Which of the following is the best indication that a chemical change has occurred?

• A. The substance changes from a solid to a liquid.
• B. The temperature of the substance increases when heated.
• C. The material is broken into smaller pieces.
• D. A new substance with different properties is formed.

Answer: (D)

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 indicates a physical or chemical change: For example, changing from solid to liquid is a physical change because the substance's chemical identity remains the same.
3. Recognize that an increase in temperature or breaking a material into smaller pieces are physical changes since they do not alter the chemical composition of the substance.
4. Identify that the formation of a new substance with different properties is the hallmark of a chemical change, as it implies a chemical reaction has occurred.
5. Conclude that the best indication of a chemical change is when a new substance with different properties is formed, distinguishing it from physical changes.