Which of the following examples is evidence of a physical change?

• A. Silver tarnishing when exposed to air
• B. Ice melting to form liquid water
• C. Burning of methane (CH_4) in oxygen
• D. Iron rusting to form Fe_2O_3

Answer: (B)

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 new substances with different chemical properties.
2. Analyze each example to determine if the chemical composition changes: For silver tarnishing, silver reacts with sulfur compounds in the air forming silver sulfide, which is a chemical change.
3. For ice melting to form liquid water, the substance (H_2O) changes state from solid to liquid, but its chemical composition remains the same, indicating a physical change.
4. Burning methane (CH_4) in oxygen involves a combustion reaction producing new substances like CO_2 and H_2O, so this is a chemical change.
5. Iron rusting to form Fe_2O_3 involves iron reacting with oxygen to form a new compound (iron oxide), which is a chemical change.