Which of the following is evidence that a physical change has occurred?

• A. Ice melting into liquid water
• B. Paper burning to produce ash and smoke
• C. Iron rusting to form Fe2O3
• D. Vinegar reacting with baking soda to produce bubbles

Answer: (A)

Verified step by step guidance

1. Understand the difference between physical and chemical changes: A physical change affects the form or appearance of a substance but does not change its chemical composition, while a chemical change results in the formation of one or more new substances with different chemical properties.
2. Analyze each option to determine if the chemical composition changes: For example, ice melting into liquid water involves a change in state (solid to liquid) but the chemical formula H2O remains the same, indicating a physical change.
3. Consider the other options: Paper burning produces ash and smoke, which are new substances formed by chemical reactions; iron rusting forms Fe2O3, a new compound indicating a chemical change; vinegar reacting with baking soda produces bubbles of carbon dioxide gas, showing a chemical reaction.
4. Conclude that the option where the substance changes state without altering its chemical identity is evidence of a physical change.
5. Summarize that melting ice into liquid water is a physical change because it involves a phase change without changing the chemical composition of water.