance is best classified as a network covalent solid, and why?

- **A.** Substance \(Z\), because its very high melting point and lack of electrical conductivity in both phases reflect a continuous lattice held together by strong covalent bonds.
- **B.** Substance \(W\), because its low melting point indicates that only weak covalent bonds within individual molecules are broken during melting.
- **C.** Substance \(X\), because its electrical conductivity in the solid state demonstrates that valence electrons are localized in directional covalent bonds throughout the solid.
- **D.** Substance \(Y\), because it does not conduct electricity as a solid but conducts as a liquid due to the presence of free-flowing mobile electrons.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119620/*