Chemistry - Ozone (C6)

These cards are for GCSE chemistry higher and are about the depeletion of the ozone layer and CFC's the main cause.

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What is the Ozone?

General Facts

  • The ozone layer is in the stratospher. There are only tiny amounts of Ozone in this layer hwver these bits still absorb most of the harmful Uv light from the sun.
  • The more depleted the Ozone gets the more harmful UV light can get through which increases the risk of cancer and other diseases.
  •  When CFCs were first discovered they were thought to be totally safe however we now know that they attack the ozone with free radicals and are very hard/ expensive to get rid off.

Ozone Layer - This is a layer in the atmosphere which absorbs harmful ultraviolet light this layer protects the humans from diseases such as Skin Cancer which can be caused by to much exposer to UV light.

CFCs - CFCs are organic compounds that contain carbon, chlorine and fluorine. These compounds were mainly used in refrigerators but have now been banned because they contribute to the depletion of the ozone layer. Uv light in the stratosphere is strong enough to break the bonds 

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How the Ozone works

Need to Know Facts

  • Visible light can penetrate the Ozone layer easily without causing it harm however UV light is absorbed which stops it from reaching earth. 
  • The UV part of the electro-magnetic spectrum has exactly the right frequency to make the ozone vibrate, this energy is converted into movement cells inside each molecule and so the thicker the Ozone the greater amount of UV light is absorbed.
  • CFC is short for Chlorofluorocarbon
  • CFC's do not stay above where they are released but travel to the poles because that is where convection current takes them with everything moving upwards towards the poles.
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CFC's and Free Radicals

In the stratosphere

  • In the stratosphere the UV light is strong enough to break single chlorine atoms from the CFC molecule,  this single chlorine atom is called a chlorine free radical.
  • A covalent bond is made of 2 electrons , when the bond breaks the bond can split into two equal halves to make free radicals, and these chlorine free radicals are very reactive.
  • A chain reaction is then set off producing another chlorine free radical which reacts further.
  • Chlorine Free radicals react with the Ozone molecule O3  creating again more free radicals and turning the O3 into O2 which does not protect the earth from harmful UV as it does not absorb it. .

These Chlorine Free radicals could continue doing this forever however after some time say 30 years they escape into space which stops then from destroying the ozone O3. 

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