Which process changes rocks primarily through chemical reactions like oxidation or hydrolysis?

• A. Chemical weathering
• B. Physical weathering
• C. Erosion
• D. Deposition

Answer: (A)

Chemical weathering is the process that primarily changes rocks through chemical reactions. Minerals in rocks react with water, oxygen, or weak acids, leading to dissolution, the formation of new minerals, or changes in mineral structure. Oxidation adds oxygen to minerals like iron, turning some rocks rusty; hydrolysis involves water reacting with minerals (such as feldspars turning into clay minerals). These chemical changes alter composition and texture, not just the rock’s size. By contrast, physical weathering breaks rocks into smaller pieces without changing their minerals, erosion moves those pieces, and deposition is the settling of sediments. So, when the description highlights chemical reactions like oxidation or hydrolysis, chemical weathering is the process at work.