Topic 9 - Chemistry of the Atmosphere

• How has the Earth's atmosphere changed in the past 200 million years?

  It has stayed roughly the same
• What are the two main gasess in the Earths atmosphere?

  NitrogenOxygen
• What is the most abundant gas in the earth's atmosphere?

  Nitrogen
• What percentage of the atmosphere is made up of nitrogen?

  80%
• What percentage of the atmosphere is oxygen?

  20%
• give 3 gases other than oxygen and nitrogen that are present in the earth's atmosphere

  carbon dioxidewater vapournoble gasessThere are only very small amounts of these
• What is the most popular theory for the formation of the early atmosphere?

  Intense volcanic activity, which occured for a billion years after the earth's formation, released gases which formed the early atmosphere
• What was probably the composition of the early atmosphere?

  Mainly carbon dioxide with little to no oxygen. Small amounts of methane, water vapour and ammonia
• How did nitrogen build up in the early atmosphere?

  It was constantly released by volcanic activity
• How did the amount of water vapour in the early atmosphere decrease?

  It cooled and condensed to become the oceans
• What are the two ways the amount of carbon dioxide decreased in the early atmosphere?

  absorption by the oceansabsorption by plants and algae
• How did the oceans decrease the amount of carbon dioxide in the early atmosphere?

  When the oceans formed, a lot of carbon dioxide dissolved into them and formed carbonate precipitates that formed sediments on the sea bed
• What is sediment?

  carbon precipitates found on the seabed
• How did green plants and algae redice the amount of carbon dioxide in the early atmosphere?


  They used the carbon dioxide in the atmosphere for photosynthesis
• WHat happened to the levels of carbon dioxide in the early atmosphere

  It decreased
• What happened to the levels of oxygen in the early atmosphere?

  It increased
• What happened to the levels of nitrogen in the early atmosphere?

  It increased
• Give two types of sedimentary rock?

  CoalLimestone
• How was limestone formed?

  deposits of calcium carbonate from the shells and skeletons of marine organismsdissolved carbon dioxide from the atmosphere
• What happens when plants, plankton and marine animals die?

  They sink to the sea bed and get buried under layers of sediment where they are compressed and oil and gas. This locks away carbon and reduces its amount in the atmosphre
• How is crude oil formed?

  Deposits of plankton compressed by sediment over millions of years
• How is natural gas formed?

  Deposits of plankton compressed by sediment over millions of years
• How is coal formed?

  Formed from compressed plant deposits
• How is limestone formed?

  Formed from calcium carbonate deposits from the shells and exoskeletons of marine organisms and by carbon dioxide form the early atmosphere
• How has the level of oxygen in the atmosphere increased?

  Green plants and algae produce oxygen as a product of photosynthesis
• What is photosynthesis?

  The process that of plants using light to convert carbon dioxide and water into sugars
• What is the equation for photosynthesis?

  6CO2 + 6H2O → C6H12O6 + 6O2
• Why is it important that the levels of oxygen in the atmosphere increased?

  It allowed more complex organisms to evolve
• Why is it hard to prove theorieds about how the atmosphere evolved?


  The atmosphere evolved a very long time ago so there is very little evidence to backup any theories and work out what happened
• Why are there many theories for how the atmosphere evolved?

  Due to a lack of evidence and no definite proven theory
• Give three examples of greenhouse gases

  MethaneCarbon dioxideWater
• Describe how greenhouse gases warm the atmosphere

  The sun emits short wavelength radiation which passes through the atmosphereThis reaches the earth's surface, is reabsorbed and re emmited as longer wave radiationThe atmospher absorbs this and radiates it in all direction sincluding back to Earth
• What is the greenhouse effect?

  The process of how greenhouse gases warm the surface of the Earth
• What 2 factors have caused humans to burn more fossil fuels?

  Very fast population increaseIndustrilisation
• Give three ways humans are releasing more carbon dioxide into the atmosphere

  deforestationburning fossil fuelslandfill sites
• How does deforestation increase carbon dioxide levels?

  The trees cut down used to absorb carbon dioxide for photosynthesis
• How does burning fossil fuels increase carbon dioxide levels?

  Carbon previously 'locked up' in the fuels is being released
• How does landfill increase carbon dioxide levels?


  Waste breaking down and being burnt
• How are humans increasing the amount of methane in the atmosphere?

  some food production
• Give two examples of how food production is increasing the amount of methane in the atmosphere

  Cow farmingRice Paddy Fields