Differentiate physical and chemical weathering and give an example of each process affecting rocks at Earth's surface.

• A. Physical weathering fragments rocks without chemistry (frost wedging); chemical weathering alters minerals (oxidation, hydrolysis)
• B. Physical weathering changes mineral composition; chemical weathering fragments rocks
• C. Both only occur beneath oceans
• D. Chemical weathering only occurs at night

Answer: (A)

The main idea being tested is how rocks break down in place by two different kinds of processes: physical weathering and chemical weathering. Physical weathering breaks rocks into smaller pieces without changing the minerals that make up the rock. Frost wedging is a classic example: water seeps into cracks, freezes, expands, and pries the rock apart, producing smaller fragments while the mineral makeup stays the same. Chemical weathering, on the other hand, alters the minerals themselves through reactions with water and air, forming new minerals or dissolving parts of the rock. Oxidation of iron minerals gives a buildup of rust and weakens rocks, while hydrolysis can transform feldspar into clay minerals, changing the rock’s composition.

These ideas fit the way rocks at Earth’s surface actually weather: physical processes physically break apart material; chemical processes chemically transform the minerals present. The other statements don’t fit: physical weathering does not change mineral composition, chemical weathering isn’t limited to nighttime, and these processes don’t require oceans to occur—they operate on land wherever weathering agents like water, air, and temperature changes are present.