BRAINCAKEInfrared Radiation and the Greenhouse Effect
The Earth absorbs radiation from the Sun, mainly visible and ultraviolet, and warms up. The warm surface then re-emits energy as infrared radiation.
Some gases in the atmosphere, called greenhouse gases, contain bonds that absorb this infrared radiation. The main ones are carbon dioxide (C=O bonds), methane (C-H bonds) and water vapour (O-H bonds). This is the same process used in IR spectroscopy: the bonds absorb IR radiation at frequencies that match their vibrations.
The absorbed energy makes the bonds vibrate more. The molecules then re-emit infrared radiation in all directions, including back towards the Earth's surface. This keeps the lower atmosphere warmer than it would otherwise be. This is the greenhouse effect; without it the Earth would be too cold for most life.
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More in Organic Analysis
- Identifying Functional Groups
- Test Tube Tests for Organic Compounds
- High Resolution Mass Spectrometry
- Precise Relative Molecular Mass
- Infrared Spectroscopy
- Bond Vibrations and IR Absorption
- The Fingerprint Region
- Interpreting IR Spectra
All 9 lessons in Organic Analysis · All AQA AS-level Chemistry topics