Topic 9 - Chemistry of the Atmosphere Flashcards
How do fossil fuels release gases and particles into the atmosphere
-Fossil fuels such as crude oil and coal contain hydrocarbons and during combustion the hydrogen and carbon in these compounds are oxidised so carbon dioxide and water are released into the atmosphere
What is complete combustion
When there is plenty of oxygen so all fuel burns
What is incomplete combustion and what can it cause to be released
-When there’s not enough oxygen some fuel doesn’t burn and solid particles of carbon and unburnt fuel are released
-carbon monoxide can be produced as well as carbon dioxide
What problems can particles in the atmosphere cause
-If they are inhaled they can get stuck in the lungs and cause damage possibly leading to respiratory problems
-They’re bad for the environment as the particles or clouds they produce reflect sunlight back into space so less light reaches the Earth - causing global dimming
Why is carbon monoxide in the atmosphere a problem (3)
-It can stop your blood from doing its job of carrying oxygen around the body by binding to the haemoglobin in your blood that normally carries O2 so less oxygen can be transported around 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 making it very dangerous
How is sulphur dioxide released into the atmosphere
During the combustion of fossil fuels such as coal that contain sulphur impurities -the sulphur in the fuel becomes oxidised
How is nitrogen oxide created during combustion
From a reaction between the nitrogen and oxygen in the air caused by the heat of the burning
What are the negatives of sulphur dioxide and nitrogen oxides being released into the atmosphere
-They mix with clouds and form dilute sulfuric acid or dilute nitric acid which falls as acid rain
-Acid rain kills plants, damages buildings/statues. It also makes metal corrode.
-Sulphur dioxide and nitrogen oxide can also be bad for human health - they cause respiratory problems if breathed in
What is phase 1 of the evolution of the atmosphere
-The first billion years of Earth’s history had the surface covered in volcanoes which erupted and released lots of gases and this may have been how the early atmosphere was formed
-The early atmosphere was probably mostly carbon dioxide, with virtually no oxygen like Mars and Venus today
-It also released nitrogen which built up in the atmosphere over time. as well as water vapour and small amounts of methane ammonia
What is phase 2 of the evolution of the atmosphere
-When the water vapour in the atmosphere condensed it formed oceans
-Lots of CO2 was removed as it dissolved in the oceans. This dissolved CO2 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 CO2 so that they could carry out photosynthesis. Later, marine animals evolved. Their shells and skeletons contained carbonates from the oceans.
-Some of the CO2 of these organisms took in from the atmosphere and oceans became locked up in rocks and fossil fuels after the organisms
In the second phase of the evolution of the atmosphere what happened to plants, plankton and marine animals who died
-They fell 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 the carbon within them and helping to keep CO2 levels in the atmosphere reduced
-Fossil fuels (coal, crude oil and natural gas) are made by this processs
-Crude oil and natural gas are formed from deposits of plankton. These fossil fuels form reservoirs under the seabed when they get trapped in rocks
-Coal is a sedimentary rock made from thick plant deposits
-Limestone is also a sedimentary rock. It’s mostly made of calcium carbonate deposits from the shells and skeletons of marine organisms
What is phase 3 of the evolution of the atmosphere
-As well as absorbing CO2 in the atmosphere green plants/algae produce O2 by photosynthesis
-Algae evolved first about 2.7 billion years then over the next billions years or so green plants also allowed
-As oxygen levels built up in the atmosphere over time, more complex life could evolve
-Eventually about 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 (less than 1%), mainly CO2, noble gases and water vapour
What are greenhouse gases
Act like an insulating layer in the Earth’s atmosphere (e.g. CO2, methane and water vapour)
What is the greenhouse effect and how does it happen
-All particles absorb certain frequencies of radiation. Greenhouse gases don’t absorb the incoming short wavelength radiation from the sun -but they do absorb the long wavelength radiation that gets reflected back off the Earth. Then they re-radiate it in all directions. The long wave radiation is thermal radiation, so it results in warming of the surface of the Earth.
How does human activity affect the amount of greenhouse gases in the atmosphere
-Deforestation : fewer trees mean less CO2 removed from the atmosphere by photosynthesis
-Burning fossil fuels : carbon that’s was locked up in these fuels is released is released as CO2
-Agriculture : more farm animals produce more methane through their digestive processes
-Creating waste : more landfill sites and more waste from agriculture means more CO2 and methane released by decomposition
