Exam Focus

Very High Frequency

What Examiners Ask About the Greenhouse Effect

• "Explain the greenhouse effect" — must include: short-wave radiation in, surface warms, long-wave IR emitted, absorbed by greenhouse gases, re-emitted back to Earth (4–5 marks)
• "Name three greenhouse gases" — CO₂, CH₄, H₂O vapour (1 mark each)
• "Explain the enhanced greenhouse effect" — human activities increase greenhouse gas concentrations, more IR trapped, extra warming (3 marks)
• "Give two sources of methane" — cattle, rice paddies, landfill (2 marks)
• "Why is the natural greenhouse effect important?" — without it Earth would be -18°C, too cold for most life (1–2 marks)

Mark Scheme Language

• Use the words "absorb" and "re-emit" — not just "trap"
• Specify "infrared" radiation — not just "heat" or "radiation"
• Mention "long-wave" or "low energy" for the IR emitted by Earth

Edexcel 1CH0: Examined in Paper 2 (1CH0/2). The mechanism of the greenhouse effect and the role of specific greenhouse gases (CO₂, methane, water vapour) are tested in Edexcel Paper 2. In Edexcel-style questions, the command word "Suggest" appears frequently — use your chemistry knowledge to apply to an unfamiliar context.