Chemistry of the Atmosphere 23/04/2019 23/04/2019 Chemistry of the Atmosphere AQA 2016 Chemistry topic 9 W Richards The Weald School

9.1 The Composition and Evolution of the Atmosphere 23/04/2019 9.1 The Composition and Evolution of the Atmosphere

The Earth’s Atmosphere 23/04/2019 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 Carbon dioxide, water vapour Oxygen Nitrogen Noble gases

Evolution of the Earth’s Atmosphere 23/04/2019 Carbon dioxide Methane Ammonia Oxygen Nitrogen Others The early atmosphere was like the present-day atmosphere of Venus or Mars 4 Billion years 3 Billion years 2 Billion years 1 Billion years Present day

Evolution of the Earth’s Atmosphere 23/04/2019 Volcanic 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? 4 Billion years 3 Billion years 2 Billion years 1 Billion years Present day 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.

Changes in Oxygen and CO2 23/04/2019 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. 4 Billion years 3 Billion years 2 Billion years 1 Billion years Present day Q. What are the equations for photosynthesis? Carbon dioxide + water glucose + oxygen 6CO2 + 6H20 C6H12O6 + 6O2 Sunlight Chlorophyll

Decreasing Carbon Dioxide 23/04/2019 As well as photosynthesis by plants and algae, atmospheric carbon dioxide levels were also decreased by the formation of carbonate rocks, e.g.: Chalk Limestone Marble (made from chalk or limestone)

Formation of oil and gas 23/04/2019 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 23/04/2019 9.2 Carbon Dioxide and Methane as Greenhouse Gases

Carbon Dioxide and Global Warming 23/04/2019 Global levels of Carbon Dioxide in PPM Is there a link?

The Greenhouse Effect 23/04/2019 1) Heat and light energy reach us from the sun (higher wavelengths such as visible light)… 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 2) …a lot of this heat is reflected off the Earth’s surface as lower wavelength infra red…

What problems do these next pictures show? 23/04/2019 What problems do these next pictures show?

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Humans Causing Greenhouse Gases 23/04/2019 How do the following activities affect the amount of greenhouse gases in the atmosphere? Excessive burning of fossil fuels… Large scale deforestation… 3) Large scale cattle farming

Carbon Dioxide and Global Warming 23/04/2019 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 Change 23/04/2019 What possible effects of climate change do these pictures show?

Carbon Footprint 23/04/2019 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. 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? Steps in the bag’s life cycle Ways to reduce the footprint Drill for crude oil Put the oil through fractional distillation Crack alkanes to make ethene Use heat to polymerise ethene Transport plastic bags to shops Transport bags to landfill sites Use recycled materials Reduce consumption of the bags Manufacture them closer to shops Recycle the bags after use

Other ways to reduce the footprint 23/04/2019 Here are some other ways to reduce the carbon footprint: Use better insulation Offset with renewable energy Increase recycling What factors might limit these options? Carbon capture Personal choice

9.3 Common Atmospheric Pollutants and their Sources 23/04/2019 9.3 Common Atmospheric Pollutants and their Sources

Pollution Some examples of pollution… 23/04/2019 Some 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

Combustion of Fuels Lots of oxygen: Some oxygen: Methane Oxygen + 23/04/2019 C H O O H C O Lots of oxygen: Methane Oxygen + Carbon dioxide Water + Water + O H Methane C H Oxygen + O C O Some oxygen: Carbon monoxide

Other products of burning fuels 23/04/2019 S O Sulphur dioxide Sulphur dioxide: S O Sulphur Oxygen + Nitrogen monoxide N O Oxygen + O Nitrogen N Nitrogen monoxide: O Oxygen + Nitrogen monoxide N Nitrogen dioxide N O Nitrogen dioxide:

Incomplete Combustion 23/04/2019 As well as producing carbon monoxide, incomplete combustion can also produce soot: Little oxygen: C H Methane O Oxygen + Water Carbon “Soot”