Flashcards for OCR GCSE Chemistry Controlling reactions, covering the key terms, definitions and equations you need to recall for Paper 1 and Paper 2 (Foundation Tier) or Paper 3 and Paper 4 (Higher Tier). 24 cards, matched to the OCR GCSE Chemistry (J248) specification. Recall questions account for roughly 40% of marks at GCSE Chemistry, so these target the marks you can secure before the paper starts.