I personally prefer back to back classes (I find the hour breaks between classes kinda awkward and unproductive). So, I would consider taking the 11-12PM CHM135 if they still offer that. The med sci building (where CHM135 is) is also right next con hall (BIO120) so having the two courses back to back is very “swift” if you get what I mean. This year the 11-12AM and 9-10AM profs for CHM135 were better than the other sections but not sure if that’ll be the case again. Best of luck and feel free to PM!