CHEM OF THE ATMOSPHERE

• what are the proportions of different gases in the atmosphere?


  - 80% nitrogen

  - 20% oxygen

  - small proportions of various other gases including carbon dioxide, water vapor and noble gases
• for how long have the proportion of gases been the same?

  200 million years
• why is evidence of the early atmosphere limited?

  because of the time scale of 4.6 billion years
• what is phase 1 of earth's early atmosphere?

  - intense volcanic activity released gases that formed the early atmosphere and water vapor condensed to form the oceans

  - the atmosphere consisted of mainly carbon dioxide with little to no oxygen

  - volcanoes produced nitrogen as well as methane and ammonia
• what is phase 2 of earth's early atmosphere?

  - when the oceans formed, carbon dioxide was dissolved and the carbonates were precipitated producing sediments

  - green plants and algae evolved and absorbed some of the carbon dioxide
• how did carbon dioxide levels decrease?


  - algae and plants, by photosynthesis

  - the formation of sedimentary rocks and fossil fuels that contain carbon
• what is limestone?

  a sedimentary rock made of calcium carbonate deposits from the shells and skeletons of marine animals
• what is coal?

  a sedimentary rock made from thick plant deposits
• what is crude oil and natural gas?

  fossil fuels formed from deposits of plankton, which form reservoirs under the seabed when they get trapped in rocks
• what was phase 3 of earth's early atmosphere?

  green plants and algae first produced oxygen by photosynthesis about 2.7 billion years ago
• what is the equation for photosynthesis?

  6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
• which are the greenhouse gases?

  - carbon dioxide

  - methane

  - water vapor
• what do greenhouse gases do?

  maintain temperatures on earth high enough to support life
• what is the greenhouse effect in terms of the interaction of short and long wavelength radiation with matter?

  - greenhouse gases don't absorb incoming short wavelength radiation from the sun

  - they absorb long wavelength radiation (thermal radiation) that gets reflected back off the earth

  - then they re-radiate from all directions
• what are two human activities that increase the amounts of carbon dioxide and methane?

  - deforestation: less CO₂ is removed by photosynthesis

  - agriculture: more farm animals, more methane
• why is there speculation of climate change?

  it is difficult to model such complex systems, which leads to simplified models, speculation and opinions in the media that may be based on only parts of the evidence and which may be biased
• what are four potential effects of global climate change?

  - polar ice caps melting: an increase in sea levels, flooding, coastal erosion

  - changes in rainfall patterns: some regions may get too little or too much water

  - frequency and severity of storms will increase

  - changes in temperature can affect wild animals and their distribution
• what is carbon footprint?


  the total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service or event
• how can the emissions of carbon dioxide and methane be reduced?

  - using renewable energy sources

  - cap on greenhouse gas emissions

  - using more efficient processes to conserve energy and cut waste
• why are actions for reducing carbon footprint limited?

  - could affect economic growth of communities

  - still a lot of work to be done on alternative technologies

  - hard for countries to make international agreements
• what do most fuels contain?

  - carbon/hydrogen

  - sometimes sulfur
• which gases may be released into the atmosphere when a fuel is burned, and why?

  because of incomplete combustion of hydrocarbons:

  - carbon dioxide

  - water vapor

  - carbon monoxide

  - sulfur dioxide

  - oxides of nitrogen

  - solid particles

  - unburned hydrocarbons
• what are the properties and effects of carbon monoxide?


  - toxic

  - colorless

  - odorless

  - deadly
• what are the properties and effects of sulfur dioxide and oxides of nitrogen?


  - respiratory problems

  - acid rain: kills plants, damages buildings, statues
• what are the effects of particulates?

  - global dimming

  - health problems (respiratory)