OCR Gateway GCSE Additional Science Essentials covers all the exam-assessed content on the OCR Gateway Additional Science specification. It is designed to help students get the most out of their revision – information is broken down into manageable chunks and higher tier material is clearly differentiated on the page.OCR Gateway GCSE Additional Science Essentials covers all the exam-assessed content on the OCR Gateway Additional Science specification. It is designed to help students get the most out of their revision – information is broken down into manageable chunks and higher tier material is clearly differentiated on the page.