Paper 2: Chemistry of the atmosphere

• Describe the earths early atmosphere and how it was formed

  • The earth was hot when it was formed
  • There was significant volcanic activity
  • Gasses were released from these volcanoes
  • These gasses were: Carbon dioxide, Methane, water, ammonia(NH3)
• How did the amount of oxygen in the atmosphere increase

  • Algae and plants produce the earths oxygen through photosynthesis represented in the equation: carbon dioxide + water -> glucose + oxygen. As oxygen levels increased there were more plants to photosynthesise
• How did the amount of carbon dioxide in the earths atmosphere decrease

  • some carbon dioxide was dissolved in oceans where it mixed with metal ions to become insoluble carbonates such as calcium carbonate or taken in by animals which die and become sedimentary rocks
  • Some is used in photosynthesis to make oxygen
• Describe the proportions of the gasses in the earths atmosphere today, which have stayed constant for 200 million years


  78% Nitrogen

  21% Oxygen

  Small amounts of carbon dioxide, water vapour and Nobel gases such as argon
• The earths early atmosphere was much like mars and Venus atmosphere today
• Volcanoes realsed carbon dioxide, nitrogen, methane and ammonia
• Differences between the earths early and modern atmosphere

  - The earths early atmosphere contained mainly carbon dioxide but levels are now less than 1%

  - The earths early atmosphere contained very little oxygen but now it is at 21%
• Carbon produced from photosynthesis ends up in fossil fuels
• Fossil fuels are non renewable and formed over millions of years.
• Coal is formed from the remains of ferns and trees. If theses die in marshy wetlands they do not decompose due to a lack of oxygen or acidic conditions both preventing bacteria carrying out decomposition. Overtime the plant remains are covered with sediment and are compressed. High temperature and pressure creates coal
• carbon dioxide levels increased in oceans as it dissolved in water and carbons were precipitated producing sediment
• Oxygen levels initially increased via algae through photosynthesis 2.7 billion years ago
• once oxygen reached a certain level animals were able to evolve
• Carbon dioxide levels decreased due to: the formation of sedimentary rocks, fossil fuels containing carbon and photosynthesis
• Fossil fuels were formed over million years from the remains of ancient biomass, these remains were buried under layers of sand and mud. They were compressed under the ground and sea bed. As the temperature and pressure increased over time, they eventually turned into fossil fuels.
• Green house gasses are important because they maintain temperatures on earth high enough to support life
• Describe the green house effect

  • The sun emits UV radiation which passes through the earths atmosphere
  • The earth reflects some radiation but absorbs most of it
  • When the earths surface cools it emits this absorbed radiation in a longer wavelength called infra red
  • The radiation is absorbed by green house gasses which cannot leave the earths atmosphere
• How humans contribute to increase in carbon dioxide

  • burning fossil fuels in factories
  • burning fossil fuels in vehicles
  • deforestation
• How do Humans cause an increase in methane

  • cattle farming
  • rice farming
• Consequences of the green house effect

  • Global warming which leads to melting ice caps then a rise in sea levels
  • change in weather patterns
  • change in habitats
• why is it difficult for scientists to make arguments for the effects of the green house effect

  it is difficult to model such complex systems such as global climate change. This leads to simplified models and speculation.
• The media's views on climate change should be looked on with caution as it may be biased
• What is carbon footprint

  The total amount of carbon dioxide and green house gasses emitted over the full life cycle of a product, service or event
• How can carbon footprint be reduced

  • buying local produce
  • use public transport
  • limit meat consumption
• What is the main source of atmospheric pollutants

  Burning fossil fuels
• An impurity present in fuels

  Sulphur
• Carbon dioxide and water vapour are realised into the earths atmosphere as a result of complete combustion
• Carbon monoxide is realised into the earths atmosphere as a result of incomplete combustion
• Sulphur dioxide is released when a fuel is burnt as there are impurities which react with oxygen when burnt
• Oxides of nitrogen are realised when a fuel is burnt because nitrogen in the air reacts with oxygen when a fuel is burned under high temperatures in engines
• Solid particulates are formed when fuels are burned due to incomplete combustion
• Carbon monoxide is:

  • toxic
  • odourless
  • colourless
• Sulphur dioxide and Nitrogen oxides both cause respiratory problems and acid rain
• What issues are caused by carbon particulates

  • global dimming
  • health problems
• carbon footprint can be reduced by

  • buying local produce
  • use public transport
  • limit meat consumption
• how fossil fuels are formed

  1. remains of ancient biomass buried under layers of sand and mud
  2. compressed under the ground and sea bed
  3. as temperature and pressure increased over time they eventually turned into fossil fuels
• the formation of sedimentary rocks caused a deacsrese in CO 2 levels
• animals were able to evolve once oxygen reached a certain level