AQA · A-Level · Chemistry
Course version: 7405 · Version from Sept 2016
Ozone, formed naturally in the upper atmosphere, is beneficial because it…
Full specification wording
Ozone depletion: Ozone, formed naturally in the upper atmosphere, is beneficial because it absorbs ultraviolet radiation.
Ozone, O₃, forms naturally high in the atmosphere: ultraviolet light splits O₂ into oxygen atoms, and each atom joins another O₂ molecule to give O₃.
Checked against the AQA 7405 specification (opens in a new tab) on .
- Point 1 of 6
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Ozone, O₃, forms naturally high in the atmosphere: ultraviolet light splits O₂ into oxygen atoms, and each atom joins another O₂ molecule to give O₃. The useful part is what happens next. Ozone absorbs ultraviolet radiation, the energy breaking it back to O₂ and an oxygen atom, which then reforms ozone. The cycle absorbs high-energy ultraviolet continuously without consuming the ozone, which is why a thin layer of gas can shield the whole surface. The radiation it removes is the band that damages DNA, so a thinner layer means more skin cancer, more cataracts and damage to crops and plankton. Note the type of radiation carefully: ozone in the stratosphere is filtering ultraviolet, not infrared, so it is not acting against global warming.
What earns the marks
- Stating that ozone absorbs ultraviolet radiation.
- Placing this ozone in the upper atmosphere or stratosphere.
- An equation showing ozone forming or absorbing ultraviolet, such as O• + O₂ → O₃.
- A named consequence of more ultraviolet reaching the surface, such as skin cancer or cataracts.
Common mistakes and how to put them right
Saying ozone prevents global warming, an answer AQA offers as a wrong option in multiple choice.
Saying ozone absorbs infrared radiation, which is what greenhouse gases do.
Writing that ozone "absorbs radiation" without naming ultraviolet.
Confusing low-level ozone, which is a pollutant, with stratospheric ozone, which is beneficial.
Exam tips
- Use the word ultraviolet in every answer about the ozone layer; a general word for radiation will not score.
- Keep ozone depletion and the greenhouse effect in separate mental boxes; examiners set them as distractors for each other.
- State where the ozone is, since the same molecule is harmful at ground level.
Try the lesson
The start of the Ozone depletion: Ozone, formed naturally in the upper atmosphere, is beneficial because it absorbs ultraviolet radiation. lesson, made from checked teaching notes for this specification point.
Have a go first
Ozone in the upper atmosphere is beneficial to life on Earth. Which type of radiation does it absorb?
Listen
Ozone, O₃, forms naturally high in the atmosphere: ultraviolet light splits O₂ into oxygen atoms, and each atom joins another O₂ molecule to give O₃. The useful part is what happens next. Ozone absorbs ultraviolet radiation, the energy breaking it back to O₂ and an oxygen atom, which then reforms ozone. The cycle absorbs high-energy ultraviolet continuously without consuming the ozone, which is why a thin layer of gas can shield the whole surface. The radiation it removes is the band that damages DNA, so a thinner layer means more skin cancer, more cataracts and damage to crops and plankton. Note the type of radiation carefully: ozone in the stratosphere is filtering ultraviolet, not infrared, so it is not acting against global warming. A strong answer earns marks for these points. stating that ozone absorbs ultraviolet radiation. placing this ozone in the upper atmosphere or stratosphere. an equation showing ozone forming or absorbing ultraviolet, such as O• + O₂ → O₃. a named consequence of more ultraviolet reaching the surface, such as skin cancer or cataracts. Exam tip: Use the word ultraviolet in every answer about the ozone layer; a general word for radiation will not score.
Key words
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stratospheric ozone
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ultraviolet absorption
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protection from harmful radiation
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not the greenhouse effect
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See every definition
- stratospheric ozone
- Ozone formed naturally in the upper atmosphere, which is beneficial because it absorbs ultraviolet radiation.
- ultraviolet absorption
- Ozone absorbs ultraviolet radiation, the energy breaking it back to O₂ and an oxygen atom, which then reforms ozone.
- protection from harmful radiation
- The radiation removed is the band that damages DNA, so a thinner layer means more skin cancer, more cataracts and damage to crops and plankton.
- not the greenhouse effect
- Ozone in the stratosphere is filtering ultraviolet, not infrared, so it is not acting against global warming.
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