AP Chem is a hard class without a doubt. Most of the people who have taken it have taken regular/honors chem, but there are a few who haven’t. You might have to put in a little bit more time than the others, but it will be worth it in the end. I would get a textbook this summer, just a basic chemistry one and look over the main topics. Watching videos on Khan Academy and Bozeman’s Science on YouTube will help too.
Check out this thread: http://talk.collegeconfidential.com/sciences/1751368-official-ap-chemistry-thread-2015-2016-p4.html Many people have commented who have taken the class. They have some good links on there with stuff to study if you haven’t taken chemistry yet.
As for APUSH, I always found flashcards to help. It’s not about knowing a whole timeline in history, you need to know the ideas and trends like @emilyskates said. In my experience, it was a lot of writing and analyzing essays/documents. To study for tests and quizzes, I always used sites like quizlet to study. I also made outlines every chapter. I only used bullets and I kept the information to no more than 3 sentences per definition. The bigger picture helps a lot.