---
title: "A student investigates the changes that occur during two separate mixing procedures conducted in insulated containers at \\(25.0\\text{ }^\\circ\\text{C}\\), as summarized in the table below.  | Experiment | Procedure | Observations | | :— | :— | :— | | 1 | A \\(10.0\\text{ g}\\) sample of \\(\\text{NH}_4\\text{NO}_3(s)\\) is added to \\(100.0\\text{ g}\\) of distilled \\(\\text{H}_2\\text{O}(l)\\). | The solid dissolves completely; the temperature of the mixture decreases to \\(17.2\\text{ }^\\circ\\text{C}\\); no gas is evolved. | | 2 | A \\(10.0\\text{ g}\\) sample of \\(\\text{NaHCO}_3(s)\\) is added to \\(100.0\\text{ g}\\) of \\(1.0\\text{ M}\\ \\text{HC}_2\\text{H}_3\\text{O}_2(aq)\\). | Vigorous bubbling occurs; the solid dissolves completely; the temperature of the mixture decreases to \\(17.2\\text{ }^\\circ\\text{C}\\). |  Which of the following statements and justifications best explains whether each experiment represents a physical change or a chemical change?"
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url: "https://nerd-notes.com/ubq/123712/"
date_modified: "2026-09-28T12:02:06+00:00"
---

# A student investigates the changes that occur during two separate mixing procedures conducted in insulated containers at \(25.0\text{ }^\circ\text{C}\), as summarized in the table below.

| Experiment | Procedure | Observations |
| :— | :— | :— |
| 1 | A \(10.0\text{ g}\) sample of \(\text{NH}_4\text{NO}_3(s)\) is added to \(100.0\text{ g}\) of distilled \(\text{H}_2\text{O}(l)\). | The solid dissolves completely; the temperature of the mixture decreases to \(17.2\text{ }^\circ\text{C}\); no gas is evolved. |
| 2 | A \(10.0\text{ g}\) sample of \(\text{NaHCO}_3(s)\) is added to \(100.0\text{ g}\) of \(1.0\text{ M}\ \text{HC}_2\text{H}_3\text{O}_2(aq)\). | Vigorous bubbling occurs; the solid dissolves completely; the temperature of the mixture decreases to \(17.2\text{ }^\circ\text{C}\). |

Which of the following statements and justifications best explains whether each experiment represents a physical change or a chemical change?

A student investigates the changes that occur during two separate mixing procedures conducted in insulated containers at \(25.0\text{ }^\circ\text{C}\), as summarized in the table below.

| Experiment | Procedure | Observations |
| :--- | :--- | :--- |
| 1 | A \(10.0\text{ g}\) sample of \(\text{NH}_4\text{NO}_3(s)\) is added to \(100.0\text{ g}\) of distilled \(\text{H}_2\text{O}(l)\). | The solid dissolves completely; the temperature of the mixture decreases to \(17.2\text{ }^\circ\text{C}\); no gas is evolved. |
| 2 | A \(10.0\text{ g}\) sample of \(\text{NaHCO}_3(s)\) is added to \(100.0\text{ g}\) of \(1.0\text{ M}\ \text{HC}_2\text{H}_3\text{O}_2(aq)\). | Vigorous bubbling occurs; the solid dissolves completely; the temperature of the mixture decreases to \(17.2\text{ }^\circ\text{C}\). |

Which of the following statements and justifications best explains whether each experiment represents a physical change or a chemical change?

- **A.** Experiment 1 represents a chemical change, whereas Experiment 2 represents a physical change, because the breaking of ionic bonds in \(\text{NH}_4\text{NO}_3(s)\) constitutes a chemical reaction, whereas the bubbling in Experiment 2 simply reflects the physical release of dissolved gas.
- **B.** Experiment 1 represents a physical change, whereas Experiment 2 represents a chemical change, because the ions in Experiment 1 retain their chemical identities and solid \(\text{NH}_4\text{NO}_3\) can be recovered by evaporation, whereas Experiment 2 produces new chemical substances with different properties, including \(\text{CO}_2(g)\).
- **C.** Experiment 1 represents a physical change, whereas Experiment 2 represents a chemical change, because Experiment 1 involves breaking only intermolecular attractions rather than ionic bonds, whereas the temperature drop in Experiment 2 provides conclusive evidence that a chemical reaction occurred.
- **D.** Both Experiment 1 and Experiment 2 represent chemical changes because both processes result in a measurable decrease in solution temperature and involve the separation of ions from their original crystal lattices.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/123712/*