chemistry of the atmosphere

• What are the main gases in the atmosphere?

  80% nitrogen and 21% oxygen
• How long have the proportions of gases in the atmosphere been stable?

  For 200 million years
• Why is evidence about the Earth's early atmosphere limited?

  Due to the time scale of 4.6 billion years
• What does one theory suggest about the Earth's early atmosphere?

  It was formed by gases from volcanic activity
• What gases may have been present in the early atmosphere?

  CO2, N2, CH4, and NH3
• What happened to water vapor in the early atmosphere?

  It condensed to form the oceans
• How did CO2 levels decrease in the early atmosphere?

  CO2 dissolved in water and formed sediments
• What is the only theory of the early atmosphere you need to know?

  The theory involving volcanic gases
• How did algae and plants contribute to oxygen levels?

  They produced O2 through photosynthesis
• What is the photosynthesis equation for producing glucose and oxygen?

  6CO2 + 6H2O -> C6H12O6 + 6O2
• When did algae first produce oxygen?

  About 2.7 billion years ago
• What happened to oxygen levels over the next billion years?

  Oxygen levels gradually increased
• How did algae and plants decrease CO2 levels in the atmosphere?

  By photosynthesis and forming sedimentary rocks
• How are fossil fuels produced?

  From the remains of decayed plants and animals
• What is the role of photosynthesis in the atmosphere?

  It decreases CO2 and increases O2
• What is a major source of atmospheric pollutants?

  Combustion of fuels
• What elements do most fuels contain?

  Carbon and/or hydrogen, and some sulfur
• What do greenhouse gases maintain on Earth?

  Temperatures high enough to support life
• What gases are released when a fuel burns?

  Carbon dioxide, water, carbon monoxide, nitrogen oxides
• What can be released during incomplete combustion?

  Soot, carbon monoxide, unburnt fuel
• Which gases are considered greenhouse gases?

  Water vapour, CO₂, and CH₄
• What happens during the combustion of hydrocarbons?

  Carbon and hydrogen are oxidised to form CO2 and water
• What is the greenhouse gas effect?

  • Electromagnetic radiation from the sun passes through the atmosphere
  • Earth absorbs some radiation and warms up
  • Some heat is radiated as infrared radiation
  • Greenhouse gases absorb some IR radiation
  • Atmosphere warms up, leading to the greenhouse effect and global warming
• What is carbon monoxide?

  A toxic, colourless, and odourless gas
• What human activities increase greenhouse gases?

  Driving, consuming electricity, raising livestock
• What problems do sulfur dioxide and nitrogen oxides cause?

  Acid rain and respiratory problems in humans
• What gases are increased by driving and consuming electricity?

  CO₂
• What effects do particulates have on the environment?

  Cause global dimming and health problems
• What greenhouse gas is associated with raising livestock?

  CH₄
• What are the main atmospheric pollutants from fuel combustion?

  • Carbon dioxide
  • Water (vapour)
  • Carbon monoxide
  • Oxides of nitrogen
  • Solid particles
  • Unburned hydrocarbons
• What greenhouse gas is produced by the decay of organic waste?

  CH₄
• What are the properties and effects of key atmospheric pollutants?

  • Carbon monoxide: toxic, colourless, odourless
  • Sulfur dioxide and nitrogen oxides: cause acid rain and respiratory issues
  • Particulates: cause global dimming and health problems
• What do many scientists believe about human activities and Earth's temperature?

  They will cause an increase in temperature
• Why is it difficult to model global climate change?

  Because it involves complex systems
• What can result from simplified models of climate change?

  Speculation and biased opinions in media
• What is a major cause of climate change?

  An increase in average global temperature
• What are the potential effects of global climate change?

  • Extinction of species
  • Raising sea levels from melting ice caps
  • Migration due to drought or flooding
  • Decrease in crop yield for major crops
• What is a carbon footprint?

  Total amount of CO₂ and greenhouse gases emitted
• How can the carbon footprint be reduced?

  By reducing emissions of CO₂ and CH₄
• What is one way to reduce electricity consumption?

  Use less electricity or alternative sources