Cambridge IGCSE Chemistry · Syllabus 0620 · Chemistry of the Environment
Global Warming
What is Global Warming?
The rise in the average temperature of the Earth's surface caused by higher levels of greenhouse gases in the atmosphere. Carbon dioxide and methane are the two gases named in this topic. Global warming in turn leads to climate change, which is the long-term change in weather patterns across the world. The syllabus asks for the sequence: higher levels of the gas, increased global warming, then climate change.
This definition is part of the Chemistry of the Environment chapter in Cambridge IGCSE Chemistry.
Common mistakes with Global Warming
- “Clean air contains no carbon dioxide.” Defect Treats a normal component as a contaminant. Chemistry Carbon dioxide is part of the remainder of clean dry air. The adverse effect belongs to higher levels of it. Repair “The remainder is mainly noble gases and carbon dioxide.” Transfer What is the required wording for its effect? “Higher levels increase global warming and climate change.”
- “Carbon dioxide causes acid rain.” Defect The effect belongs to a different pollutant. Chemistry Acid rain is caused by sulfur dioxide and oxides of nitrogen. The named effect of carbon dioxide is increased global warming and climate change. Repair Learn the pairs in blocks: climate for \(\mathrm{CO_2}\) and \(\mathrm{CH_4}\); acid rain for \(\mathrm{SO_2}\) and NOx. Transfer A limestone statue is eroding. Which two pollutants? Sulfur dioxide and oxides of nitrogen.
- “Sulfur dioxide is the main cause of global warming.” Defect The mirror image of the previous error. Chemistry Sulfur dioxide causes acid rain. The greenhouse gases named in this topic are carbon dioxide and methane. Repair Two gases for climate, two for acid rain — and none in both. Transfer Which control targets sulfur dioxide? Low-sulfur fuels, or flue gas desulfurisation with calcium oxide.
- Supplement 10.3.8 “A catalytic converter turns harmful gases into harmless ones.” Defect One word too strong. Chemistry Nitrogen is benign, but carbon dioxide contributes to global warming. The syllabus wording is less harmful products. Repair Write “less harmful” and, if there is room, name the residual concern. Transfer Does fitting a converter reduce carbon dioxide from a car? No — it increases it slightly, by oxidising carbon monoxide.