Which of the following sets of procedures and observations indicates a chemical change?

• A. Dissolving table salt (NaCl) in water
• B. Mixing vinegar and baking soda, resulting in bubbling and gas formation
• C. Breaking a glass window into smaller pieces
• D. Heating copper metal until it glows red, then cooling it to room temperature

Answer: (B)

Verified step by step guidance

1. Understand the definition of a chemical change: it involves a process where substances react to form new substances with different properties, often accompanied by observable signs such as gas formation, color change, temperature change, or precipitate formation.
2. Analyze each option to identify if a new substance is formed or if only physical changes occur:
3. 1. Dissolving table salt (NaCl) in water is a physical change because the salt dissociates into ions but no new substance is created.
4. 2. Mixing vinegar and baking soda produces bubbling and gas formation, indicating a chemical reaction where new substances (carbon dioxide gas, water, and a salt) are formed.
5. 3. Breaking a glass window into smaller pieces is a physical change because the composition of the glass remains the same.
6. 4. Heating copper metal until it glows red and then cooling it is a physical change involving a change in temperature and possibly phase, but no new substance is formed.
7. Conclude that the set of procedures and observations indicating a chemical change is the mixing of vinegar and baking soda, as it produces gas and new substances.