chemistry of the atmosphere - roytoncrompton.e-act.org.uk · chemistry of the atmosphere aqa 2016...
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Chemistry of the Atmosphere
AQA 2016 Chemistry topic 9
9.1 The Composition and Evolution of the Atmosphere
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26/03/2020The Earth’s Atmosphere
Carbon dioxide, water vapour Oxygen Nitrogen Noble gases
For the last 200 million years the atmosphere has remained roughly the same – it contains 78% nitrogen, 21% oxygen, 1% noble gases and about 0.03% CO2
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4 Billion years 3 Billion years 2 Billion years 1 Billion years Present day
Evolution of the Earth’s AtmosphereCarbon
dioxide
Methane Ammonia Oxygen Nitrogen Others
The early atmosphere was like the present-day atmosphere of Venus or Mars
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4 Billion years 3 Billion years 2 Billion years 1 Billion years Present day
Evolution of the Earth’s AtmosphereVolcanic activity releases nitrogen, CO2, methane, ammonia and water vapour into the atmosphere. The water vapour condenses to form oceans.
Evidence for the early atmosphere is limited. Why is that?
Carbon from CO2 becomes locked up in sedimentary rocks as carbonates and fossil fuels. As the oceans form by condensing water vapour the carbonates and fossil fuels become locked underground, decreasing the amount of CO2.
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Changes in Oxygen and CO226/03/2020
4 Billion years 3 Billion years 2 Billion years 1 Billion years Present day
Carbon dioxide + water glucose + oxygen
6CO2 + 6H20 C6H12O6 + 6O2
Sunlight
Chlorophyll
Sunlight
Chlorophyll
Q. What are the equations for photosynthesis?
Somewhere around 2.7 billion years ago, algae and plants arrived and started taking in carbon dioxide and producing oxygen. A billion years later, there was enough oxygen for animals to evolve.
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Decreasing Carbon DioxideAs well as photosynthesis by plants and algae, atmospheric carbon dioxide levels were also decreased by the formation of carbonate rocks, e.g.:
ChalkLimestone
Marble (made from chalk or limestone)
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Formation of oil and gas
1) Layers of dead sea _____ settle on the seabed.
2) Layers of __________ rock build up on top.
3) The heat and ________ from these rocks, along with the absence of ______, mean that oil and gas are formed over ______ of years.
Words – sedimentary, millions, oxygen, creatures, pressure
9.2 Carbon Dioxide and Methane as Greenhouse Gases
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26/03/2020Carbon Dioxide and Global Warming
Global levels of Carbon Dioxide in PPM
Is there a link?
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The Greenhouse Effect1) Heat and light energy reach us from the sun (higher wavelengths such as visible light)…
2) …a lot of this heat is reflected off the Earth’s surface as lower wavelength infra red…
3) …some of the heat escapes back into space…
4) …while some of it is reflected back to the Earth by a layer of greenhouse gases (water vapour, CO2
and methane) – this is called The Greenhouse Effect
What problems do these next pictures show?
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26/03/2020Humans Causing Greenhouse Gases
How do the following activities affect the amount of greenhouse gases in the atmosphere?
1) Excessive burning of fossil fuels…
2)Large scale deforestation…
3) Large scale cattle farming
26/03/2020Carbon Dioxide and Global Warming
Global levels of Carbon Dioxide in PPM
Many scientists believe that
human activities will cause global
warming.
What reasons would people have for believing this?
What reasons would stop people believing global warming is happening?
Effects of Global Climate Change26/03/2020
What possible effects of climate change do these pictures show?
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Carbon Footprint26/03/2020
The “carbon footprint” is defined as the total amount of carbon dioxide and other greenhouse gases emitted over the full cycle of a product or event.
1) Drill for crude oil2) Put the oil through fractional
distillation3) Crack alkanes to make ethene4) Use heat to polymerise ethene5) Transport plastic bags to shops6) Transport bags to landfill sites
Steps in the bag’s life cycle
1) Use recycled materials2) Reduce consumption of the bags3) Manufacture them closer to
shops4) Recycle the bags after use
Ways to reduce the footprint
Q. Consider the humble plastic bag. What steps are involved in its life cycle and how can the carbon footprint of each step be reduced?
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Other ways to reduce the footprintHere are some other ways to reduce the carbon footprint:
Offset with renewable energy
Increase recycling
Personal choice
Carbon capture
Use better insulation
What factors might limit these options?
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9.3 Common Atmospheric Pollutants and their Sources
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PollutionSome examples of pollution…
Carbon dioxide, water vapour, carbon monoxide are caused by the burning of ____ _____. Carbon monoxide is a ____ gas and is not easily detected due to being ________.
Sulfur dioxide and nitrogen dioxide cause ____ ____ which damages trees and buildings and _________ problems in humans.
Particulates (unburned _______) can make buildings dirty and worsen breathing difficulties and cause global ______.
Words – hydrocarbons, dimming, fossil fuels, odourless, acid rain, respiratory, toxic
26/03/2020Combustion of Fuels
Lots of oxygen:
Some oxygen:
C
H
H
H
HO
O
OO
OH H
OH H
CO
O
Methane Oxygen+ Water+Carbon dioxide
Oxygen+
OO
OO
OO
Methane
C
H
H
H
H
C
H
H
H
H
Carbon monoxide
CO
CO
Water+
OH H
OH H
OH H
OH H
26/03/2020Other products of burning fuelsSulphur dioxide:
Nitrogen monoxide:
Nitrogen dioxide:
SO
O
Sulphur dioxide
SO
O
Sulphur Oxygen+
Nitrogen monoxide
NO
NO
Oxygen+
OO
Nitrogen
NN
OO
Oxygen+Nitrogen monoxide
NO
NO
Nitrogen dioxide
N OO
N OO
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Incomplete CombustionAs well as producing carbon monoxide, incomplete combustion can also produce soot:
Little oxygen:
CC
H
H
H
H
Methane
OO
Oxygen+
OH H
OH H
Water+Carbon
“Soot”
• 4 marks
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