The difference between mechanical weathering and chemical weathering lies in the processes that break down rocks. Mechanical weathering involves physical forces causing rocks to fracture or break apart without changing their chemical composition. Examples include freeze-thaw cycles or abrasion from wind and water. In contrast, chemical weathering involves chemical reactions that alter the minerals within rocks, often due to exposure to water and atmospheric gases, leading to changes in composition. Both processes are essential for soil formation and landscape evolution.