Which statement best describes a physical change?

• A. A process in which the composition of a substance remains unchanged, but its appearance or state may change.
• B. A process in which new substances with different chemical properties are formed.
• C. A change that cannot be reversed by physical means.
• D. A reaction that always produces heat and light.

Answer: (A)

Verified step by step guidance

1. Understand the definition of a physical change: it is a change where the substance's composition remains the same, but its physical properties such as appearance, shape, or state may change.
2. Recognize that in a physical change, no new substances are formed; the molecules or atoms are rearranged but not chemically altered.
3. Contrast this with a chemical change, where new substances with different chemical properties are produced.
4. Note that physical changes are often reversible by physical means, such as melting, freezing, or dissolving, whereas chemical changes usually are not easily reversed.
5. Identify that the statement describing a physical change should emphasize unchanged composition and possible changes in appearance or state without forming new substances.