Which statement best describes the difference between physical changes and chemical changes?

• A. Physical changes do not form new substances, while chemical changes do.
• B. Physical changes form new substances, while chemical changes do not.
• C. Both always form new substances.
• D. Neither involves any change in matter.

Answer: (A)

The key idea is whether a new substance is created. In a physical change, the material changes form or state but keeps the same chemical identity; ice turning into water, or sugar dissolving in water, simply changes arrangement or dispersion, not what the substance is. In a chemical change, bonds are broken and new bonds form, so you end up with substances with different properties—rust forming from iron, burning wood producing ash and gases. Because it directly describes whether a new substance appears, the statement that physical changes do not form new substances while chemical changes do is the best description.