C6e Ozone Layer


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C6e Ozone Layer

  1. 1. C6e Depletion of the Ozone Layer • A chlorofluorocarbon (CFC) is an organic molecule containing ___________, _____________ and ___________ atoms. • They are used as_____________________________________________ • They are banned from being used in the UK because they have lead to the ____________________ (thinning) of the ozone layer. Higher Describe how scientists’ attitude to CFCs has changed In the beginning scientists thought CFC’s were great because: • CFC’s are 1. 2. 3. 4. 5. • These properties make them ideal for Later they discovered: • CFC’s deplete the ozone layer (make it thinner) • so they banned them from use. Continuing Problems 1. 2. So what have countries done to try and stop the depletion of the ozone layer? • •
  2. 2. • What is ozone, O3? • Ozone is a form of oxygen with the formula ______ . • When UV light shines on CFC’s ______________ atoms are formed Why do we need ozone? Increased levels of ultraviolet light can lead to medical problems: • • • • Ozone absorbs ________________ light in the stratosphere Explain why our health will be affected if there is less ozone? Higher How exactly does ozone absorb UV light? It does this in 2 very simple reactions: 1. Ozone absorbs UV light and breaks down into an oxygen atom and an oxygen molecule: 2. The oxygen atom and molecule join back together to make ozone: How is the ozone layer depleted? Foundation • The formation of ___________ atoms in the ________________________ leads to the depletion of the ozone layer • CFC’s can only be removed very ______________ from the stratosphere Higher
  3. 3. • A covalent bond can break in one of 2 ways: 1. Unevenly to form ions 2. Evenly to form highly reactive free radicals • Only a small number of chlorine atoms are required because a chain reaction is set up. The chain of reactions: 1. High in the stratosphere, UV light breaks a C-Cl covalent bond in the CFC molecule to form free radicals 2. Chlorine free radicals then react with ozone, O3 3. The chlorine oxide molecule, ClO is very reactive and reacts with more ozone 4. The chlorine free radical that has been made goes and reacts with another ozone molecule and so the chain continues. One CFC molecule can react with a lot of ozone molecules. What is a safe alternative to CFC’s? Hydrocarbons can provide safe alternatives to CFCs Advantage: Disadvantage: HCFC’s can also be used. They break down in the __________atmosphere before reaching the ozone layer. They are ________ flammable than CFC’s but __________ than hydrocarbons.