Which of the following best describes a physical change?

• A. A change in the state or appearance of a substance without altering its chemical composition.
• B. A process in which new substances with different chemical properties are formed.
• C. A transformation that involves breaking chemical bonds and forming new ones.
• 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 involves a change in the state or appearance of a substance without altering its chemical composition.
2. Recognize that physical changes include processes like melting, freezing, boiling, dissolving, or changes in shape or size, where the substance remains chemically the same.
3. Contrast physical changes with chemical changes, which involve breaking and forming chemical bonds to create new substances with different properties.
4. Identify that options describing the formation of new substances or reactions producing heat and light refer to chemical changes, not physical changes.
5. Conclude that the best description of a physical change is a change in the state or appearance of a substance without altering its chemical composition.