Which of the following is an example of a physical change?

• A. Melting of ice to form liquid water
• B. Burning of methane to produce CO_2 and H_2O
• C. Rusting of iron to form Fe_2O_3
• D. Baking a cake

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 changing its chemical composition, while a chemical change results in the formation of new substances with different chemical properties.
2. Analyze the melting of ice to liquid water: This process changes the state from solid to liquid but the chemical formula H_2O remains the same, indicating a physical change.
3. Examine burning methane (CH_4): This is a combustion reaction producing new substances (CO_2 and H_2O), which is a chemical change.
4. Consider rusting of iron: Iron reacts with oxygen to form iron oxide (Fe_2O_3), a new compound, so this is a chemical change.
5. Look at baking a cake: This involves chemical reactions that produce new substances, so it is a chemical change.