Which observation best indicates that a change is a physical change rather than a chemical change?

• A. The substance changes state, but its chemical composition remains the same.
• B. Heat is released and a precipitate forms.
• C. Gas bubbles are produced and a color change occurs.
• D. A new substance with different properties is formed.

Answer: (A)

Verified step by step guidance

1. Understand the difference between physical and chemical changes: A physical change affects the form or state of a substance without altering its chemical composition, while a chemical change results in the formation of one or more new substances with different properties.
2. Identify key indicators of physical changes, such as changes in state (solid, liquid, gas), shape, or size, where the substance remains chemically the same.
3. Recognize indicators of chemical changes, including heat release or absorption, formation of a precipitate, gas production, color change, or creation of a new substance with different properties.
4. Analyze the given observations and determine which one describes a change where the chemical composition remains unchanged, indicating a physical change.
5. Conclude that the observation stating 'The substance changes state, but its chemical composition remains the same' best indicates a physical change.