There's no such thing as "mechemical weathering." You're likely thinking of mechanical weathering, which is the physical breakdown of rocks into smaller pieces. Here are some agents of mechanical weathering:

* Frost Wedging: Water seeps into cracks in rocks, freezes, expands, and puts pressure on the rock, eventually breaking it apart.

* Root Wedging: Plant roots grow into cracks in rocks, expanding and putting pressure on the rock, which can cause it to break.

* Abrasion: Rocks are rubbed together by wind, water, or ice, which grinds them down. This can also happen when rocks are carried by glaciers or rivers.

* Exfoliation: Pressure release from the removal of overlying rock layers causes the outer layers of a rock to peel off like an onion.

* Thermal Expansion and Contraction: Repeated heating and cooling of rocks can cause them to expand and contract, which can eventually lead to cracks and fractures.

Chemical weathering, on the other hand, involves the breakdown of rocks through chemical reactions.