---
title: "A pure substance is heated at a constant pressure of \\(1.0\\text{ atm}\\) by a heat source supplying energy at a constant rate. The heating curve for a \\(1.00\\text{ mol}\\) sample of the substance is shown in the graph. Based on the graph, which of the following statements is correct?"
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url: "https://nerd-notes.com/ubq/121422/"
date_modified: "2026-08-23T05:02:11+00:00"
---

# A pure substance is heated at a constant pressure of \(1.0\text{ atm}\) by a heat source supplying energy at a constant rate. The heating curve for a \(1.00\text{ mol}\) sample of the substance is shown in the graph. Based on the graph, which of the following statements is correct?

A pure substance is heated at a constant pressure of \(1.0\text{ atm}\) by a heat source supplying energy at a constant rate. The heating curve for a \(1.00\text{ mol}\) sample of the substance is shown in the graph. Based on the graph, which of the following statements is correct?

![A 2D line graph showing a heating curve with light gray gridlines. The horizontal x-axis is labeled Heat Added (kJ) with tick marks and numerical values at 0, 10, 20, 30, 40, 50, and 60. The vertical y-axis is labeled Temperature (°C) with tick marks and numerical values at -20, 0, 20, 40, 60, 80, and 100. A single continuous solid black line connects five line segments in order: a slanted line from (0, -20) to (5, 0); a flat horizontal line from (5, 0) to (12, 0); a slanted line from (12, 0) to (32, 60); a flat horizontal line from (32, 60) to (56, 60); and a slanted line from (56, 60) to (60, 100). No other particles, labels, text, or annotations appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1787461331-UqoGPh.jpg)

- **A.** The substance has a greater specific heat capacity in the gas phase than in the liquid phase because the gas phase has a steeper slope.
- **B.** The enthalpy of fusion is greater than the enthalpy of vaporization because melting occurs at a lower temperature than boiling.
- **C.** The enthalpy of vaporization is greater than the enthalpy of fusion because more heat is required to boil the liquid than to melt the solid.
- **D.** The average kinetic energy of the molecules increases during the phase change at \(60^\circ\text{C}\) because heat continues to be added to the sample.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/121422/*