Which of the following is an example of chemical weathering?

• A. The breaking of rocks by freezing and thawing
• B. The cracking of rocks due to plant roots
• C. The rusting of iron rocks
• D. The abrasion of rocks by wind-blown sand

Answer: (C)

Verified step by step guidance

1. Understand the difference between physical (mechanical) weathering and chemical weathering. Physical weathering involves the breaking down of rocks into smaller pieces without changing their chemical composition, while chemical weathering involves chemical changes that alter the minerals within the rock.
2. Analyze each option to determine if it involves a chemical change or just a physical change:
3. The breaking of rocks by freezing and thawing is physical weathering because water expands when it freezes, causing the rock to crack without changing its chemical makeup.
4. The cracking of rocks due to plant roots is also physical weathering, as roots physically grow and exert pressure on rocks, causing them to break apart.
5. The rusting of iron rocks is chemical weathering because it involves a chemical reaction (oxidation) where iron reacts with oxygen and water to form rust, changing the chemical composition of the rock.