My D is also a chem e co-op at Purdue. She considered adding a math minor when she was a freshman but instead took a series of courses to get her certification in collaborative leadership. She was then contemplating adding a concentration but the course selections were too rigid. She loves her co-op company (a polymer company) and has decided to add a bunch of tech electives in material science that aligns with that industry and finance courses because she’s pretty sure an MBA is on the horizon down the road.
My point is that you don’t need to choose anything for right now. You may find that what you think you want may change as you have more experience in your courses and with internships.
Boiler up!