Which of the following is common to all chemical changes?

• A. No energy change involved
• B. Change in physical state only
• C. Formation of new substances with different properties
• D. Reversibility without altering chemical composition

Answer: (C)

Verified step by step guidance

1. Understand that a chemical change involves a transformation where the original substances are converted into new substances with different chemical properties.
2. Recognize that energy changes (either absorption or release) often accompany chemical changes, but the presence or absence of energy change is not a defining feature common to all chemical changes.
3. Note that a change in physical state (such as melting or boiling) is a physical change, not a chemical change, because the chemical composition remains the same.
4. Consider reversibility: some chemical changes are reversible, but many are not, so reversibility is not a universal characteristic of chemical changes.
5. Conclude that the key feature common to all chemical changes is the formation of new substances with different properties, which distinguishes chemical changes from physical changes.