Which of the following most likely indicates that a chemical change has occurred?

• A. Formation of a gas when two substances are mixed
• B. Dissolving sugar in water
• C. Breaking a piece of glass into smaller pieces
• D. Melting of ice into liquid 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. - Dissolving sugar in water is a physical change because the sugar molecules disperse but do not change chemically.
4. - Breaking a piece of glass into smaller pieces is a physical change because the glass's chemical structure remains the same.
5. - Melting of ice into liquid water is a physical change because it involves a phase change without altering the chemical identity of H2O.
6. - Formation of a gas when two substances are mixed indicates a chemical change because a new substance (gas) is produced, showing a chemical reaction has occurred.