Which of the following is an indicator that a chemical change has occurred?

• A. Formation of a precipitate
• B. Breaking a glass into pieces
• C. Change in state from solid to liquid
• D. Dissolving of salt in water

Answer: (A)

Verified step by step guidance

1. Understand the difference between physical and chemical changes. A physical change affects the form of a substance but not its chemical composition, while a chemical change results in the formation of one or more new substances with different properties.
2. Analyze each option to determine if it represents a physical or chemical change:
3. 1. Breaking a glass into pieces is a physical change because the glass's chemical composition remains the same.
4. 2. Change in state from solid to liquid (melting) is a physical change since the substance's chemical identity does not change.
5. 3. Dissolving salt in water is a physical change because the salt dissociates into ions but no new substance is formed.
6. 4. Formation of a precipitate indicates a chemical change because it involves the creation of a new solid substance from a solution, signaling a chemical reaction.