Chemistry of the atmosphere

• How long have the properties of the gases in the atmosphere been like today?

  200 million years
• What are the gases found in today's atmosphere?

  • nitrogen
  • oxygen
  • carbon dioxide
  • water vapour
  • noble gases
• What are the percentages of the gases in today's atmosphere?

  Nitrogen = 80%

  Oxygen = 20%

  other gases (including CO2, water vapour and noble gases) = <1%
• What timescale is evidence for the early atmosphere limited to?

  4.6 billion years ago
• What theory is given for the earth's early atmosphere?

  1. First billion years intense volcanic activity released lots of carbon dioxide and water vapour (alongside other gases such as methane, nitrogen and ammonia)
  2. When the earth cooled, the water vapour was able to cool and condensed to form oceans
  3. Overtime, carbon dioxide levels started to decrease
  4. Algae and plants evolved
  5. Oxygen levels started to increase and animals were then able to evolve
• What planets is the earth's early atmosphere suggested to be like?


  Mars and Venus, consisting mainly of carbon dioxide and little or no oxygen
• What other gases were released by volcanoes?

  • Nitrogen (N2)
  • Methane (CH4)
  • Ammonia (NH3)
• What are the four ways carbon dioxide levels were reduced?

  1. dissolved into the oceans
  2. plants and algae took it in for photosynthesis
  3. carbonates precipitated producing sediments
  4. locked in fossil fuels
• How did the percentage of oxygen increase in the early atmosphere?

  Algae and plants released it during photosynthesis
• What is the word equation for photosynthesis?

  Carbon dioxide + water -> glucose + oxygen
• What is the balanced symbol equation for photosynthesis?

  6CO2 + 6H2O → C6H12O6 + 6O2
• When did algae first appear?

  2.7 billion years ago
• What did the increase in oxygen from algae and plants lead to?


  Enabled animals to evolve
• What useful substances have been formed as carbon dioxide decreased?

  • Limestone
  • coal
  • crude oil
  • natural gas
• What type of gas maintains the temperature on earth to be high enough to support life?

  Greenhouse gases
• Examples of greenhouse gases

  Water vapour = H2O (g)

  carbon dioxide = CO2

  methane = CH4
• Describe the greenhouse effect (1-2)

  1. The sun emits short wavelength radiation which passes

  through the Earth’s atmosphere (contains greenhouse

  gases) and is absorbed by the Earth’s surface.

  2. The Earth then emits any excess radiation back as long

  wavelength radiation towards space.
• Describe the greenhouse effect (3-4)

  3. Some of the long wavelength radiation makes its way

  through but some of this is trapped by greenhouse gases

  (they absorb long wavelength radiation but let through

  the short wavelengths).

  4. This is then emitted back down to the Earth’s surface

  causing it to heat up more, this process repeats causing

  the Earth’s average temperature to increase.
• What greenhouse gases are increased due to human activity?

  Carbon dioxide and methane
• What human activities are increasing the level of carbon dioxide and methane?

  Carbon dioxide increasing because:

  • Burning fossil fuels

  • Deforestation reduces carbon dioxide taken in by photosynthesis

  Methane increasing because:

  • Farming cattle

  • Farming rice paddy fields

  • Landfill sites (rubbish decomposes and releases methane)

  • Swamps
• What do scientists believe human activity will do to the temperature of the earth?

  Increase it, leading to climate change
• What is the temperature of the Earth increasing normally referred to as?

  Global warming
• Why is it difficult to predict global warming?

  Based on simply models, speculation and opinion presented in media
• What is the issue with climate change presented in the media?

  Based on opinion, speculation, only parts of evidence reported and can be biased
• What is causing climate change?

  Increase in average global temperature
• What are the main four potential effects of global climate change?

  • Glacier and polar ice caps melting

  • Sea levels rising

  • Patterns in rainfall changing leading to: floods or droughts

  • Habitats changing
• What is a 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 a carbon footprint be reduced?

  By reducing emissions of carbon dioxide and methane
• How can we reduce the emissions of carbon dioxide and methane?

  Can be difficult and some people don’t want to.

  • Reduce use of cars (cycle/ walk instead)

  • Eat less meat

  • Ensure any tress cut down are replanted

  • Recycle and reuse materials

  • Install solar panels in your home
• What is a major source of atmospheric pollutants?

  Combustion of fuels
• What do most fuels contain?

  Carbon, hydrogen and some contain sulphur
• What gases can be released into the atmosphere when a fuel is burnt?

  Carbon dioxide (CO2)

  Water vapour (H2O(g))

  Carbon monoxide (CO)

  Sulphur dioxide (SO2)

  Oxides of nitrogen (NO, NO2, N2O)

  Others: Particulate (PMx) these are microscopic particles
• What do particulates contribute to?

  Global dimming (smog)
• How are oxides of nitrogen produced when burning a fuel?

  High temperature in car engines cause oxygen and nitrogen in the air to react: N2 + O2 → 2NO
• How is sulfur dioxide produced when burning a fuel?

  Fuels contain sulfur as an impurity, when the fuel is burnt the sulphur reacts with oxygen to form sulphur dioxide: S + O2 → SO2
• What do oxides of nitrogen and sulfur dioxide lead to?

  Acid rain

  Respiratory problems
• What does carbon dioxide contribute to and why?

  Global warming as it's a greenhouse gas
• What are the issues with the production of carbon monoxide?

  Is a toxic gas, it prevents blood from carrying oxygen to your cells for respiration
• Why is it hard to detect if carbon monoxide is formed?

  Is odourless and colourless so can’t be seen