Which type of weathering would most likely reduce a rock's mass without changing its chemical composition?

• A. Physical (Mechanical) Weathering
• B. Chemical Weathering
• C. Biological Weathering
• D. Solution Weathering

Answer: (A)

Mechanical weathering reduces mass by physically breaking rock into smaller pieces or peeling away outer layers, while the minerals themselves aren’t chemically altered. Freeze-thaw cycles, abrasion, and exfoliation are classic ways this happens. Since no chemical reactions occur to change the minerals, the rock’s chemical composition stays the same even as its mass decreases.

Chemical weathering changes the minerals themselves, forming new substances or dissolved ions, so the composition is altered. Biological weathering can involve mechanical breakup plus chemical effects from organisms, which can also change composition. Solution weathering dissolves minerals in water, clearly changing composition.