Mechanical weathering is the process by which rocks break down into smaller pieces without changing their chemical composition. This occurs through physical forces such as temperature changes, freeze-thaw cycles, and the action of wind or water. For example, when water seeps into cracks in rocks and freezes, it expands, causing the rock to fracture. Another common form of mechanical weathering is abrasion, where rocks are worn down by friction from other rocks or particles. This can happen in rivers, where flowing water carries sediments that grind against the riverbed. Overall, mechanical weathering plays a crucial role in shaping landscapes and soil formation.