Which of the following pairs shows one example of a physical change and one example of a chemical change?

• A. Cooking an egg and evaporating alcohol
• B. Rusting iron and dissolving sugar in water
• C. Boiling water and freezing water
• D. Melting ice and burning wood

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the difference between physical and chemical changes. A physical change affects the form of a substance but not its chemical composition, such as changes in state (melting, boiling, freezing). A chemical change results in the formation of one or more new substances with different properties, such as burning or rusting.
2. Step 2: Analyze each pair to identify which example is a physical change and which is a chemical change. For example, 'melting ice' is a physical change because ice changes from solid to liquid water without altering its chemical structure.
3. Step 3: Identify the chemical change in the pair. 'Burning wood' is a chemical change because it involves combustion, producing new substances like carbon dioxide, ash, and water vapor.
4. Step 4: Confirm that the pair contains one physical change and one chemical change. 'Melting ice' (physical) and 'burning wood' (chemical) satisfy this condition.
5. Step 5: Review the other pairs to see why they do not fit. For example, 'cooking an egg' is chemical, but 'evaporating alcohol' is physical; 'rusting iron' is chemical, but 'dissolving sugar in water' is physical; 'boiling water' and 'freezing water' are both physical changes.