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

• A. Burning of magnesium ribbon
• B. Baking a cake
• C. Rusting of iron
• D. Melting of ice to form liquid water

Answer: (D)

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 properties.
2. Analyze each option to determine if it involves a change in chemical composition or just a change in physical state or appearance.
3. Burning of magnesium ribbon involves a chemical reaction where magnesium reacts with oxygen to form magnesium oxide, so it is a chemical change.
4. Baking a cake involves chemical reactions such as the Maillard reaction and the formation of new compounds, so it is a chemical change.
5. Rusting of iron is a chemical change where iron reacts with oxygen and moisture to form iron oxide (rust), so it is a chemical change.
6. Melting of ice to form liquid water involves a change in physical state from solid to liquid without altering the chemical composition of H2O, so it is a physical change.