1. Atmospheric Chemistry
Done by: Soh Zheng Yang
Class: 3B118

2. Agenda
• Introduction
• Composition
• Pollutants
• Acid Rain
• Global Warming
• Ways to prevent Global Warming

3. Introduction
• Many effects on earth, such as global warming , are
brought by chemical reactions.
• The Earth is surrounded by a think air layer called the
atmosphere. Air is essential for life. Without air, life
would not be possible.

4. Composition
Atmosphere composition…
• Nitrogen 78.084%
• Oxygen 20.946%
• Argon 0.934%
• Other gases >1%
Atmospheric chemistry allows us to understand the
changes of atmosphere composition and gives us views on
the air pollution, thus making us to protect the earth……

5. Pollutants
Pollutants can come from both natural sources and from human
activities. However, human are usually the main cause of the
atmospheric problems as 80% of the world-wide energy demand
is currently supplied by the fossil fuels coal, oil or gas.
6 main pollutants: Natural Sources:
• Sulfur dioxide - Volcanic eruptions
• Nitrogen oxides - Forest fires
• Carbon monoxide - Biological processes
• Methane
• Unburnt hydrocarbons
• Ozone

6. Sulfur Dioxide
• Petroleum and Coal are used as fuels to generate energy.
• However, large amount fossil fuels are burnt in industries to
provide energy.
• Both these fuels contain sulfur as an impurity.
When these fuels are burnt, the sulfur is oxidized to form
sulfur dioxide.
S(s) + O2(g)  SO2 (g)
(present (present
in fuel) in air)

7. Nitrogen Oxides
• At high temperatures, nitrogen and oxygen in the air
combine to form nitrogen monoxide.
• The nitrogen monoxide combines with more oxygen
molecules in the atmosphere to become nitrogen dioxide.
• Occurs Naturally in lighting and forest fires
• Most produced inside vehicle engines and Incinerators.
N2 (g) + O2 (g)  2NO (g)
2NO (g) + O2 (g)  2NO2 (g)

8. Carbon Monoxide
• Carbon Monoxide is a colorless, odorless, and tasteless gas.
• Mostly comes from incomplete combustion of fuel in engines.
• Highly toxic to humans and animals in higher quantities.
• It combines with hemoglobin in the red blood cells to produce
carboxyhemoglobin in normal persons.
• It is especially dangerous because it is colourless and
odourless, without any warning of its presence.
Video on the effects:
http://www.youtube.com/watch?v=wKIrbq2pWvw

9. Methane
• Methane is a colorless, odorless gas.
• Naturally present in the atmosphere from the bacterial
decay of vegetation and other sources.(Small amount)
• Increasing amount because of human activities.
• Methane is a relatively potent greenhouse gas, trapping the
heat in the atmosphere causing Global warming.

10. Unburnt Hydrocarbons
• Produce when incomplete combustion of
octane in petrol.
• hydrocarbons emitted after petroleum is
burned in an engine

11. Ozone
• Form of Oxygen; Colourless gas.
• Ozone layer in the upper atmosphere Surrounds the Earth
at high altitudes and prevents us from harmful solar
radiation.
However......
• An air pollutant at the lower atmosphere with harmful
effects on the respiratory systems of animals and burning
sensitive plants.
Next page……

12. Ozone Hole
• A portion of the layer is depleted by
chlorofluorocarbons(CFCs)
• Although CFCs are harmless, they can rise up high into the
atmosphere and decomposed by sunlight to produce
chlorine atoms.
• The chlorine atoms react with the ozone molecules and
destroy them by converting them into oxygen molecules.

13. Photochemical Smog
• Caused by reactions between
sunlight and pollutants.
• Often invisible, it can be extremely
harmful, leading to irritations of the
respiratory tract and eyes.

14. Acid Rain
• Formed from 2 air pollutants – sulfur dioxide and
nitrogen dioxide.
• Sulfur dioxide and nitrogen dioxide reacts with oxygen
and water to form sulfuric acid and nitric acid
respectively which dissolves in rainwater, making it
acidic.
2SO2 (g) + O2(g) + 2H2O (l)  SO2 (g)

15. Effects of Acid Rain
• Causes soils to become acidic, plants do not grow well.
• Cause water to become acidic which results in the many
deaths of marine life.
• Corrodes buildings made of limestone or cement as they
react with calcium carbonate.

16. Global Warming
• Increasing volume of atmospheric Methane and Carbon
dioxide.
• Trap the heat radiation and prevent it from entering the
space.
• Due to human activities, this greenhouse gases" is
occupying more percentage in the total composition of air.
• Resulting the Earth to become hotter.

17. Consequences of Global Warming
• The polar ice caps will melt.
• Seawater will expand and sea levels will rise, causing
frequent flooding of low-lying areas.
• Aquatic animals’ habitats will be greatly affected, causing
animals like polar bears to become extinct.

18. Preventing Global Warming
• Reducing the amount of fossil fuels burned by using solar
panels.
• More electricity could be generated through other means
such as wind, tidal, hydroelectric power.
• Say “No” to Global Warming

19. References
• http://www.wisegeek.com/what-is-photochemical-smog.htm
• http://www.google.com.sg/imghp?hl=en&tab=ii
• http://en.wikipedia.org/wiki/Atmospheric_methane

20. • The End~