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IGCSE · Practice questions · Greenhouse gases and climate change

Absorb, re-emit, warm.

Six original Cambridge-style questions on greenhouse gases, photosynthesis and climate change.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.
Keep these straight

Gases, effect, sink, strategy.

01
Recall
[2 marks]

Name two greenhouse gases and give one source of each.

  • Carbon dioxide: complete combustion of carbon-containing fuels. ✓
  • Methane: decomposing vegetation or waste gases from digestion in animals. ✓
02
Explain
[3 marks]

(Extended) Explain how an increase in greenhouse gases causes global warming.

  • The Earth's surface absorbs energy from the Sun and emits thermal energy as infrared radiation. ✓
  • Greenhouse gases absorb this infrared and re-emit it, some back towards the Earth. ✓
  • So less thermal energy is lost to space and the average temperature rises. ✓
03
Recall
[2 marks]

Write the word equation for photosynthesis and state the two conditions it needs.

  • carbon dioxide + water → glucose + oxygen ✓
  • Light energy and chlorophyll. ✓
04
Calculation
[3 marks]

(Extended) Calculate the mass of glucose made when 66 g of carbon dioxide is absorbed by photosynthesis. (Mr: CO2 = 44, C6H12O6 = 180)

  • Moles of CO2 = 66 ÷ 44 = 1.50 mol ✓
  • Moles of glucose = 1.50 ÷ 6 = 0.250 mol ✓
  • Mass of glucose = 0.250 × 180 = 45.0 g ✓
05
Explain
[4 marks]

Describe four strategies to reduce the effects of climate change and explain how each helps.

  • Planting trees: more photosynthesis removes carbon dioxide. ✓
  • Reducing livestock farming: less methane released. ✓
  • Decreasing the use of fossil fuels: less carbon dioxide released. ✓
  • Using hydrogen and renewable energy such as wind or solar: energy without carbon dioxide emissions. ✓
06
Analysis
[2 marks]

Suggest two consequences of climate change.

  • Rising sea levels from melting ice, causing flooding. ✓
  • More extreme weather (droughts, storms) and changes to where crops can be grown. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.