atmosphere

• For how long has the proportions of the different gases in the atmosphere remained much the same?

  200 million years
• What is the composition of today's atmosphere?

  Approximately 80% Nitrogen, approximately 20% oxygen and small proportions of various other gases, including carbon dioxide, water vapour and noble gases
• Why do we not know the composition of the Earth's early atmosphere?

  Evidence is limited because of the time scale of 4.6 billion years
• What does one theory suggest formed the main atmosphere in the first billion years of the earth's existence?

  Intense volcanic activity releasing carbon dioxide, water vapour and little or no oxygen into the atmosphere
• What does one theory suggest the Earth's early atmosphere was like?

  Mars' and Venus' atmospheres today
• In addition to carbon dioxide and water vapour what other gases could have been produced by volcanic activity?

  Nitrogen and small proportions of methane and ammonia
• What caused the amount of nitrogen to gradually increase in the atmosphere?

  Volcanic activity
• What formed the oceans on the Earth?

  Water vapour condensing as the Earth cooled
• What two processes led to the reduction of carbon dioxide in the atmosphere before life on Earth?

  Carbon dioxide both dissolving in the oceans and some also then precipitating out producing sediments
• What caused the increase of oxygen in the Earth's atmosphere?

  Plants and algae producing oxygen through photosynthesis
• What is the word equation for photosynthesis?

  Carbon dioxide + water à glucose + oxygen ('light' should be written above the arrow)
• What is the symbol equation for photosynthesis?

  6CO2 + 6O2 → C6H12O6 + 6O2
• When did algae first start to produce oxygen on Earth?

  2.7 billion year ago
• When life evolved on Earth what three processes began to reduce the level of carbon dioxide in the atmosphere?

  Photosynthesis by plants and algae, formation of fossil fuels from carbon and the formation of sedimentary rocks
• Describe the formation of coal


  Formed from trees in dense forests in low-lying wetland areas. Flooding caused the wood from these forests to be buried in a way that prevented oxidation taking place. Compression and heating over millions of years turned the wood into coal.
• Describe the formation of crude oil and natural gas

  Formed from dead simple plants and tiny animals living in oceans and lakes that were buried under sediments. Lack of oxygen prevented oxidation from occurring and over millions of years, heat and pressure turned the remains of the organisms into crude oil and natural gas.
• What is the role of greenhouse gases in the atmosphere?

  To maintain temperature on Earth high enough to support life
• Name three greenhouse gases

  Water vapour, carbon dioxide and methane
• Describe how greenhouse gases warm the atmosphere

  They absorb heat radiated from the Earth and then release energy in all directions
• Describe how the Earth absorbs and emits electromagnetic radiation

  Short wavelength electromagnetic radiation from the Sun passes through the Earth's atmosphere and the earth absorbs most of the radiation and warms up. The earth then radiates longer wavelength infrared radiation into the atmosphere and space
• Which two greenhouse gases has human activity increased?

  Carbon dioxide and methane
• Name two human activities that have increased the level of carbon dioxide in the atmosphere

  Combustion of fossil fuels adding carbon dioxide and deforestation reducing the removal of carbon dioxide by photosynthesis
• Name two human activities that have increased the level of methane in the atmosphere

  Increased farming of cattle and farming rice in paddy fields both release methaneSee an expert-written answer!We have an expert-written solution to this problem!
• Why do most scientists believe that human activity will cause the temperature of the Earth's atmosphere to increase at the surface?

  The majority of evidence has been made available to all scientists and has been peer-reviewed by recognised journals
• What is the difficulty in modelling the effect of the changes in the Earth's atmosphere?

  The atmosphere is a complex system and we can only use simplified models
• What is the problem with opinions voiced on the climate change?

  Based on simple models, speculation, only part of the evidence and there are issues with bias
• What is the major cause of climate change?

  An increase in average global temperature
• Name four effects of global climate change

  Glaciers and ice-caps melting, sea levels rising, patterns of flood and drought changing, habitats changing
• What is a carbon footprint?

  The total amount of carbon dioxide and other greenhouse gases emitted over the life cycle of a produce, service or event
• How can you reduce a carbon footprint?

  By reducing the emissions of carbon dioxide and methane
• Describe actions to reduce a carbon footprint

  To reduce methane emissions, eat less beef; to reduce carbon dioxide emissions, switch to electricity produced from renewable resources, reduce car usage, travel less on aeroplanes
• Name the five pollutant gases released into the atmosphere when fuels are burnt

  Carbon dioxide, water vapour, carbon monoxide, sulfur dioxide and oxides of nitrogen
• Name two other non-gaseous pollutant from burning fuels

  Solid particle (soot) and unburned hydrocarbons that form particulates in the atmosphere
• How are carbon monoxide and carbon particles (soot) produced during the burning of fuels?

  By incomplete combustion
• How are oxides of nitrogen produced during the burning of fuels?

  The high temperature in a car engine is high enough for nitrogen to react with oxygen
• How is sulfur dioxide produced during the burning of fuels?

  By sulfur present in some fuels reacting with oxygen during combustion
• What are the hazards associated with carbon monoxide?

  Carbon monoxide is a toxic gas and as it is a colourless, odourless gas it is not easily detected
• What are the hazards associated with sulfur dioxide and oxides of nitrogen?

  Sulfur dioxide and oxides of nitrogen cause respiratory problems and acid rain
• How does sulfur dioxide and oxides of nitrogen cause acid rain?

  The gases dissolve in rain water
• What are the hazards associated with particulates in the atmosphere?

  Particulates cause global dimming and health problems in humans