What describes chemical weathering?

• A. The physical breakdown of rocks into smaller pieces.
• B. The removal of rocks by erosion.
• C. The process that alters the chemical structure of minerals in rocks, often through reactions with water and atmospheric gases.
• D. The deposition of minerals.

Answer: (C)

Chemical weathering is the process that changes the minerals in rocks through chemical reactions, often involving water and gases in the atmosphere. When minerals react, their structure and composition can transform into new substances—like feldspar turning into clay minerals, calcite dissolving in acidic rain, or iron-bearing minerals forming oxides. This is different from mechanical weathering, which breaks rocks into smaller pieces without changing their chemical makeup. Erosion and deposition describe the movement and settling of weathered material, not the chemical alteration itself. So the description that emphasizes chemical alteration of minerals via reactions with water and atmospheric gases best captures chemical weathering.