This OCR GCSE Chemistry (Gateway Science) Higher Tier Paper 4 assesses advanced concepts in environmental chemistry, polymer science, and reaction dynamics. Topics include atom economy, greenhouse gases, Haber process, titration, and stoichiometry. Practical applications such as extraction methods, material properties, and fuel cells are tested. Data interpretation from mass spectrometry, reaction graphs, and polymer structures is emphasized. The paper integrates chemical principles with industrial and environmental considerations, focusing on sustainable practices, process optimization, and scientific reasoning in chemical synthesis and analysis.