Summer Internship & Classes together, how difficult?

<p>I am planning to take 8 units in summer 1, 2014. One is Chem 7L, which I heard it is a lot of work, the other one hasn't been decided yet, but if possible, I want to do Chem 140A (rumors said it's hard too). How difficult it is to take CHEM 7L and 140A in the summer while doing an internship? Anyone has similar experience? Thank you very much for sharing with me. </p>