Carbon dioxide and global warming: the greenhouse effect
2 marks · NormalExplain why carbon dioxide is described as a greenhouse gas.
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Because it absorbs infrared radiation emitted by the Earth and re-emits it, warming the atmosphere.
Also accept: CO2 prevents heat escaping from the Earth's surface; CO2 causes the greenhouse effect by trapping heat
Common mistakes: Only stating that CO2 is present in the atmosphere; Not mentioning infrared or heat retention
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Marking points
B1 · 1 mark · Identifies that CO2 absorbs infrared (IR) radiation/heat.
B2 · 1 mark · Adds that this warms the atmosphere or contributes to the greenhouse effect.
Worked solution
Carbon dioxide is called a greenhouse gas because it absorbs infrared radiation emitted by the Earth's surface and re-emits it, warming the Earth's atmosphere.