Which of the following would indicate that a new substance has been formed during a chemical reaction?

• A. The substance is dissolved in water.
• B. A color change occurs that cannot be reversed by physical means.
• C. The substance is crushed into smaller pieces.
• D. The temperature of the substance increases when heated.

Answer: (B)

Verified step by step guidance

1. Understand that a chemical reaction results in the formation of a new substance with different properties from the original substances.
2. Recognize that physical changes, such as dissolving in water, crushing into smaller pieces, or heating to increase temperature, do not create new substances but only change the physical state or form.
3. Identify that a color change which cannot be reversed by physical means suggests a chemical change because it indicates a change in the substance's chemical composition.
4. Recall that irreversible changes in color, formation of gas, precipitate, or energy changes often signal a chemical reaction has occurred.
5. Conclude that among the options, the irreversible color change is the best indicator that a new substance has been formed during the chemical reaction.