trial

• Gases in the Earth's atmosphere

  • Nitrogen
  • Oxygen
  • Carbon dioxide
  • Water vapour
  • Noble gases
• Proportions of gases in the Earth's atmosphere

  • Nitrogen 80%
  • Oxygen 20%
  • Small proportions of other gases
• Evidence for the Earth's early atmosphere is limited because of the timescale of 4.6 billion years
• Gases released from volcanoes in the first billion years

  • Nitrogen
  • Carbon dioxide
  • Water vapour
  • Small amounts of ammonia and methane
• Formation of the oceans

  Water vapour in the atmosphere condensed
• Carbon dioxide in the earlier atmosphere

  Decreased as it dissolved in the oceans and carbonates were precipitated
• Oxygen was not present in the atmosphere 4.6 billion years ago
• The composition and evolution of the Earth's Atmosphere (Part 1)
• Name 4 gases in the Earth's atmosphere.

  • Nitrogen, oxygen, other gases such as carbon dioxide, water vapour and noble gases.
• Proportions of gases in the Earth's atmosphere

  Nitrogen 80%; Oxygen 20%; small proportions of other gases.
• Why is evidence for the Earth's early atmosphere limited?

  The timescale of 4.6 billion years.
• What gases are believed to have been released from volcanoes during the first billion years of the Earth's existence?

  • Nitrogen, carbon dioxide, water vapour; small amounts of ammonia and methane.
• How did the oceans form?

  Water vapour in the atmosphere condensed.
• Why did the amount of carbon dioxide in the earlier atmosphere decrease?
• What gas in the current day atmosphere was not present in the atmosphere 4.6 billion years ago?
• The composition and evolution of the Earth's Atmosphere Part 2
• How oxygen increased

  Organisms evolved that changed the atmosphere in a significant way. Algae and plants produced the oxygen that is now in the atmosphere by photosynthesis.
• How carbon dioxide decreased

  Algae and plants decreased the percentage of carbon dioxide in the atmosphere by photosynthesis. Carbon dioxide was also decreased by the formation of sedimentary rocks and fossil fuels that contain carbon.
• When did oxygen first start appearing in the atmosphere and which organism was responsible?
• Other than photosynthesis what other factors decreased the level of carbon dioxide in the atmosphere?
• Describe the main changes to the atmosphere over time and the likely causes of these changes.

  Intense volcanic activity – water vapour, carbon dioxide, nitrogen, ammonia, methane released. Water vapour condensed to form oceans. Atmosphere mostly carbon dioxide; nitrogen slowly building up over time. Carbon dioxide dissolved in oceans; carbonates precipitated producing sediments. Carbon dioxide levels in atmosphere drop. Photosynthesis – algae produce oxygen. Plants evolved, levels of carbon dioxide reduced, levels of oxygen increased; animals evolved. Carbon dioxide levels dropped during the formation of sedimentary rock (from sediments) and fossil fuels (from organisms).
• Carbon dioxide and methane as greenhouse Gases Part 1
• Name 3 greenhouse gases.

  • Carbon dioxide, water vapour, methane.
• Link between greenhouse gases and temperature of Earth

  Greenhouse gases maintain temperatures on Earth high enough to support life.
• Human activities which increase carbon dioxide in atmosphere

  • Burning fossil fuels, deforestation.
• Human activities which increase methane in atmosphere

  • Farming of livestock, landfills.
• What do many scientists believe about human activities and temperature of Earth's atmosphere?
• Why are there issues surrounding modelling human impact on climate change?

  It is difficult to model these changes. Simplified models are generated leading to speculation and opinions presented in the media that may be based on only part of the evidence and be biased.
• Carbon dioxide and methane as greenhouse Gases Part 2
• Major cause of climate change

  An increase in average global temperature.
• Possible effects of climate change

  • Rising sea levels causing flooding, droughts, desertification, ice caps melting.
• Carbon footprint

  The total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of the product, service or event.
• How to reduce carbon footprint

  Reducing emissions of carbon dioxide and methane.
• Common atmospheric pollutants and their sources
• Main elements in most fuels

  Hydrogen and carbon.
• Gases released when fuel is burned

  • Carbon dioxide, water vapour, carbon monoxide, sulfur dioxide and oxides of nitrogen.
• Gases that can lead to acid rain

  • Sulfur dioxide, oxides of nitrogen.
• Other substances released during combustion to form particulates

  • Solid particulates, unburned hydrocarbons.
• Balanced equation for complete combustion of pentane C5H12

  C5H12 + 8O2 → 5CO2 + 6H2O
• Substances formed in incomplete combustion of pentane

  • Water and carbon monoxide and/or soot