This how it works covers How Greenhouse Gases Trap Heat within Greenhouse Effect for GCSE Chemistry. Revise Greenhouse Effect in Atmosphere for GCSE Chemistry with 20 exam-style questions and 12 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 6 of 14 in this topic. Use this how it works to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 6 of 14
Practice
20 questions
Recall
12 flashcards
⚙️ How Greenhouse Gases Trap Heat
Why do CO₂ and CH₄ absorb infrared radiation but N₂ and O₂ do not? The answer lies in molecular structure:
CO₂, CH₄, and H₂O have a molecular structure that allows them to absorb infrared radiation. Once absorbed, the molecule re-emits the energy as infrared radiation in a random direction — about half goes back towards Earth's surface, adding to the warming effect.
Simpler molecules like N₂ and O₂ cannot absorb infrared radiation because of their symmetrical structure. This is why the two most abundant gases in the atmosphere (nitrogen and oxygen) have no role in the greenhouse effect.
The more greenhouse gas molecules there are in the atmosphere, the more infrared radiation is absorbed and re-emitted back towards Earth, and the warmer the surface becomes.