Which statement correctly differentiates physical weathering from chemical weathering?

• A. Both processes always involve chemical reactions; physical weathering involves only heat.
• B. Physical weathering breaks rocks into smaller pieces without changing their chemical composition, while chemical weathering alters the minerals in rocks through chemical reactions.
• C. Physical weathering changes chemical composition; chemical weathering breaks rocks into pieces.
• D. Physical weathering forms new minerals; chemical weathering only breaks rocks.

Answer: (B)

Physical weathering is about breaking rocks into smaller pieces without changing what the minerals are made of, while chemical weathering changes the minerals themselves through chemical reactions. For example, frost action or root growth can physically crack and crumble rock, and even when water is present, the minerals remain the same substances. Chemical weathering, on the other hand, involves reactions that dissolve or transform minerals—feldspar turning into clay minerals, calcite dissolving in acidic water, or iron minerals oxidizing to form rust-like compounds. This is why the correct statement pairs physical weathering with fragmentation without chemical change, and chemical weathering with alteration of minerals via chemical reactions. The other ideas misstate what happens: physical weathering does not require chemical reactions and does not create new minerals, and chemical weathering does not simply break rocks into pieces.