9-Chemistry of the atmosphere

• percentage of gases in our atmosphere now

  • nitrogen - 80 %
  • oxygen 20 %
  • other gases (argon/carbon dioxide) - less than 1 %
• 1 - evolution of the atmosphere

  1. 1st billion years - lots of volcanic activity producing:
  2. carbon dioxide, water vapour, nitrogen - small amounts of methane and ammonia
  3. water vapour condensed into liquid water forming oceans
  4. carbon dioxide dissolved in water forming carbon precipitates then sediments
• 2 - evolution

  1. 2.7 billion yrs ago - algae and green plants appeared
  2. photosynthesis - carbon dioxide declined and oxygen increased
  3. when plants and algae died they were buried in layers of sediment
  4. sediment compressed over millions of years forming sedimentary rock, oil, gas, trapping carbon from getting into the atmosphere

  • crude oil and natural gas - mainly plankton
  • sedimentary rock - coal - dead plant material, limestone - shells and skeletons
• planet earth is around 4.6 billion years old
• atmosphere is a layer of gases surrounding the earth that is held in place by gravity
• the greenhouse gases are

  • carbon dioxide
  • water vapour
  • methane
• • climate is the typical weather conditions in an entire region for a very long time
  • weather is the short term atmospheric conditions
• • global warming is the overall increase in the earth's temperature
  • climate change is a consequence of global warming and refers to the changes in climate
• greenhouse effect

  1. solar radiation from the sun passes the atmosphere and hits the earth
  2. some energy is reflected back towards space, some is absorbed by the earth and then reemitted to space
  3. the energy that is reflected back goes into space but most is absorbed by molecules in the atmosphere - greenhouse gases
  4. these molecules reemit the energy randomly, this is repeated
  5. the trapped energy makes the atmosphere warmer and more stable
• rise of greenhouse gases

  • carbon dioxide - burning fossil fuels, deforestation(less photosynthesis)
  • methane - farm animals produce it during digestion and is released into the atmosphere, producing waste that releases methane as it decomposes
• consequences of global warming - climate change

  • rare weather events (droughts, hurricanes, floods) will become more common and severe
  • rise in sea level (ice caps melting and water expanding when it warms up) can lead to seasonal flooding and the submersion of islands and coastal towns
  • species may not be able to adapt or migrate fast enough for the climate and become extinct causing biodiversity to decrease
• carbon footprint

  • a carbon footprint is the total amount of carbon dioxide and other greenhouse gases emitted from something
  • it can be either a product, service or event
  • pros - we can figure out how environmentally damaging things are and if they're worth the cost, identify most polluting activities and try to reduce emissions
  • cons - measuring carbon footprints is really hard and sometimes impossible
• you have to take into account - carbon footprints

  • how all the raw materials were sourced
  • the manufacturing process
  • the total amount of power it uses over it's lifetime
  • how it's disposed of
  • the emissions from transporting it
• carbon footprint - reducing emissions

  • using renewable energy sources - wind, solar, nuclear instead of fossil fuels
  • more efficient manufacturing process - use less energy, produce less waste
  • government - introducing new laws, taxing or limiting companies on how many greenhouse gases they emit
  • carbon capture technology - capture carbon before it is released into the atmosphere and store it deep underground where it can't escape
  • recycle the product
• carbon footprint - issues with reducing emissions

  • using renewable energy sources - expensive
  • government - if they prioritise the environment the economy might suffer
  • many of our existing products require fossil fuels
  • carbon capture - expensive
• complete combustion of hydrocarbons

  • hydrocarbon + oxygen = carbon dioxide + water
  • this is when there is plenty of oxygen
• incomplete combustion of hydrocarbons

  • releases carbon monoxide and particulates
  • this is when there is not enough oxygen
• • carbon monoxide - if breathed in, it diffuses into blood and binds to haemoglobin so less oxygen can be carried around the body leading to a coma, fainting, death, it's colourless and odourless so is hard to detect
  • releases particulates (soot) - can lead to respiratory problems, can form smog that reflects sunlight back into space (global dimming)
• hydrocarbons with impurities

  • releases sulphur dioxide and nitrogen oxides
  • this happens when impurities in hydrocarbons are burned and the sulphur oxidises and nitrogen reacts with oxygen
• • sulphur dioxide - causes respiratory problems, dissolve in clouds to form dilute sulphuric acid - acid rain
  • nitrogen oxide - doesn't usually happen as high temperatures are required such as in internal combustion engines, causes respiratory problems, dissolve in clouds to form dilute nitric acid - acid rain

  acid rain damages buildings and statues, corrodes metals, damages plants by landing on it or making the soil acidic