Chemistry of the atmosphere

• Describe the proportions of gases in

  the modern atmosphere

  Around 80% of N2

  20% of O2

  ,

  • Small quantities of CO2

  , H2O, and noble gases
• Describe the Earth’s early atmosphere and how it was

  formed

  1. The Earth was hot when it was formed

  b) There was significant volcanic activity

  c) Gases have been released from these volcanoes

  d) These gases included CO2

  , N2

  , CH4

  , NH3

  , H2O
• How did the amount of oxygen

  in the atmosphere increase?

  Algae and plants produced the atmospheric O2 by photosynthesis, which can be represented by the equation: 6 CO2+ 6 H2O → C6H12O6+ 6 O2. As the amount of gradually O2 increased, there were more plants that produced more oxygen.
• How did the amount of carbon

  dioxide in the atmosphere

  decrease?


  1. Some CO2was dissolved in the oceans, where it reacted with metal ions to form insoluble carbonates, such as CaCO3, or was taken in by animals to become a part of skeleton. When animal dies, this becomes a sedimentary rock.
  2. Some CO2 was used in photosynthesis to make oxygen.
• What is the greenhouse effect? What are greenhouse gases? Give examples

  • Greenhouse gases in the atmosphere maintain temperatures on Earth high enough to support life.
  • They allow short wavelength radiation from the sun to pass through the atmosphere to the Earth’s surface, but absorb the outgoing long wavelength radiation from the Earth causing an increase in temperature.
  • Water vapour, carbon dioxide, and methane
• Why is the greenhouse effect necessary for life?

  The greenhouse effect is a natural phenomenon. Without it, the Earth would be too cold for life to exist.
• How have human activities led to an increase in greenhouse

  gases?

  Carbon dioxide – combustion and deforestation

  Methane – increased farming and decomposition in landfills
• What are the potential effects

  of global climate change?

  • sea level rise, which may cause flooding and increased coastal erosion

  • more frequent and severe storms

  • changes in the amount, timing and distribution of rainfall

  • temperature and water stress for humans and wildlife

  • changes in the food-producing capacity of some regions

  • changes to the distribution of wildlife species
• What is a carbon footprint?


  A carbon footprint is the total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service or event.
• What actions can be taken to reduce a carbon footprint?

  • increased use of alternative energy supplies

  • energy conservation

  • carbon capture and storage (where CO2 is trapped in solvents and stored

  underground)

  • carbon taxes and licences

  • carbon off-setting including through tree planting

  • carbon neutrality – zero net release.
• What are the challenges faced with reducing a carbon footprint?

  • scientific disagreement over causes and consequences of global climate change

  • lack of public information and education

  • lifestyle changes (people don’t want to give up their cars)

  • economic considerations (it will cost money)

  • incomplete international cooperation
• What are the advantages of complete combustion?

  • less soot (carbon particulates) is made with complete combustion

  • more heat per gram of fuel is released with complete combustion

  • poisonous carbon monoxide is not produced with complete combustion
• How is pollution caused by combustion?

  When a fuel burns, the gases released to the atmosphere include carbon dioxide, water (vapour), carbon monoxide, sulphur dioxide and oxides of nitrogen.

  Solid particles and unburned hydrocarbons may also be released that form

  particulates in the atmosphere.
• What are the issues regarding sulfur dioxide and oxides of nitrogen?

  Sulfur dioxide and oxides of nitrogen cause respiratory problems in humans and cause acid rain. Acid rain damages plants and buildings.
• What problems do particulates cause?

  Particulates, such as carbon particles, cause global dimming by reducing the

  amount of sunlight that reaches the Earth’s surface. Particulates cause health

  problems for humans because of damage to the lungs.