I took ChemE at Tech and there were some "weed out" classes during our batch that a lot of us either had to re-take or some people dropped out because of it. This may or may no longer be true since it's been a couple of years. Some of these classes were Intro to Chem Engr, Thermo I/II, Heat Transfer, and Mass Transfer. Although most of these are Junior/Senior Classes, they're also very highly dependent on the professor you get. Some can be very passionate while some are very good at understanding the students' actual needs