chemistry of the atmosphere (the evolution of the atmosphere (phase 1 -…
chemistry of the atmosphere
the evolution of the atmosphere
phase 1 - volcanoes give out gases
first billion years of Earth's history, the surface was covered in
volcanoes that erupted & released lots of gases
- thought to be how early atmosphere was formed.
early atmosphere probably
mostly carbon dioxide
& no oxygen - like atmospheres of Venus & Mars
volcanic activity released nitrogen which built up in the atmosphere over time, & water vapour & small amounts of methane & ammonia.
phase 2: oceans, algae & green plants absorbed CO2
water vapour in the atmosphere condensed to form oceans.
lots of CO2 was removed from early atmosphere as it dissolved in the oceans. the dissolved CO2 went through a series of reactions to form carbonate precipitates that formed sediments on the seabed.
green plants & algae evolved & absorbed some of the CO2 to carry out photosynthesis.
:arrow_right_hook: marine animals evolved later & their shells & skeletons contained carbonates from the oceans.
some of the carbon these organisms took in from the atmosphere & oceans became locked up in rocks & fossil fuels after the organisms died.
when plants, plankton & marine animals die, they fall to the seabed & get buried in layers of sediment --> over millions of years, they become compressed & form sedimentary rocks, oil & gas - trapping the carbon within them & helping to keep CO2 levels in the atmosphere reduced.
coal, crude oil & natural gas made through this process - 'fossil fuels'.
crude oil & natural gas 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 a sedimentary rock mostly made of calcium carbonate deposits from the shells & skeletons of marine organisms.
phase 3: green plants & algae produced oxygen.
green plants & algae absorbed CO2 & produced oxygen by photosynthesis.
algae evolved first (2.7bn years ago) then over the next billion years, plants evolved.
as oxygen levels built up in the atmosphere, more complex life could evolve.
about 200 million years ago, the atmosphere reached a composition similar to what it is today: approximately 80% nitrogen, 20% oxygen & small amounts of other gases: CO2, noble gases & water vapour.
greenhouse gases & climate change
greenhouse gases like CO2, methane & water vapour act like an insulating layer in the Earth's atmosphere - allows Earth to be warm enough to support life.
all particles absorb certain frequencies of
- greenhouse gases don't absorb the incoming short wavelength radiation from the sun but do absorb the long wavelength radiation that gets reflected back off the Earth.
they re-radiate it in all directions, including back towards the Earth --> the long wavelength radiation is thermal radiation so results in warming the surface of the Earth - the
human activity affects the amount of greenhouse gases in the atmosphere:
deforestation: fewer trees means less CO2 is removed from the atmosphere via photosynthesis.
burning fossil fuels: carbon that was 'locked up' in these fuels is released as CO2.
agriculture: more farm animals produce more methane through their digestive processes.
creating waste: more landfill sites & more waste from agriculture means more CO2 & methane released by decomposition of waste.
increasing carbon dioxide is linked to climate change
varies naturally but the average temp. of Earth's surface has been
recently - most scientists agree that the extra CO2 from
is causing this increase & that this will lead to climate change.
evidence for this has been peer-reviewed so the info. is reliable.
it is hard to fully understand the Earth's climate as it is so
& there are so many variables so it is hard to make a model that isn't over-simplified.
this has led to
, particularly in the
where stories may be biased or give only some of the information.
climate change could have
so it is important to make predictions so that policy-makers can make decisions now:
an increase in global temperature could lead to polar ice caps melting, causing a rise in sea levels, increased flooding in coastal areas & coastal erosion.
changes in rainfall patterns (amount, timing & distribution) may cause some regions to get too much or too little water &, along with changes in temperature, may affect the ability of certain regions to produce food.
the frequency & severity of storms may increase.
changes in temperature & the amount of water available in a habitat may affect wild species, leading to differences in their distribution.
carbon footprints are a
measure of the amount of carbon dioxide & other greenhouse gases released over the full life cycle of something
- can be a service, an event, a product etc.
measuring the total carbon footprint can be difficult or even impossible as there are so many different factors to consider e.g. would have to count the emissions released as a result of sourcing all the parts of a product, making it, & the emissions produced when it is used & when it is disposed.
a rough calculation can give a good idea of what the worst emitters are so people can avoid them in the future.
reducing the amount of greenhouse gases released due to a process reduces its carbon footprint:
renewable energy sources or nuclear energy can be used instead of fossil fuels.
using more efficient processes could conserve energy & reduce waste - lots of waste decomposes to release methane so this would reduce methane emissions.
governments could tax companies or individuals based on the amount of greenhouse gases they emit e.g. taxing cars based on the amount of CO2 they emit over a set distance could mean that people choose to buy cars that are more fuel-efficient & so less polluting.
governments could put a cap on emissions of all greenhouse gases that companies make then sell licenses for emissions up to that cap (limit).
there is technology that captures the CO2 produced by burning fossil fuels before it is released into the atmosphere & can then be stored deep underground in cracks in the rock such as old oil wells.
actually cutting emissions is difficult as there is still a lot of work to be done on alternative technologies that result in lower CO2 emissions.
a lot of governments are worried that making these changes will impact on the economic growth of communities which could be bad for people's well-being & is important for countries that are still developing.
not everyone agrees with this so it is hard to make international agreements to reduce emissions - most countries don't want to sacrifice their economic development if they think that others won't do the same.
individuals in developed countries need to make changes to their lifestyles but it may be hard to to get people to make changes if they don't want to & if there isn't enough education provided about why the changes are necessary & how to make them.
fossil fuels (e.g. crude oil & coal) contain hydrocarbons & during combustion, the carbon & hydrogen in these compounds are oxidised so that CO2 & water vapour are released into the atmosphere.
when there is enough oxygen, all the fuel burns (complete combustion) but if there isn't enough oxygen & some of the fuel doesn't burn,
occurs :arrow_right: under these conditions, solid particles (
) of soot (carbon) & unburnt fuel are released & carbon monoxide can be produced as well as CO2.
particulates in the air cause problems:
if particulates are inhaled, they can get stuck in the lungs & cause damage which can lead to
they are bad for the environment - they or the clouds they help to produce, reflect sunlight back into space which means less light reaches the Earth, causing
carbon monoxide produced from incomplete combustion is bad too:
CO is dangerous as it can stop the blood from carrying oxygen around the body properly by binding to the haemoglobin in the blood that normally carries oxygen (O2) so
is able to be
around the body.
a lack of oxygen in the blood can lead to fainting, a coma or even death.
carbon monoxide is colourless & odourless so is difficult to detect, making it more dangerous.
(SO2) is released during the combustion of fossil fuels that contain sulfur impurities - the sulfur in the fuel becomes oxidised.
are created from the reaction between nitrogen & oxygen in the air, caused by the heat of the burning (can happen in the internal combustion engines of cars.)
when these gases mix with clouds, they form dilute sulfuric acid or dilute nitric acid which then falls as
acid rain kills plants & damages (limestone) buildings & statues & makes metal corrode.
sulfur dioxide & nitrogen oxides can be bad for human health as they cause respiratory problems if they are inhaled.
SO2 gas reacts with water to form sulfuric acid.
sulfur impurities can be tested for in a fuel by bubbling the gases from combustion through a solution containing Universal indicator.
if the fuel contains sulfur, the gases will contain SO2 which will form sulfuric acid & turn the indicator red.