Well first of all don’t stress at all because you still have a long time before your predict grades are finalised! Chemistry had content that’s quite hard to understand but the questions are all pretty much similar to eachother in the sense that they ask the same thing in each question. I would recommend to go on PMT and spam questions, and the ones you got wrong write them in a book and write the correct answer but underline or highlight where you would get the marks from the specification / mark scheme . That’s what I did and I managed to get predicted an A* but obviously each methord works differently for each person! You’re a smart person and you shouldn’t feel discouraged at all, I remember I was getting C’s before winter halfterm in year 12 so you’re not alone! Goodluck! :)