An example of physical weathering process is

Step 1: Analyze the question The question asks which option is a physical (mechanical) weathering process. Physical weathering breaks rock into smaller pieces without changing its chemical composition.

Step 2: Explain the concept Weathering is the breakdown of rocks in place. There are two main types:

• Physical (mechanical) weathering: Rocks are broken apart by temperature changes, frost action, pressure release, or salt crystal growth. Examples include exfoliation, frost shattering (freeze-thaw), and granular disintegration.
• Chemical weathering: The minerals in the rock are chemically altered. Examples include carbonation, hydration, hydrolysis, oxidation, and solution.

Step 3: Check each option

• A. Carbonation: Carbon dioxide dissolved in rainwater forms a weak carbonic acid, which reacts with limestone and chalk. This is chemical.
• B. Exfoliation: Rocks, especially in hot deserts and tropical areas like northern Nigeria, heat up by day and cool at night. The outer layers expand and contract repeatedly, so they peel off in sheets like onion skin. No chemical change occurs. This is physical.
• C. Hydration: Minerals absorb water, swell, and change chemically (for example, anhydrite becomes gypsum). This is chemical.
• D. Hydrolysis: Water reacts chemically with minerals such as feldspar, turning them into clay. This is chemical.

Step 4: Answer Only exfoliation is physical weathering, so the answer is B.

Tip: Many chemical weathering processes end in "-tion" or "-sis" and involve water or acids reacting with minerals (carbonation, hydration, hydrolysis, oxidation). Remember that exfoliation = peeling like an onion, which is a physical process caused by temperature change. Note that hydration looks like it might be physical because it involves swelling, but it is classed as chemical because the minerals change.