Which statement describes mechanical (physical) weathering?

• A. The chemical breakdown of rocks into smaller pieces without changing their chemical composition.
• B. The physical breakdown of rocks into smaller pieces without changing their chemical composition.
• C. The chemical alteration of minerals by reactions with water.
• D. The deposition of sediments.

Answer: (B)

Mechanical weathering is the physical breakup of rocks into smaller pieces without changing their chemical makeup. The statement describes rocks being divided into smaller fragments while their minerals stay chemically the same, which is exactly what mechanical weathering does. Think of processes like frost wedging, where water seeps into cracks and expands when it freezes, or thermal expansion, where repeated heating and cooling causes cracks to grow. Abrasion from wind or water and roots growing into cracks also break rocks apart without altering their chemistry. In contrast, chemical weathering changes the minerals themselves through reactions with water or other chemicals, and deposition is simply sediments settling out, not breaking down rock.