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Chemistry C1
The early atmosphere
Scientists think that the early atmosphere was very much different to our atmosphere today and that evolution
caused this change in atmosphere. Scientists also thought that volcanoes have a large effect on what gases go
into the atmosphere and a long time ago. Scientists think that gases such as methane, carbon dioxide, ammonia,
nitrogen and water vapour were some of the gases present in the Earth's early atmosphere. This is because there
were many volcanoes during the time which released these gases hence scientists used this data to come to
theory as to which gases were present in the early atmosphere.
Scientists also believe that the Earth's early atmosphere was that of like Titan's which has an icy interior but
however has an atmosphere which contains 98% nitrogen this links in with the fact that the Earths early
atmosphere also contained so much nitrogen. On the other hand Mars and Venus have a lot of Carbon dioxide in
their atmosphere but also have many volcanoes on the surface; so the dilemma is how earth came to have so
much nitrogen.
Oxygen- scientists think that there was little or no oxygen in the early atmosphere this is because iron
compounds found In the Earths earliest rocks couldn't have formed in the presence of oxygen so there had to
be no or little oxygen in the atmosphere as well as the fact that volcanoes do not release oxygen.
How oceans were formed;
After oceans had developed the carbon dioxide in the atmosphere then dissolved in the oceans, scientists think
this is the way half of the CO2 was lost from the atmosphere. Various creatures such as molluscs and fish used
this carbon dioxide that was dissolved to make calcium carbonate shells, these creatures died and their shells fell
and became sediment and their sediment layered to become sedimentary rock and Limestone.
As well as this another process that scientists think contribute to the changing atmosphere is photosynthesis.
About 1 billion years ago organisms that could photosynthesise evolved these creatures came to evolve due to
the fact that organisms that could originally photosynthesise but were scarce began to develop and more and
more organisms began to photosynthesise. The rate at which carbon dioxide was being removed from the
atmosphere was the rate at which oxygen was being added. If the number of photosynthesising organisms
increase the amount of photosynthesis would increase as well thus we could reach the conclusion that as
photosynthesising organism's evolved carbon dioxide was being removed from the atmosphere this contributes
to the extremely low amounts of carbon dioxide gas in the atmosphere now.
Gases in the atmosphere now

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There are 3 main gases in the atmosphere, one being nitrogen- the most abundant and second being oxygen and
thirdly noble gases like argon. There are also traces of other gases in the atmosphere including sulphur dioxide,
carbon monoxide also water vapour is present in the atmosphere but as its amount is continuously changing we
do not include it in the composition of gases in the earth's atmosphere.
Nitrogen 78%
Oxygen 21%
Argon 0.9%
Carbon 0.…read more

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Metamorphic rock
Metamorphic rock can form when let's say heat and pressure is exerted onto limestone, this causes new crystals
to form which in this case is marble. When heated limestone's weakly joined grains become new crystals of CaCo3
which tightly interlock hence marble is harder than chalk or limestone.
Sedimentary rocks erode easily because metamorphic and igneous rocks have tightly interlocking crystals than
sedimentary rocks hence are harder to erode.…read more

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Precipitation Reactions- these are reactions which involve two soluble compounds reacting create an insoluble
product for example silver nitrate and potassium bromide react to produce the insoluble potassium nitrate and
silver bromide.…read more

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The importance of chlorine
Sea water contains salt which is a compound of sodium chloride, using electrolysis which is the splitting of
compounds called electrolytes we can extract chlorine by the electrolysis of sea water. To test whether a gas is
chlorine use damp litmus paper, it will first turn red but then get bleached by the chlorine.…read more

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Oxidation and Reduction
Extracting metal is reduction this is when we reduce the metal oxide into just a metal so taking away the oxygen.
When metals corrode they react with oxygen hence are being oxidised when iron rusts this is an example of
oxidation. Aluminium doesn't corrode as easily because it produces a protective layer of aluminium oxide to stop
further corrosion.…read more

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