C9 - Chemistry of the Atmosphere

• In the Earth's early atmosphere, most of the surface was covered by volcanoes.
• The gases in the Earth's early atmosphere were:

  • Water Vapour - H₂O (74%)
  • Carbon Dioxide - CO₂ (12%)
  • Nitrogen - N₂ (5%)

  And other gases (9%):

  Hydrogen - H₂

  Methane - CH₄

  Ammonia - NH₃
• In today's atmosphere, most of the surface of the Earth is covered by oceans.
• The gases in Today's Atmosphere are:

  • Nitrogen - N₂ (78%)
  • Oxygen - O₂ (21%)

  Other gases (1%):

  • Methane - CH₄
  • Water Vapour - H₂O
  • Carbon Dioxide - CO₂
  • Argon - Ar
• The Earth's early atmosphere was weakly reducing (Reduction of Hydrogen)
• The Earth's modern atmosphere is oxidising (Adding of Oxygen)
• Carbon Dioxide dissolved in the oceans to form sedimentary rock.
• Ammonia + Water Vapour → Nitrogen

  NH₃ + H₂O → N₂
• Limestone is a sedimentary rock.
• Coal, Oil and Natural Gas are all fossil fuels.
• Fossil fuels are made from the remains of dead organisms.
• One use of fossil fuels is to provide heat (Heating and Cooking).
• Limestone is made up of calcium carbonate and is formed from the remains of dead sea creatures that have fallen to the bottom of the ocean.
• Limestone and fossil fuels are finite and non-renewable because they take millions of years to form.
• The greenhouse gases are:

  • Water Vapour - H₂O
  • Carbon Dioxide - CO₂
  • Methane - CH₄
• In the atmosphere, greenhouse gases absorb heat energy. This stops some heat energy escaping into space. This keeps the Earth warmer than it would be. Greenhouse gases include carbon dioxide and methane.
• Weather is the state of the atmosphere at a given time and place. It is measured in terms of factors such as temperature, rainfall, humidity and cloudiness.
• Climate is the average weather for a region over a long period of time, usually 30 years.
• Global warming consequences:

  • Sea Levels rise
  • some extinct
  • Extreme weather conditions e.g. draughts and floods
  • Increase in disease like malaria
  • Water shortages
  • Food shortages
• Carbon footprint is the total amount of carbon dioxide (and other greenhouse gases) are emitted.
• Many of the Earth's resources are finite.
• Humans use the Earth's natural resources for a number of purposes, including:

  1. Energy and fuels for warmth
  2. Building materials for shelter
  3. Food through farming
  4. Fuels for transport
  5. Materials for clothing
• Sustainable - for future generations
• • Finite resources from the Earth's crust, oceans and atmosphere will one day run out. They can be processed to provide energy and useful material.
• Renewable resources are those which will not run out in the foreseeable future.
• Potable water is not pure water because it almost always contains dissolved impurities.
• For water to be potable it must have sufficiently low levels of dissolved salts and microbes.

  This is because:

  • Dissolved salts can sometimes be harmful for humans.
  • Microbes can cause illnesses.
• Potable water can be made using fresh water & sea water.
• Most potable water in the UK is produced from naturally occurring fresh water by:

  1. Passing the water through filter beds to remove insoluble particles
  2. Sterilising the water to kill microbes

  The methods of sterilisation include chlorine, ozone and ultraviolet light.
• Potable water can be made from sea water, through a process known as desalination.