I think the requirements are put in place to make sure your a level journey runs smoothly and you don’t find it too difficult. I do chemistry myself and there’s insane amounts of calculations I’d say for you to have a grade 7 minimum to make your life easier, I think if you’re really determined to do chem then you’ve got to put incredible amounts of effort, I’d advice you to work harder on maths rn because honestly chem is really difficult even for the brightest students. Best of luck!