Transcript Properties of Water - Save water,save Life.

SAVE WATER!
SAVE LIFE!
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Plan
– In our presentation, we will follow the following plan:
• 1) Water as the cradle of life
• 2) Physical and chemical properties of water
• 3) Pollution of water
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Part 1
Water – the cradle of life
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Water – the cradle of life
• For proving the importance of water for the birth of life, we will take
a look at the as known chemical evolution – the transition from
inorganic materials to the simplest and fundamental form of life as
we know it – the first cells.
• The cells are the basic structure, metabolic and functional unit of
organisms.
• The evolution of life after the creation of cells is known as biological
evolution, and we are not going into it in this presentation.
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This tree shows the
evolution of primary
chemical elements until
the forming of life as we
know it. Notice that the
greater part of evolution is
before the formation of
the first cells.
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Life as we know it
First cells
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Conventional border
Protobionts
Protobionts
Biopolymers
Biopolymers
Low mass
organic
aggregates
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3
2
1
N2 CO NO
2
Initial gases NH3
CO2
H2
CH
H2O 4
Primary Earth
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Initial gases
1 stage
Active volcanoes
N2
CO
CO2 H2
NH3 CH4
NO2
H2O
• 1. Probably during the early stages of the Earth’s existence there
were violent volcanic eruptions on the whole surface, congestion of
the Earth’s crust and separation of a high amount of heat. The
gases (water vapours, hydrogen, methane, ammonia), coming from
the hot semi-fluid interior of the Earth, formed the atmosphere. It
contained the basic materials for the formation of organic
combinations.
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2 stage
Methane
Benzene
Soap
• The gases, contained in the atmosphere, reacted with each other
and formed organic molecules. The energy for this synthesis came
from the lightning and the ultra-violet radiation. Gradually the Earth
became cold and when the temperature fell below 100˚С, the water
vapours began to condense, the rain evaporated from the hot
surface and this initiated the circle of water. The folding proccesses
led to the forming of giant hollows. They filled with water and
formed the oceans and the seas.
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Miller’s experiment
• An evidence for this is the
experiment of Stanley Miller. He
invented a device in which
ammonia, methane, hydrogen and
water vapours circulated and
through the mixture passed an
electric spark. During the
circulation the water cooled and
fell like a “rain”. After a week in
the liquid were found amino acids.
It is perfectly possible that the
same processes happened in the
atmosphere.
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3 stage
• Some primitive nucleic acids acquired matrix ability and were able to form a
• The
organicThe
combinations
reacted
eachcharges
other stuck
and
copy simple
of themselves.
macromolecules
with with
opposite
formed
albumens,
nucleic
acids, carbohydrates
and
lipids,
together simple
and formed
aggregates
- complexes
of over-molecule
level.
The
which
constantly
evolved.
albumensin formed
hydrophilic
colloidal
rain carried
away the
organic The
combinations
the oceans
and the seas,
where
the so-called
formed.molecules.
complexes,
which “organic
attractedsoup”
the water
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4 stage
Coacervate
••
•
Enzymes were formed in the coacervates through absorbing metal ions.
On the surface of some coacervates more lipids and albumens gathered and
The
coacervates areof
very
drops,
which have
characteristics.
Some
thesmall
organic
molecules
theosmotic
coacervates
became
formedcombinations
a double molecule
layer.
With
time theincover
of some coacervates
Around
theadded
complexes
of over-molecule
level a waterwere
cover
differentiated.
stable
their
organization,
destroyed.
becameand
permeabletoand
some
reactions while
whichothers
released energy
began.The
The
In
this
system
the
molecules
interacted
with
each
other
and
new
molecules
complexes
over-molecule
level
in them were
much
more
complicated
membrane of
gave
stability to the
coacervates.
This
is the
precellular
period in
entered through the cover, thus enlarging the drop.
the
matter.
thanevolution
these in of
theorganic
environment.
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5 stage
• Molecules which already existed in the organic soup and could replicate
were included in the coacervates. As a result of this a rearrangement of the
interior contents began. The transport of materials through the cellular
membrane perfected. The nucleic acids established control over the basic
life processes. The protocells could split and share their genetic program
with their filial cells. The cellular period of the evolution of the animate
nature began.
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• … and life began …
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Part 2
Properties of water
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Water has no taste, no colour, no odour; it cannot be defined,
art relished while ever mysterious.
Not necessary to life, but rather life itself. It fills us with a gratification
that exceeds the delight of the senses.
ANTOINE DE SAINT-EXUPERY (1900-1944), Wind, Sand, and Stars, 1939
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Planet, dominated by water
• We live on a planet that is
dominated by water.
• More than 70% of the Earth's surface
is covered with this simple molecule.
Scientists estimate that the
hydrosphere contains about 1.36 billion
cubic kilometers of this substance
mostly in the form of a liquid (water)
that occupies topographic depressions
on the Earth. The second most
common form of the water molecule
on our planet is ice. If all our planet's
ice melted, sea-level would rise by
about 70 meters.
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• Water is also essential for life.
Water is the major constituent of
almost all life forms. Most
animals and plants contain more
than 60% water by volume.
Without water life would
probably never have developed
on our planet.
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Structure of water molecule
• The two hydrogen atoms bound to one oxygen
atom to form a 'V' shape with the hydrogen
atoms at an angle of 105°.
• When the hydrogen atoms combine with
oxygen, they each give away their single
Oxygen
electron and
form atom
a covalent bond. Because
electrons are
more attracted
to the positively
Hydrogen
atom
charged oxygen atom, the two hydrogens
Covalent bond
become slightly positively charged (they give
away their negative charge) and the oxygen
atom becomes negatively charged.
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Polar molecule
+
-
-
• This separation between negative and positive charges
produces a polar molecule, that is a molecule that has an
electrical charge on its surface. The hydrogen lobes have
positive charges, and the oxygen atom on the opposite side
has two negative charges (associated with two lobes.)
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Hydrogen bond
• Because they are polarized, two
adjacent H2O molecules can form a
linkage known as a hydrogen bond.
• Hydrogen bonds have only about
1/20 the strength of a covalent bond.
A hydrogen bond is therefore a weak
chemical bond between a hydrogen
atom in one polar molecule and a
very electronegative atom of a
second polar molecule. The hydrogen
of one water molecule will be
attracted to the oxygen of another
water molecule. There are usually 48 molecules per group in liquid water.
+
-
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• The water molecules form hydrogen bonds, giving shape to
water as a liquid. Each single water molecule can form
bonds with four other water molecules in a tetrahedral
arrangement. Although these bonds are weak they lead to
many other unique properties.
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3 aggregate conditions
• Water is found on Earth in all
three forms: liquid, solid, gas, and
is cycled though the water cycle.
• Water is unique in that it is the
only natural substance that is
found in all three states -- liquid,
solid (ice), and gas (steam) -- at
the temperatures normally found
on Earth. This is because the
Earth is a very special planet with
just the right range of
temperatures and air pressures.
Earth's water is constantly
interacting, changing, and in
movement.
 Water cycle.
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Water properties
• Water as a liquid has the following properties:
• Water is a tasteless, odourless liquid
at ambient temperature and pressure,
and appears colourless, although it
has its own intrinsic very light blue
hue. Ice also appears colourless, and
water vapor is essentially invisible as
a gas.
• Tasteless
• Odourless
• Colourless
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Transparency
• Water is transparent, and thus aquatic
plants can live within the water because
sunlight can reach them. Only strong UV
light is slightly absorbed.
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Conductivity
• Conductivity is the ability
of a substance to carry
an electric current.
• Water will conduct an
electric current only if
dissolved ions are
present because water
molecules do not act as a
conductor. Measuring
conductivity is a good
way to determine the
amount of dissolved
solids in a sample of
water and, thus, to
determine its purity.
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Water’s extension
• Most liquids contract (get smaller) when they get colder. Water is different -
it contracts until it reaches 4 C then it expands until it is solid. Solid water is
less dense than liquid water because of this.
•
•
•
Water
If
water
becomes
worked even
like other
less dense
liquids,upon
The
boilingbe
point
and
thenhigher
freezing,
thereexpanding
would
9%.
no such
Thismelting
thing
causes
point
of
can
by the
as
an
an
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icewater
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phenomenon:
the be
iceexplained
in your
icefor
floats
soft
Hydrogen
bonding
accounts
the
hydrogen
help
hold
groups
drink
upon
would
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and that
so
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bottom
organisms
of helpsof
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wood.
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water
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andofponds
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explain
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hydrogen
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onThe
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of water.
Water
boils
atthe
and
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into
the air.
density
temperature
of water
of around
is
at escape
3.98
4sulfur
°C°C(39
°F).
at 0°C.molecules
By
comparison,
dioxide,
a
This
requires
energy
in
the
form
of
heat.
(39.16
°F).
molecule of similar size, boils at 62°C and
Molecules
freezes at such
-83°C.as sulfur dioxide and
carbon dioxide do not have hydrogen
bonds and, consequently, require less
energy to boil.
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Thermal capacity
• Water has one of the highest heat
capacities of all substances.
• This means that it takes a great
deal of heat energy to change the
temperature of water compared to
metals.
• The large amount of water on
Earth means that extreme
temperature changes are rare on
Earth compared to other planets.
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Thermal buffer
• Were it not for the high heat capacity of water, our bodies (which
also contain a large amount of water) would be subject to a great
deal of temperature variation.
• By the two ways of defending against overheating (high heat
capacity and high warmth of evaporation) water actually is an ideal
medium for life and ensures safe temperature conditions in the
organic systems. They also allow water to moderate Earth's climate
by buffering large fluctuations in temperature.
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Adhesion
• Water molecules stick to each other. This is
called cohesion. Water can also be attracted
to other materials. This is called adhesion.
• Water has a partial negative charge (σ-) near the oxygen atom due to
the unshared pairs of electrons, and partial positive charges (σ+) near
the hydrogen atoms. In water, this happens because the oxygen atom is
more electronegative than the hydrogen atoms — that is, it has a
stronger "pulling power" on the molecule's electrons, drawing them
closer (along with their negative charge) and making the area around
the oxygen atom more negative than the area around both of the
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hydrogen atoms.
Capillary action
• Capillary action is related
to the adhesive properties
of water.
• Plants take advantage of
capillary action to pull
water from the earth into
themselves.
• You can see capillary
action 'in action' by
placing a straw into a
glass of water.
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• What is happening is that the water
molecules are attracted to the straw
molecules. When one water
molecule moves closer to the straw
molecules the other water
molecules (which are cohesively
attracted to that water molecule)
also move up into the straw.
• Capillary action is limited by ...
gravity and the size of the straw.
The thinner the straw or tube the
higher up capillary action will pull
the water.
The water 'climbs' up the straw.
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High surface tension
 Water has a very high surface
tension. In other words, water is
sticky and elastic, and tends to
clump together in drops rather
than spread out in a thin film.
Surface tension is responsible for
capillary action, which allows
water
(and
its
dissolved
substances) to move through the
roots of plants and through the
tiny blood vessels in our bodies
 Surface tension is related to the
cohesive properties of water
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• This phenomenon also causes
water to stick to the sides of
vertical structures despite gravity's
downward pull. Water's high
surface tension allows for the
formation of water droplets and
waves, allows plants to move
water (and dissolved nutrients)
from their roots to their leaves,
and the movement of blood
through tiny vessels in the bodies
of some animals.
This insect walks on the water’s surface
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Universal solvent
• Water is a very strong solvent, referred to as
the universal solvent, dissolving many types
of substances.
• Substances that will mix well and dissolve in
•
water, e.g. salts, sugars, acids, alkalis, and
some gases: especially oxygen, carbon
dioxide (carbonation), are known as
Hydrophilicsalts,
sugars,substances,
acids, alkalis,
“hydrophilic"
(water-loving)
while those that
not mix
well with water
anddosome
gases
(e.g. fats and oils), are known as
“hydrophobic" (water-fearing) substances.
Hydrophobicfats
and oils in a liquid, the
When
a substance dissolves
mixture is termed a solution. The dissolved
substance (in this case sugar) is the solute,
and the liquid that does the dissolving (in
this case water) is the solvent.
NaCl
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• They dissolve in water, because their molecules separate from
each other, each becoming surrounded by water molecules.
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pH balance
• Water in a pure state has a
neutral pH. As a result, pure water
is neither acidic nor basic. Water
changes its pH when substances
are dissolved in it. Rain has a
naturally acidic pH of about 5.6
because it contains natural
derived carbon dioxide and sulfur
dioxide.
The pH of a sample of water is a
measure of the concentration of
hydrogen ions.
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Biochemical reactions
• Water is a regulator of biochemical reactions. All of them start and
complete by direct or indirect reaction with the water molecules in
the cell. The speed of the biochemical processes is reduced by the
reduction of water content under some limits.
• With tremendous odds against unicellular organisms, they exude
water, as a result of which the cytosol is condensed and the vital
processes are reduced to a minimum. This state of organisms is
called 'vita minima' or anabiosis. At optimal living conditions the
amount of water in the organisms gets back to normal and the
constitution is restored to its normal active state.
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Afterword
• Water is closely connected not only with the birth of life, but with
its evolution as well. It has always been a limiting factor. The lack
of water is one of the main forces controlling the natural
selection. All terrestrial organisms take water and preserve it by
some means or other. Clear examples can easily be found among
desert ones such as cacti and camels.
• Once the unique role of water in the living systems was
expressed by a prominent biochemist Szent-Dyerdyi in the
phrase: “Water is not only a mother, but a matrix of life”. That is
why everybody should take thought of it.
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Conclusion :
• Save water!
• Save life!
Author: Diana Sofronieva
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