Which of the following pairs are examples of chemical changes that produce an odor?

• A. Evaporating alcohol and freezing water
• B. Boiling water and crushing garlic
• C. Burning sugar and rotting eggs
• D. Dissolving salt in water and melting ice

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the difference between physical and chemical changes. A physical change alters the form or state of a substance without changing its chemical identity, while a chemical change results in the formation of new substances with different properties.
2. Step 2: Identify which processes in the options involve chemical changes. Evaporating, freezing, boiling, crushing, dissolving, and melting are physical changes because they do not produce new substances.
3. Step 3: Recognize that burning sugar is a chemical change because it involves combustion, producing new substances and often releasing odors.
4. Step 4: Recognize that rotting eggs is a chemical change due to decomposition, which produces new compounds that emit characteristic odors.
5. Step 5: Conclude that only the pair 'burning sugar and rotting eggs' represents chemical changes that produce an odor, as the other pairs involve physical changes without new substances or odors formed.