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تاريخ التسجيل : 11/05/2015
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IRON OXIDATION

في الأحد مايو 17, 2015 5:18 pm
IRON OXIDATION
[size=15]Scientists cannot directly sample Earth’s atmosphere from billions
of years ago. Instead, they look for clues about the past makeup of
the atmosphere. Some of these clues are in the chemistry of rocks.
These rocks formed in ancient marine environments. Iron oxide is one
compound in these rocks. It tells a lot about the amount of oxygen in
Earth’s ancient atmosphere.
In the Investigate, you dissolved an iron tablet in a beaker of tap water.
You most likely observed the water change to reddish brown as the iron
tablet dissolved. Gradually, reddish-brown particles formed in the water.
This gave it a cloudy appearance. As the particles grew in size, they sank
down to the bottom of the beaker. Over time, more and more particles
accumulated on the bottom of the beaker. The next day, the reddish
brown disappeared and the water was clear.
The change in color you observed
is due to the chemical process
called oxidation. Oxidation is the
combination of a substance with
oxygen. In the Investigate, iron
oxidized, or combined with oxygen,
to form iron oxide. This reaction
takes place when both elements
are dissolved in water. The iron
came from the tablet. The oxygen
dissolved in the water came from the
atmosphere. As more iron combined
with oxygen, larger and larger ironoxide particles formed. They sank
to the bottom of the container.
This removed the iron from the
solution. If you do not add new
iron, the concentration of iron in
the solution decreases.
You have most likely had other
experiences with iron oxidation.
Iron is found in many materials that
are used daily. For example, iron is
found in cars, bicycles, ships, nails,
and support beams for buildings.
Paint or rust proofing is used to
protect the iron in these items from
rusting. They prevent the iron from
coming into contact with moisture
and oxygen. This prevents iron oxide
from forming
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