I have taught science for 12 years and find that gestures are perfect for reinforcing the concepts. For weathering, we use a chopping gesture as if you were giving a massage. For erosion, we use a pinching gesture and then follow that by putting pinched fingers over head. This leads to deposition when we place the pinched fingered on the other side of our body and then release. We engage in a teach-okay with the two types of weathering. For chemical, we take a deep breathe for oxidation, a water wave gesture for hydrolysis, and a gesture like we are drinking a soda for carbonation. For mechanical weathering, we represent freeze-thaw by shivering and then relaxing all of our muscles. We also represent salt wedging by using a salt shaker gesture and then wedge one hand into the other. Hope this helps! Have fun with it and even let the kids come up with them!