Sorry I'm replying quite late guys
Maths advice here, yeah, for C1, literally revise and practice as much GCSE maths as you can, as C1 is basically GCSE with a bit extra such as calculus. Maths is not a very hard subject if you get it, but if not, you need to make sure you either go to you're teacher or read over everything. There's literally not much more to maths, and it feels bad saying that because it may seem a little insulting, but year, practice is key with maths.
Since you're all AQA chemists, I'll start there. I found chemistry to be the easiest subject for me personally, buy my ISA screwed me up (got a D in it) and ended up with a very low A overall. Chemistry isn't too hard a subject if you do the work you need too. I struggled at the beginning of AS, because I did OCR chemistry GCSE, and the content is very different from the get go. I found the best way for me to overcome this was to constantly bug my chemistry teachers to make sure I fully understood it. Chapter 3 (bonding) will be a topic where I would expect everyone of you (no offence) to struggle to get your head around - I know I did, but you have to make sure you go through if carefully and understand the concept. If it ever comes, and you feel like you just don't get it, just PM me and I'll be glad to help with it because I know how frustrating it gets. You'll find once you understand chemistry concepts, it gets a LOT easier, them the next challenge is applying them- that's not too hard as long as you've understood the concepts properly. AQA examiners are very very fussy so include in the exam all relevant info you think could award you points.
On the point of the ISA (3T), you carry out an experiment (either a unit 1 practical such as inorganic titration or a unit 2 practical such as concentration effect on rate) and then you have a written test where section A would focus on the experiment -(results, experimental issues etc), then section B is just a general investigative skill assessment, so you could be given a data, graphs etc, and asked why you'd expect to see x, or what you expect to observe as x is added etc. AQA GCSE chemists are probably at an advantage here.
If you have any other questions, fire away, and oh yeah, chemguide - REMEMBER IT, it is literally one of the best resource available for chemistry. Good luck guys
hopefully you'll love chemistry as much as I did
For techno, 3X is an EMPA, you are less likely to do this compared to the ISA, hence why ISA grade boundaries are so much higher
You guys won't need to do much preparation over the summer for chemistry since the topics are quite different, but practice using moles since it is quite integral to chemistry - understand the concept of moles, and how you can get from it to mass, or to concentration etc