Which of the following best describes how chemical changes differ from physical changes?

• A. Chemical changes involve changes in temperature, while physical changes do not.
• B. Chemical changes are always reversible, while physical changes are always irreversible.
• C. Chemical changes result in the formation of new substances with different chemical properties, while physical changes do not alter the chemical identity of a substance.
• D. Chemical changes only affect the state of matter, while physical changes change the chemical composition.

Answer: (C)

Verified step by step guidance

1. Understand the definitions: A physical change affects the form or physical properties of a substance without changing its chemical identity, such as changes in state (solid, liquid, gas), shape, or size.
2. Recognize that a chemical change results in the formation of one or more new substances with different chemical properties and compositions, indicating a change in the substance's chemical identity.
3. Evaluate the options by comparing these definitions: check if the option correctly distinguishes chemical changes by the formation of new substances and physical changes by the absence of such changes.
4. Note that changes in temperature can accompany both physical and chemical changes, so temperature change alone is not a definitive criterion.
5. Conclude that the best description is the one stating that chemical changes produce new substances with different chemical properties, while physical changes do not alter the chemical identity of the substance.