I personally found chemistry my easiest subject (out of bio, chem, physics and maths) at AS (got an A), especially the first exam, since it was all very similar to GCSE. Don't know why I found chemistry so easy at AS (bit harder at A2 haha). It's definitely the subject I put the least amount of work into (and i'm a very hard worker haha, spend loads of times on biology just cause there is so much to learn and lots of time practicing maths as it needs lots of practice)