C13 - The Earth's atmosphere

• how was the earths atmosphere formed?

  one theory suggests that during the first billion years of earths existence there was an intense volcanic activity that released gases that formed the early atmosphere and water vapour that condensed to form oceans
• what are the proportions of gases in the atmosphere?

  approx 80% nitrogen

  approx 20% oxygen

  small proportions if various other gases such as carbon dioxide, water vapour and noble gases
• volcanos produced nitrogen which gradually built up in the atmosphere and there may have been small proportions of methane and ammonia
• when the oceans formed, CO2 dissolved in water and carbonates were precipitated producing sediments reducing the amount of CO2 in the atmosphere
• what is another theory of how water on earth came about?

  comets could have brought water to the earth as icy comets rained down on the earths surface melting and adding to its water supplies
• what are the specifics of how water formed from volcanos?

  the volcanos released gases including water vapour which formed the early atmosphere

  as the atmosphere began to cool, the water condensed and fell as rain
• how did oxygen levels increase?

  algae evolved and could use energy from the sun to make their own food by photosynthesis producing oxygen as a waste product

  plants evolved and colonised most of the earths surface causing an oxygen richer atmosphere
• how did CO2 levels decrease?

  the algae and plants had evolved and decreased the % of CO2 via photosynthesis

  it was also due to the formation of sedimentary rocks and fossil fuels that contain carbon
• coal is classed as a sedimentary rock and was formed from thick deposits of plant material such as ancient trees and ferns. when the plants died in swamps, they were buried, in the absence of oxygen and compressed over millions of years
• crude oil and natural gas were formed from the remains of plankton deposited in muds on the seabed. these were covered by sediments that became layers of rock when compressed over millions of years. the crude oil and natural gas formed is found trapped beneath these layers
• what is the equation for how methane is removed from the atmosphere?

  CH4+²O2 -> CO2 +²H2O
• what is the equation for how ammonia is removed from the atmosphere?

  ⁴NH3 +³O2 -> ²N2 + ⁶H2O
• What are the main greenhouse gases in the Earth's atmosphere?

  Carbon dioxide, methane, and water vapor
• How do greenhouse gases warm the Earth?

  They absorb infrared radiation emitted by the Earth
• What percentage of energy reaching the Earth is reflected back into space?

  Almost 30%
• What is the chemical equation for the combustion of propane?

  CH₈ + 5O₂ → 3CO₂ + 4H₂O
• What are some sources of methane emissions?

  Swamps, rice fields, and cattle waste
• What has caused the increase in carbon dioxide levels over the past century?

  Increased fossil fuel usage
• What is the greenhouse effect and its implications?

  • Greenhouse gases trap heat in the atmosphere
  • They allow short-wavelength radiation to pass
  • They absorb long-wavelength infrared radiation
  • Resulting in an increase in Earth's temperature
• What are the impacts of increased greenhouse gases on climate change?

  • Enhanced greenhouse effect leads to global warming
  • Changes in weather patterns and climate extremes
  • Melting ice caps and rising sea levels
  • Threats to biodiversity and ecosystems
• What happens to carbon dioxide solubility as temperature rises?

  It becomes less soluble in water
• What is the effect of rising temperatures on oceans as CO₂ sinks?

  Oceans become less effective as CO₂ sinks
• What can scientists analyze from trapped air in ice cores?

  Changes in gas composition over time
• What are the key points regarding carbon dioxide levels and climate change?

  • Carbon dioxide levels have risen recently.
  • Difficult to predict climate effects of greenhouse gases.
  • Majority of evidence supports human activity increases temperature.
• what is a carbon footprint?

  the carbon footprint of a product, service, or event is the total amount of CO2 and other greenhouse gases emitted over its full life cycle
• what are issues that have arised from climate change?

  rising sea levels due to warmer oceans and so melting ice caps

  more frequent, severe storms

  changes in temperature, amount, timing and distribution of rainfall

  changes in distribution of wildlife species
• how can green house gases be reduced?

  reducing the use of fossil fuels by using alternative sources of energy that conserve energy
• what happens when there is not enough oxygen in an engine?

  incomplete combustion and instead of CO2 being released, CO is also formed
• what are problems with producing carbon monoxide (CO) as a by-product of incomplete combustion?

  it is a toxic, colourless odorless gas which if breathed in, binds to your red blood cells and travels around your body instead of oxygen taking up sites of haemoglobin that usually bond to oxygen
• what are symptoms of CO poisoning?

  a victime may:

  • feel drowsy
  • lose consciousness
  • die
• what other gas is produced due to high temperature engines?

  nitrogen oxides as the nitrogen gas in the air reacts with oxygen

  nitrogen oxides are toxic and can triger asthma and cause acid rain
• what causes global dimming?

  particulates (tiny solid particles containing carbon and unburnt hydrocarbons) get carried into the air and travel into the upper atmosphere reflecting sunlight back into space
• what causes particulates to build up?

  diesel engines burn hydrocarbons with bigger molecules than those in petrol engines. when these large molecules react with oxygen in an engine they do not always burn completely causing particulates
• what causes sulfur dioxide to build up in the atmosphere?

  the combustion of sulfur impurities in fossil fuels