Chemistry Project~
By 3B TSUI MAN HUNG (29)
WONG CHI WO (32)
Content
P.1
Profile of our work
P.2
Composition of sea water
P.3-7
Details about sodium chloride
P.8-9
Electrolysis of sea water
P.10
Uses of products
P.11
Conclusion
Profile of our work
For our project, first of all we will talk about the
composition of sea water.Then we will detach to two
parts: In the first part is going to tell you some details
about the main salt of sea water~sodium chloride.
After that, we will also tell you about the electrolysis
of sea water and uses of products. We hope you may
enjoy it!
Composition of sea water
Salt composition of sea water
calcium
chloride
sodium 3%
sulphate
11%
other salts
3%
magnesium
chloride
15%
sodium
chloride
68.0%
Sea water is made up
by water and salts, so it is
very salty, and it contains
many types of salts. Sea
water is a solution, there is
35g of dissolved
substances in 1000g of sea
water.The main one is
common salt (sodium
chloride), which are used
in kitchens.
Sodium chloride (common salt)
In last page, we can see that there are 68% of
sodium chloride in sea water. We can take some pure
sodium chloride by filtration or crystallization. Pure
sodium chloride consists of sodium ions and chloride
ions. But how can we test about them? Please go on to
see the following pages.
How can we take the pure sodium chloride?
Ⅰ. Filtration
1.
Pour sea water onto the
folded filter paper in a
filter funnel
2.
Use a glass rod to help the
flow. The filter paper acts
as a sieve
3.
The liquid will pass though
the filter paper. The solid
are retained on the filter
paper as residue. It includes
sodium chloride inside.
How can we take the pure sodium chloride? (2)
Ⅱ. Crystallization
Sea water is allowed to evaporate at room temperature. The solution
becomes more concentrated. Lastly the solution becomes saturated. And the
evaporation of the solution will cause pure sodium chloride crystals to separate
out. If the evaporation continues, the solid crystals will grow in size slowly.
Ions of pure sodium chloride consisted
Ⅰ. Sodium ions (test for sodium ions)
1.
Dip the platinum wire into
a crushed or solution of
salt to test
2.
Heat strongly in a nonluminous flame
3.
Then, we can see that
there is given out a golden
yellow flame
So we can know that pure sodium chloride is included
sodium ions inside.
Ions of pure sodium chloride consisted (2)
Ⅱ. Chloride ions (test for chloride ions)
1.
Add silver nitrate solutions
to sea water
2.
Followed excess dilute
nitric acid
3.
Appearance of a white
precipitate indicates the
presence of chloride ions
So we can also know that, pure sodium chloride is included
chloride ions inside.
Electrolysis of sea water
After seeing the details
about sodium chloride, we will
change our focus on electrolysis
of sea water.
Using common salt to preserve fish
Sea water is an essential
source of common salt (sodium
chloride) which has many uses,
such as using common salt to
preserve fish. But we can get
much more useful products by
the electrolysis of sea water.
Electrolysis of sea water (2)
Electrolysis means “decomposition by electricity”.
It’s usually carried out by passing a direct electric
current through an aqueous salt solution. When sea
water is electrolyzed, the products are hydrogen,
chlorine and sodium hydroxide. There is a concentrated
solution of sodium called brine, which is used instead of
sea water. Their main products are the same. Let’s see
the uses of products in next page.
Uses of products
The uses of products (rocket fuel, soap, bleach, etc) are
very useful for our life!
Conclusion
We think that sea water (or oceans) is very important
for our life. First, it acts the habitats of benthos. And we
can take pure water by some methods, let us have water to
use. Also, the sea water after electrolyzed, can help for our
life a lot. It produces three kinds of products (gas/liquid),
they help to fabricate some commodities, or treatment of
water. It may also help for the development of industries,
like food industry. So that, it is unimaginable that there are
no any oceans or sea water in the world, it will let us very
uncomfortable. But it may be there will be exhausted in the
future. Therefore we should protect the ocean, don’t let
them polluted.