[gradstudent]

I'm a grad student in environmental chemistry. I'm taking a course in environmental geochemistry course (emphasis in aquatic chemistry). I did not take a physical chemistry course as an under grad and this new course seems to be heavily built on that. We have been discussing the activities of chemicals and how they relate to chemical concentrations. I understand that the concentration is multiplied by a coefficient to determine the activity but what exactly is a chemical's activity? Does chemical activity always increase with increased concentration? Second topic/question - what is chemical potential? How does chemical activity relate to the chemical potential? I'd really appreciate any clarification on these topics. Thanks!