Earth & atmospheric science

• What formed the Earth’s early atmosphere?

  • gases produced by volcanic activity
• How did the amount of carbon dioxide in the atmosphere decrease?

  • dissolved in seas/oceans
  • some incorporated into sea animals' shells
  • absorbed during photosynthesis
• Describe the chemical test for oxygen

  • use a glowing splint and observe if it relights once inserted into the gas
• How has the amount of water vapour in the atmosphere decreased?

  • the Earth cooled
  • so water vapour condensed to form oceans/seas
• Why did the amount of oxygen in the atmosphere gradually increase?

  • plants evolved
  • photosynthesis, which releases oxygen
  • human effect of reforestation
• Why has the amount of carbon dioxide in the atmosphere increased?

  • burning fossil fuels
  • agriculture
  • deforestation means less is being absorbed during photosynthesis
  • increase in sea temperature releases the dissolved carbon dioxide
  • respiration
• What was the Earth’s early atmosphere thought to

  contain?

  • little or no oxygen
  • a large amount of carbon dioxide
  • water vapour
  • small amounts of other gases
• What is the greenhouse effect?

  • gases in the atmosphere, including carbon dioxide, methane and water vapour, absorb heat radiated from the Earth, subsequently releasing energy which keeps the Earth warm (re-radiate heat back into the atmosphere)
• What is the relative amount of gases in today's atmosphere?

  • oxygen: large (21%)
  • carbon dioxide: little (less than 0.5%)
  • water vapour: little (0%-4%)
  • other gases: large (78% nitrogen)