go on Quizlet and just memorise ready-made flashcards...that's if you haven't made flashcards...or actually even better if you have mygcsescience (my school gave that) do the videos and quizzes and exam Qs for the topic - about 8-10 videos per topic and then work on the parts you get wrong...Good luck you can do it if you try.. make rough notes for the videos..just reminders and go over them frequently e.g. on the way to school