chemistry of the atmosphere

• When did Earth form?

  4.6 billion years ago
• What gases were present when Earth formed?

  Water vapour, carbon dioxide, methane, ammonia
• Where did the gases present in early Earth's atmosphere come from?

  Volcanic activity
• Why can we not be certain what happened when Earth formed?

  Evidence is limited as it was over a long period of time and it was a long time ago
• How was the ocean formed?

  Water vapour condensed as Earth cooled down
• Why did levels of carbon dioxide start to reduce?

  Carbon dioxide dissolved in the oceans and made sediment on the sea bed
• What happened to the amounts of carbon dioxide and oxygen when land plants evolved and why?

  Amounts of carbon dioxide declined and amounts of oxygen built up because of photosynthesis from algae
• Photosynthesis equation


  Carbon dioxide + water -> glucose + oxygen
• Why did the amount of nitrogen increase?

  Increased volcanic activity, and oxygen reacting with ammonia to form more oxygen
• What is coal formed from?

  Thick plant deposits such as ancient plants and trees
• What is natural gas and crude oil made from?

  Deposits of plankton
• How do fossil fuels permanently remove carbon dioxide from the atmosphere?

  Carbon dioxide is trapped between oil and gas, which are buried in the absence of oxygen and are compressed under intense heat and pressure over millions of years.
• How is limestone rock formed?

  From calcium carbonate deposits from shells and skeletons of marine organisms
• In the present day atmosphere how much of each gas is present?

  Approx. 78% nitrogen, 21% oxygen and >1% of other gases, such as carbon dioxide (0.04%), water vapour and argon.
• Types of combustion

  Incomplete and complete
• Complete combustion


  When fuels burn completely because there is lots of oxygen available. The products of complete combustion are carbon dioxide and oxygen.
• Incomplete combustion


  When a fuel does not burn fully because there is a limited supply of oxygen. The products of incomplete combustion are either carbon monoxide + water or carbon soot (or carbon particulates) + water
• Pollutants produced by combustion

  Carbon dioxide, carbon monoxide, carbon particulates, sulfur dioxide, nitrogen oxides
• Carbon dioxide is produced by complete combustion and is a greenhouse gas.
• What can we do about carbon dioxide?

  Reduce carbon footprint, use renewable energy resources.
• Carbon monoxide is produced by incomplete combustion and is a toxic gas that binds to haemoglobin to prevent oxygen from binding.
• What can we do about carbon monoxide?

  Use catalytic converters
• Carbon particulates are produced by incomplete combustion and cause global dimming.
• What can we do about carbon particulates?

  Use filters in exhausts
• Sulfur dioxide is produced when sulfur impurities in fossil fuels react with oxygen when burnt and cause acid rain
• What can we do about sulfur dioxide?

  Flue gas desulfurisation (using CaO to neutralise sulfur dioxide) or remove sulfur impurities before burning.
• Nitrogen oxides are produced when oxygen and nitrogen from the air react at high temperatures and cause acid rain and exacerbates asthma.
• What can we do about nitrogen oxides?

  Use catalytic converters
• What do catalytic converters do?

  They convert carbon monoxide and nitrogen oxides to carbon dioxide and nitrogen
• The Greenhouse Effect

  The sun emits short wavelength radiation which passes through the layer of greenhouse gases in the atmosphere. It is absorbed by the Earth's surface and then re-emitted as long wavelength radiation, which is absorbed by greenhouse gases such as water vapour, methane and carbon dioxide. This increases the average global temperature.
• What are the greenhouse gases?

  Carbon dioxide, methane, water vapour
• Greenhouse gases in the atmosphere maintain temperatures on Earth high enough to support life.
• What activities lead to an increase in carbon dioxide?

  Deforestation, increased burning of fossil fuels
• What activities lead to an increase in methane?

  Increased cattle farming, increased waste decomposition.
• Four possible effects of climate change include: melting ice, rising sea levels, flooding and extremes of weather.
• Carbon footprint


  A measure of the total amount of greenhouse gases, such as carbon dioxide, released over a full life cycle of a product, service or event.
• How can you reduce your carbon footprint?

  Using renewable energy resources, walking or cycling more often than using a car.
• Why may someone not be able to reduce their carbon footprint?

  It might be too expensive to switch to an electric car or fit solar panels on your roof, you might live too far away to cycle to work.