Mechanical weathering is the process of breaking big rocks into little ones. This process usually happens near the surface of the planet. Temperature also affects the land. The cool nights and hot days always cause things to expand and contract. That movement can cause rocks to crack and break apart.
Chemical weathering occurs when chemical reactions weaken and decompose rocks, often acting alongside the physical breakdown of rock, aka mechanical weathering. This process involves a chemical change, which actually alters the rock's or mineral's chemical composition.