Ozone Depleting Substances — Prelims Strategy

Prelims Strategy

Build a three-column comparison of CFCs, HCFCs and HFCs using composition, ozone effect and climate concern. Do not assume that a lower ozone-depletion potential means zero, or that zero ozone-depletion potential means zero warming influence. Match each treaty instrument to its role.

For mechanism questions, follow persistence, stratospheric transport, ultraviolet breakdown and reactive chemistry. Reject explanations based solely on gases being too heavy to rise or on a literal hole in the atmosphere. For polar questions, connect cold conditions, cloud-surface chemistry and returning sunlight rather than selecting one isolated factor.

In policy questions, distinguish new production controls from management of existing equipment. A training initiative is evidence of capacity-building, not direct proof that every unit has stopped leaking. Keep event dates separate from treaty adoption and entry-into-force dates. During review, explain each mistaken substitution—ozone versus climate, phaseout versus phasedown, or implementation activity versus atmospheric outcome—rather than memorising the correct option alone.