Oxygen is the most
reactive gas in out
atmosphere.
Oxidation reactions
can be seen in
rusting metals.
The type of
iron
compounds
found in rocks
show a record
of oxygen
content at the
time the rock
was formed
recent rocks contain iron oxide, but
iron in older rocks is not oxidised.
This proves that the amount of
oxygen in our atmosphere has
increased.
Nitrogen levels have
increased and oxygen
levels have dramatically
decreased.
the evolution of life
caused major changes to
the gases in our
atmopshere
our atmosphere
has formed from
gases that escaped
from volcanoes
a long time ago, the main
gases in our atmosphere were
water vapour and carbon
dioxide
rocks contain a record
of gases present in the
atmosphere at the time
they formed
this allows scientists to
see how the
atmosphere has
changed
as the eart cooled, water vapour in
the atmosphere condensed and fell
as rain to create out oceans
the carbon dioxide in the
atmosphere at the time
dissolved into the water,
causing the percentage to
drop
early sea plants used
this carbon dioxide for
photosynthesis and
released oxygen into
the atmosphere,
causing percentages to
rise.
some sea animals took in
carbon dioxide to make
their shells. shells fromm
dead sea animals collected
on the floor of the oceans
and turned into carbonate
rocks
when water
condenses,
intermolecular
forces hold the
molecules
together = H20
photosynthesis decreased levels of co2 and increased levels of o2
6CO2 + 6H2O => C6H12O6 + 6O2
carbon dioxide + water => glucose + oxygen
+(energy)