Chemistry in Year 12 is similar to content in GCSEs, it just goes into a bit more detail. It's hard at first but when you revise it gets a lot easier. Chemistry in Year 13 is a lot harder though, it is a big step up from AS but as you practise past papers and understand the content it becomes a lot easier. I have my A-Levels soon and I'm still trying to wrap my head around the A2 stuff lol