Which type of weathering involves chemical changes such as those caused by acid rain?

• A. Physical weathering
• B. Biological weathering
• C. Chemical weathering
• D. Weathering by ice

Answer: (C)

Chemical weathering happens when minerals in rock undergo chemical changes due to reactions with substances in the environment. Acid rain brings acids that react with minerals like calcite in limestone, dissolving minerals and forming new compounds rather than just breaking the rock apart. This alters the rock’s composition over time. Physical weathering, on the other hand, breaks rock into smaller pieces without changing the minerals themselves—for example, by freeze-thaw cycles or abrasion. Biological weathering can involve organisms contributing to breakdown, but the key idea is that chemical alterations to the minerals are taking place. Ice-related weathering is a mechanical process where water freezes in cracks and pushes the rock apart.