Which of the following transitions represents a chemical change?

• A. Boiling of ethanol
• B. Burning of magnesium ribbon to form magnesium oxide
• C. Dissolving sugar in water
• D. Melting of ice to form liquid water

Answer: (B)

Verified step by step guidance

1. Understand the difference between physical and chemical changes: A physical change affects the form of a substance but not 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 substance's chemical identity changes:
3. Boiling of ethanol involves changing ethanol from liquid to gas, which is a physical change because the chemical structure of ethanol remains the same.
4. Dissolving sugar in water is a physical change because sugar molecules disperse in water but do not chemically react or change their structure.
5. Melting of ice to form liquid water is a physical change because water changes from solid to liquid without altering its chemical composition.
6. Burning magnesium ribbon to form magnesium oxide is a chemical change because magnesium reacts with oxygen to form a new compound, magnesium oxide, which has different chemical properties from magnesium.