Topic 9- chemistry (atmosphere)

• Theories for how the Earth's atmosphere evolved


  1. Volcanoes gave out gases

  2. Oceans, algae and green plants absorbed carbon dioxide

  3. Green plants and algae produced oxygen
• Early atmosphere


  Mostly carbon dioxide, with virtually no oxygen
• Volcanic activity released nitrogen, water vapour, methane and ammonia
• Carbon dioxide removal from early atmosphere


  1. Dissolved in oceans

  2. Formed carbonate precipitates in sediments

  3. Absorbed by green plants and algae for photosynthesis

  4. Locked up in rocks and fossil fuels
• Coal, crude oil and natural gas are 'fossil fuels' formed from deposits of plants and plankton
• Limestone is a sedimentary rock mostly made of calcium carbonate deposits from marine organisms
• Oxygen production by green plants and algae


  Photosynthesis converts carbon dioxide and water into glucose and oxygen
• Atmosphere reached current composition of 80% nitrogen, 20% oxygen and small amounts of other gases around 200 million years ago
• Greenhouse gases


  Gases like carbon dioxide, methane and water vapour that act like an insulating layer in the Earth's atmosphere
• Greenhouse gases absorb long wavelength radiation reflected from the Earth


  This results in warming of the Earth's surface (greenhouse effect)
• Human activities affecting greenhouse gas levels


  • Deforestation
  • Burning fossil fuels
  • Agriculture
  • Waste disposal
• Increasing carbon dioxide levels are linked to climate change
• It's hard to fully understand the Earth's complex climate system and make accurate predictions
• Potential consequences of climate change


  • Melting of polar ice caps and rising sea levels
  • Changes in rainfall patterns and food production
  • Increased frequency and severity of storms
  • Changes in distribution of wild species
• Carbon footprint


  Mass of carbon dioxide and other greenhouse gases released over the full life cycle of something
• Measuring total carbon footprint can be very difficult due to the many factors involved
• Ways to reduce carbon footprints


  • Use renewable energy or nuclear power instead of fossil fuels
  • Use more efficient processes to conserve energy and reduce waste
  • Government policies like carbon taxes and emissions trading
  • Carbon capture and storage technology
• Reducing greenhouse gas emissions is still difficult due to technological, economic and political challenges
• Combustion of fossil fuels releases not just carbon dioxide, but also other gases and particles like nitrogen oxides, sulfur dioxide and carbon monoxide
• Combustion of fossil fuels


  1. Complete combustion with plenty of oxygen produces carbon dioxide and water

  2. Incomplete combustion with insufficient oxygen produces carbon monoxide and particulates
• Particulates


  • Can cause respiratory problems if inhaled
  • Reflect sunlight and cause global dimming
• Carbon monoxide


  Binds to haemoglobin in blood, reducing oxygen transport around the body
• Formation of acid rain


  1. Sulfur dioxide and nitrogen oxides mix with clouds to form sulfuric acid and nitric acid

  2. Acid rain damages plants, buildings and causes metal corrosion
• Sulfur dioxide and nitrogen oxides can also cause respiratory problems in humans
• greenhouse gases are carbon dioxide, methane, nitrous oxide, water vapour and fluorinated gases
• the greenhouse effect is the warming of earth's surface due to gases trapping heat
• carbon dioxide is produced by burning fossil fuels, deforestation and respiration