What is an example of chemical weathering, as opposed to mechanical weathering?

I’m stuck on this question cuz i’m stupid sksksksk

In an experiment examining the effects tai chi on arthritis pain, callahan (2010) selected a large sample of individuals with doctor-diagnosed arthritis. half of the participants immediately began a tai chi course and the other half (the control group) waited 8 weeks before beginning. at the end of 8 weeks, the individuals who had experienced tai chi had less arthritis pain that those who had not participated in the course.

1. fold your hands together so your thumbs cross over ,and look at your thumbs. which thumb feels most "comfortable" on top is actually controlled by a gene. the left thumb folding over the right thumb is a domi