I do chem; tips for the holidays = rest; but if you really want to study = do a bit of revision on maybe Mod 4 (enthalpy, gibbs free) cause that can reappear in HSC, aside from that make sure your mod 2 calculations are all good (you're fine with moles and stuff)
During yr 12 tips = do some quick notes (emphasise on quick rather than aesthetically pleasing) as you learn content in order to fully understand it all (structure it based on syllabus); if you don't understand a concept dont bury it, ask someone; and also don't worry if you realise you can't fully remember everything as chem is a content heavy subject (when exams arrive, just do past papers and targeted quick notes on stuff you completely can't remember, and the content will all come back to you)
Other than that dont worry, it's just yr 11 but new content