Combined Science (A) J250,10 Higher November 2020, OCR GCSE Past Papers with Mark Schemes

1. Chemical Reactions and Catalysts – Role of enzymes in biological reactions, catalysts in decomposition reactions, and factors affecting reaction rates.

2. Periodic Table and Element Properties – Trends in Group 0 boiling points, Group 1 reactivity with water, and metallic bonding in sodium.

3. Fractional Distillation and Hydrocarbon Processing – Separation of crude oil, cracking of long-chain hydrocarbons, and differences in boiling points between alkanes.

4. Reaction Rates and Equilibrium – Effect of concentration and temperature on reaction rates, dynamic equilibrium in ammonia production, and predicting equilibrium shifts.

5. Environmental Chemistry and Atmospheric Changes – Evolution of Earth’s atmosphere, greenhouse effect, nitrogen oxides in vehicle emissions, and catalytic converters.

6. Redox Reactions and Halogens – Displacement reactions between halogens, oxidation and reduction in ionic half-equations, and reactivity trends in Group 7 elements.