Which statement best describes a chemical change?

• A. Formation of a new substance with color change or gas formation.
• B. Dissolving a solid in water.
• C. Change in state from solid to liquid.
• D. Mixing two substances with no reaction.

Answer: (D)

Chemical change happens when substances react to form a new substance with properties that are different from the starting materials. The clearest signs are the formation of a new substance, often shown by a color change, the evolution of a gas, or the appearance of a precipitate. In these statements, the description that mentions a new substance and includes color change or gas formation is the one that truly describes a chemical change. Dissolving a solid in water is a physical change because the substance’s identity doesn’t change and it can often be reversed. Changing state from solid to liquid is melting, another physical change. Mixing two substances with no reaction is simply combining materials without forming something new, which is also a physical change.