Shapes
Make A Lot of Difference
Shapes
Make A Lot of Difference!!
Why does “ice float on water”?
Shape
Makes A Lot of Difference
All these contain water.
Why can water dissolve many things?
Shape
Makes A Lot of Difference
Why can I swim in water on a hot summer day
but cannot step on sand for long?
What has shape got to do with all these
observations? Let’s see…..
Water’s Chemical Structure
H
H
O
H
H
H
H
O
O
H
H
O
Each water molecule consists of 2 atoms
of hydrogen atoms bonded to an atom of
oxygen. The chemical formula of water
is H2O.
Water’s Chemical Structure









The oxygen atom attracts the electrons shared with
hydrogen atoms more strongly to itself. In effect,
each hydrogen atom acquires a partial (+) charge.
Oxygen acquires a partial (-) charge.
Water’s Chemical Structure
H
104.5o

H
104.5o
H


O

H

O

H
104.5o

H

O

The uneven distribution of electrical charges makes
water a polar molecule. The two O-H bonds make an
angle of 104.5o between them giving the molecule a
triangular shape.
Water Forms Hydrogen Bonds
H-bond
O

H


Water molecules are attracted to each other
creating hydrogen bonds. The attraction of
the oxygen of one molecule to the hydrogen
of another molecule forms the hydrogen
bond.
Water Forms Hydrogen Bonds
H-bonds
H-bonds
More hydrogen bonds are formed when
water molecules move closer to one another.
Water Forms Hydrogen Bonds
H-bonds
In solid water or ice, the molecules form
themselves into a well-ordered crystalline
structure (hexagon) held by hydrogen bonds.
Water –The Unique Solvent
Water
and
sugar
salt
lime
potassium
nitrate
lead
nitrate
Our experiment showed that water can
dissolve different kinds of solids like
salt, sugar, lime, and chemical salts like
potassium nitrate and lead nitrate.
Water –The Unique Solvent
Water
and
alcohol
vinegar
muriatic
acid
lye
oil
gasoline
Not only solids, water can dissolve different
kinds of liquids. It can dissolve alcohol,
vinegar, lye, and muriatic acid. But, it cannot
dissolve oil and gasoline.
Water –The Unique Solvent
Water
and
oxygen
carbon
dioxide
sulfur
dioxide
chlorine
Even gases dissolve in water but to a very
limited extent. The bubbles coming out of
the test tubes are gases that were dissolved
in water under pressure.
Water –The Unique Solvent
Here is a sample data gathered from a
library research. It was found out that the
solubility of many salts increases with
increase in temperature.
Substance
Solubility (g solute/100g water)
10oC
30oC
50oC
Lead nitrate
48.3
66.0
85.0
Sodium chloride
35.8
36.3
37.0
Potassium nitrate
20.9
45.8
85.5
7.0
20.0
34.0
Potassium dichromate
Water – The Unique Solvent
Data has been translated into a bar graph to show the comparative
increase in solubility of the solutes at 10oC, 30oC, and 50oC.
Solubility of Solutes at Varying Temperatures
Solubility (g solute/ 100g water)
90.00
80.00
70.00
60.00
Lead Nitrate
50.00
Sodium
Chloride
Potassium
Nitrate
Potassium
Dichromate
40.00
30.00
20.00
10.00
0.00
10oC
30oC
Temperature
50oC
Water –The Unique Solvent
A bar graph of the data.
Solubilities of gases in water
Solubilitie s (g s olute /
100g w ate r)
1 8.000
1 6.000
1 4.000
1 2.000
10oC
1 0.000
30oC
8.000
50oC
6.000
4.000
2.000
0.000
Sul f ur di oxi de
Chl or i ne
Car bon di oxi de
Gases
Oxygen
Water –The Unique Solvent
On the other hand, the solubility of
many gases decreases with increase
in temperature.
Substance
Solubility (g solute/100g water)
10oC
30oC
50oC
16.210
7.800
0.393
Chlorine
0.997
0.572
0.393
Carbon dioxide
0.232
0.126
0.076
Oxygen
0.005
0.005
0.003
Sulfur dioxide
Water – The Unique Solvent
Data has been translated into a bar graph to show the comparative
increase in solubility of the gases at 10oC, 30oC, and 50oC.
Solubilities of gases in water
Solubilities (g solute /
100g w ater)
1 8.000
1 6.000
1 4.000
1 2.000
10oC
1 0.000
30oC
8.000
50oC
6.000
4.000
2.000
0.000
Sul f ur di oxi de
Chl or i ne
Car bon di oxi de
Gases
Oxygen
Water – The Unique Solvent
Data has been translated into a bar graph to show the comparative
increase in solubility of the gases at 10oC, 30oC, and 50oC.
Solubilities (g solute /
100g water)
Solubilities of gases in water
1 8.000
1 6.000
Sulfur
dioxide
Chlorine
1 4.000
1 2.000
1 0.000
Carbon
dioxide
Oxygen
8.000
6.000
4.000
2.000
0.000
1 0oC
30oC
Temperature
50oC
Water –The Unique Solvent
The graph shows that …
1.
2.
3.
In general, the solubility of a solid in water
increases with increase in temperature. The
degree of increment varies with the nature of
the solid.
The increase in solubility of sodium chloride is
relatively small, thus, a temperature increase
has a slight effect on the solubility of sodium
chloride in water.
The increase in solubility of potassium nitrate is
relatively large, thus a temperature increase
has a large effect on the solubility of potassium
nitrate in water.
Water –The Unique Solvent
The graph shows that …
1.
In general, the solubility of a gas in water
decreases with increase in temperature. The
decrease varies with the nature of the solute.
2.
Sulfur dioxide has the highest solubility under
the same temperature, and experience the
greatest decrease in solubility when its
temperature is increased.
3.
The solubility of oxygen is very, very small
(almost negligible) and seem unaffected by an
increase in temperature.
Water – The Unique Solvent
Na+
Cl-
A sodium chloride unit (NaCl) consists
of a sodium ion and a chloride ion.
What happens when NaCl is added to
water?
Water – The Unique Solvent
Several sodium chloride (NaCl) units
make up a sodium chloride crystal.
Na+
Cl-
NaCl
Water – The Unique Solvent
Water exerts an attractive force on NaCl with the Cl side attracted to the H of water
and the Na side to the O of water.
 O
Na+
H 
Cl-
Water – The Unique Solvent
The attractive force is strong enough to break
the bonds between Na+ and Cl- ions, and the ions
break away from their positions in the crystal.
They are quickly surrounded by the water
molecules.
Water – The Unique Solvent
The same thing happens when other ionic
substances like potassium chloride, calcium
chloride, sodium nitrate, and polar substances
like alcohol, vinegar and muriatic acid dissolve
in water.
ClK+
ClK+
KCl
ClK+
Water – The Unique Solvent
Write
these:
1. Why is seawater salty? Where did the
salts come from?
2. Water is a poor solvent to many nonpolar
substances like oil and gasoline. They form
layers with water usually occupying the
lower layer. What is the effect of oil
spills on rivers and lakes and the living
things in it?
3. What is the effect of an increase in
temperature on the amount of dissolved
oxygen in a river or lake?
Some Applications
The high solubility of alcohol in water
makes possible
a) the preparation of wines,
colognes,perfumes,
rubbing alcohol, etc..
b) the rapid spread of ethyl alcohol
(from alcoholic drinks) in the body
because the body is made up of 75%
water.
Some Applications
Fire caused by gasoline
or oil cannot be put off
by dousing it with water.
Water will sink and form
the lower layer. The oil or
gasoline will form the upper
layer and spread out,
exposing more of it to
oxygen.
Some Applications
The low solubility of oxygen
in water limits its presence
in water. This dissolved
oxygen is used by fish and
other organisms in rivers,
lakes, etc.in order to live.
Some Applications
An increase in temperature
of the water will further
reduce the dissolved oxygen,
further lowering the available
oxygen for these living
things.
Some Applications
Rainwater dissolves certain
gases in air as it falls to
the ground, seas, and
oceans. As it flows
through soil and rock
formations, it dissolves
many mineral salts and
carries with it countless
bacteria.
Well, these are all for today, class.
I hope you learned from the experiments we
did and from the presentation.
Until our next meeting….. BYE!!