Topic 9- Chemistry of the amotmosphere

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  • Created by: millieray
  • Created on: 19-03-18 16:31

The Evolution of the Atmosphere- Phase 1

  • The first billion years of earth's history the surface was covered in volcanoes that erupted and released lots of gases. We think this was how the early atmosphere was formed.
  • The early atmosphere was mostly carbon dioxide, with virtually no oxygen, quite like the atmosphere of mars and venus today.
  • Volcanic activity also released nitrogen, which built up in the atmosphere over time, as well as water vapour and small amounts of methane and ammonia.
  • As the earth cooled the water vapour in the atmosphere condensed, forming the oceans.
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The Evolution of the Atmosphere- Phase 2

  • When the water vapour in teh atmosphere condensed it formed the oceans.
  • Lots of carbin dioxide was removed from the early atmosphere as it dissolved in the oceans. This dissolved carbon dioxide then went through a series of reactions to form carbonate precipitates that formed sediments on the seabed.
  • Green plants and algae evolved and absorbed some of the carbon dioxide so that they could carry out photosynthesis.
  • Later, marine animals evolved. Their shells and skeletons contained carbonates from the oceans.
  • Some of the carbon these organisms took in from the atmosphere and oceans came locked up in rocks and fossil fuels after organisms died.
    • When plants, plankton and marine animals die, they fall to the seabed and get buried by layers of sediment. Over millions of years, they become compressed and form sedimentary rocks, oil and gas- trapping carbon within them and helping to keep carbon dioxide levels in the atmosphere reduced.
    • Things like coal, crude oil and natural gas that are made by this process are called fossil fuels.
    • Crude oil and natural gas are fromed from deposits of plankton. These fossil fuels form reservoirs under the seabed when they get trapped in rocks.
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Phase 2 continued

  • Coal is a sedimentary rock made from thick plant deposits.
  • Limestone is also a sedimentary rock. It's mostly made of calcium carbonate deposits form the shells and skeletons of marine organisms.
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The Evolution of the Atmosphere- Phase 3

  • As well as absorbing carbon dioxide from the atmosphere, green plants and algae produced oxygen by photosynthesis: carbon dioxide + water ----> glucose + oxygen
  • Algae evolved first - about 2.7 billion years ago. then over the next billion years, green plants also evolved.
  • As oxygen levels built up in the atmosphere over time, more complex life could evolve.
  • Eventually, approximately 200 million years ago, the atmosphere reached a composition similar to what it is today: 80% nitrogen, 20% oxygen and small amounts of other gases (mainly carbon dioxide, noble gases and water vapour)
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Greenhouse Gases and Climate Change

  • Greenhouses gases like carbon dioxide, methane and water vapoiur act like an insulating layer in the earth's atmosphere - this amongst other factors, allows the earth to be warm enough to support life.
  • All particles absorb certain frequencies of radiation.
  • Greenhouse gases don't absorb the incoming short wavelngth radiation from the sun but do absorb the long wavelength radiation that gets reflected off by the earth. They then re-radiate it in all directions- including back towards earth. This is the greenhouse effect.
  • Human activities that increase the number of greenhouse gases in the atmosphere include:
    • Deforestaton
    • Burning fossil fuels
    • Agriculture: mroe farm animals produce more methane through their digestive processes.
    • creating waste: more landfill sites and more waste from agriculture means more carbon dioxide and methane released by decomposition from waste.
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The greenhouse effect

Image result for greenhouse effect

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Carbon Dioxides Link To Climate Change

  • Recently the average temeperature of the Earth's surface has been increasing.
  • Most scientists agree that the extra carbon dioxide from human activity is causing this increase and that this will lead to climate change.
  • Evidence for this has been peer-reviewed making the information reliable.
  • It's hard to fully understand the Earth's climate because it's so complex, and there are so many variables, that it's very hard to make a model that isn't oversimplified.
  • This has led to specualtion in the media - where stories may be biased or only partial information given.
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Climate Changes Dangerous Consequences

  • It’s important to make predictions about the consequences of climate changes that policy makers can make decisions now. For example:
    • An increase in global temperatures could lead to the melting of polar ice caps - causing sea levels to rise and increasing flooding and erosion in coastal areas.
    • Changes in rainfall patterns may cause some regions to get too much or too little water. This along with changes in temperatures could mean certain regions are unable to produce food.
    • The frequency and severity of storms could increase.
    • The distribution of wildlife may change as a result of temperature and water patterns changing.
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Carbon Footprint

  • They are a measure of the amount of carbon dioxide and other greenhouse gases released over the full life cycle of something. This can be an event, a service, a product, almost anything.
  • However measuring a carbon footprint can be very difficult because there’s so many different factors to consider. For example, you would have to count the emissions released as a result of sourcing all the parts of your product and the emissions produced when using the product and disposing it.
  • But, a rough calculation can give a good idea of what the worse emitters are- so that people can avoid them in the future.
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Ways To Reduce Carbon Footprints

  • Anything that reduces the amount of greenhouse gases given out by a process will also reduce its carbon footprint.
  • Somethings that can be done are:
    • Renewable energy sources or nuclear energy can be used as a replacement for fossil fuels.
    • Using more efficient processes could conserve energy and cut waste. Lots of waste decomposes to release methane, so this will reduce methane emissions.
    • Governments could tax companies or individuals based on the amount of greenhouse gases they emit- e.g. taxing cars based on the amount of carbon dioxide they emit over a set distance. This could mean people choose to buy ones that are more fuel efficient.
    • Governments can also put a cap on emissions of all greenhouse gases that companies make.
    • There’s also technology that captures the carbon dioxide produced by burning fossil fuels before it’s released into the atmosphere- it can then be stored underground in cracks in the rock such as old oil wells.
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The Reality Of Reduction

  • For a start, there’s still a lot of work to be done on alternative technologies that result in lower carbon dioxide emissions.
  • A lot of governments are also worried that making these changes will impact on the economic growth of communities. This is particularly important in developing countries.
  • Not everyone is on board, it’s hard to make international agreements to reduce emissions. Most countries don’t want to sacrifice their economic development if they think that others won’t do the same.
  • Individuals in developed countries need to make changes to their lifestyles. But it might be hard to get people to make changes if they don’t want to and if there isn’t enough education provided about the ways to reduce carbon emissions.
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Air Pollution

  • Fossil fuels, such as crude oil and coal, contain hydrocarbons. During combustion, the carbon and hydrogen in these compounds are oxidised so that carbon dioxide and water vapour are released into the atmosphere.
  • When there’s plenty of oxygen, all the fuel burns- this is called complete combustion.
    If there’s not enough oxygen, some of the fuel doesn’t burn - this is called incomplete combustion. Under these conditions, solid particles ( called particulates) of soot and unburnt fuel are released and carbon monoxide can be produced as well as carbon dioxide.
  • Particulates in the air can cause all sorts of problems:
    • If particulates are inhaled, they can get stuck in the lungs and cause damage. This can then lead to respiratory problems.They’re also bad for the environment- they themselves, or clouds they help to produce, reflect sunlight back into space. This means that less light reaches earth causing global dimming.
  • Carbon Monoxide is also a product of combustion:
    • Carbon monoxide is really dangerous because it can stop your blood from carrying oxygen around the body. It does this by binding to the haemoglobin in your blood that normally carries oxygen- so less oxygen is able to be transported round your body.A lack of oxygen in the blood can lead to fainting, a coma or even death.
    • Carbon monoxide doesn’t have any colour or smell, so it’s very hard to detect. This makes it even more dangerous.
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Sulfur Dioxide And Oxides of Nitrogen

  • Sulfur dioxide is released during the combustion of fossil fuels, such as coal, that contain sulfur impurities - the sulfur in the fuel becomes oxidised.
  • Nitrogen oxides are created from a reaction between the nitrogen and oxygen in the air, caused by the heat of the burning.
  • When these gases mix with clouds they form dilute sulfuric acid or dilute nitric acid. This then falls as acid rain.
  • Acid rain kills plants and damages buildings and statues. It also makes metal corrode.
  • Sulfur dioxide and nitrogen oxides can also be bad for human health in the form of respiratory problems if you breathe them in.
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