Water is a polar molecule comprised of an oxygen atom covalently bonded to two hydrogen atoms at an angle of 104.5 degrees. This polar structure results in slightly positive and negative charges on opposite sides of the molecule. Water molecules can form hydrogen bonds between the slightly positive hydrogen of one molecule and the slightly negative oxygen of another. These hydrogen bonds give water important properties like surface tension, capillary action, and allowing it to dissolve many other polar substances. Water can also exist as a liquid, solid (ice), and gas (water vapor) and plays a vital role in all living things.

2.  Water is essential for life.It covers 2/3 of the
earth’s surface and every living thing is
depend upon it.
 The human body is comprised of over 70%
water,and it is a major component of many
body fluids including blood,urine,and saliva.

4.  Water is formed when two hydrogen atoms
bond to one oxygen atom.
 With a total atomic weight of 18 daltons

5. O
H H
1 molecule of water

6.  The structure of the electrones surrounding
water is tetrahydral,resembling a pyramid.
 The angle between H-O-H bond is
109.547degree.

7.  There is a great concentration of electrones
around the nucleus of the oxygen than
around the hydrogen.
 There for,the hydrogen end is slightly
positive and the oxygen end is slightly
negative.

8.  The oxygen end “acts” negative
 The hydrogen end “acts” positive
 Causes the water to be POLAR, like a
magnet.

9. What is polar?
Molecules can be grouped as polar or non- polar
molecules.
The arrangement or geometry of the atoms in
some molecules is such that one end of the
molecule has a positive electrical charge and
the other side has a negative charge.if this is
case,the molecule is called polar
molecule,meaning that has electrical
poles.Otherwise it is called non-polar.

10.  Formed between a highly
Electronegative atom (like
oxygen in another water)
of a polar molecule and a
hydrogen
 Weak bond, but strong in
great numbers.

11. Negative Oxygen end of one water molecule is attracted to the Positive
Hydrogen end of another water molecule to form a HYDROGEN BOND

12.  Water is the only substance found on Earth
in all three states (phases):

13. 1. Liquid

14. 2. Solid (Ice)

15. 3. Gas (Steam or Vapor)

17. 1.PHYSICAL PROPERTIES
2.CHEMICAL PROPERTIEs

18. 1. Physical Properties
 Polar molecule
 Hydrophilic substances dissolve
 Hydrophobic substances aggregate
 Osmosis
 Cohesion
 Adhesion

19. Water is a polar molecule because of the
way the atoms bind in the molecule with
more positive(+) charges on one side of the
molecule and more negative(-) charges on
the other side of the molecule.In other
words the hydrogen atoms group on one
side of the molecule making that more
positive,such that there are more electrons
from the oxygen atom on the other side of
the molecule.

20.  A water molecule is formed when two atoms
of hydrogen bond covalently with an atom of
oxygen.
 In a covalent bond electrons are shared
between atoms. In water the sharing is not
equal. The oxygen atom attracts the
electrons more strongly than the hydrogen.

21.  This gives water an asymmetrical distribution of
charge.
 Molecules that have ends with partial negative and
positive charges are known as polar molecules.
 It is this polar property that allows water to
separate polar solute molecules and explains why
water can dissolve so many substances.

22.  The HOH bond angle is 104.5
 The oxygen nucleus attracts electrons more
strongly than does the hydrogen nucleus (a
proton);
 that is, oxygen is more electronegative.
 The sharing of electrons between H and O is
therefore unequal;

23.  The result of this unequal electron sharing is
two electric dipoles in the water molecule:
 one along each of the H O bonds:
 each hydrogen bears a partial positive charge
 And the oxygen atom bears a partial negative
charge equal to the sum of the two partial
positives

24.  As a result, there is an electrostatic attraction
between the oxygen atom of one water
molecule and the hydrogen of another called
a hydrogen bond.

26.  Hydrophilic & Hydrophobic
 Water is a polar solvent. It readily dissolves
most biomolecules, which are generally
charged or polar compounds.

27.  Compounds that dissolve easily in water are
hydrophilic (Greek, “water-loving”).
In contrast,
 Nonpolar solvents such as chloroform and
benzene are poor solvents for polar
biomolecules but easily dissolve those that are
hydrophobic—nonpolar molecules such as
lipids and waxes.

28.  Water dissolves salts such as NaCl by hydrating
and
stabilizing the Na and Cl ions, weakening the
electrostatic interactions between them.
 The same factors apply to charged biomolecules,
 Water readily dissolves such compounds by
replacing solute- solute hydrogen bonds with
solute-water hydrogen bonds, thus screening the
electrostatic interactions between solute
molecules.

29. Amphipathic compounds contain regions that
are:
 Polar (or charged) and regions that are
Nonpolar.

30.  When an amphipathic compound is mixed with
water, the polar hydrophilic region interacts
favorably with the solvent and tends to
dissolve.
 but the nonpolar, hydrophobic region tends to
avoid contact with the water.

31.  These stable structures of amphipathic
compounds in water are called micelles, May
contain hundreds or thousands of molecules.
 Many biomolecules are amphipathic; e.g
Proteins, pigments, certain vitamins, and the
sterols and phospholipids of membranes all
have polar and nonpolar surface regions

32.  The forces that hold the non polar regions
of the molecules together are called
hydrophobic interactions.
 (nonpolar compounds self associate in an
aqueous environment)

33.  Hydrophobic interactions among lipids, and
between lipids and proteins, are the most
important determinants of structure in
biological membranes.
Hydrophobic interactions between non
polar amino acids also stabilize the three-
dimensional structures of proteins.

34.  Osmosis is the passage of water from a
region of high water concentration
through a semi-permeable membrane to a
region of low water concentration.
osmosis , transfer of a liquid solvent
through a semipermeable membrane that
does not allow dissolved solids (solutes)
to pass.

36.  Salt is a solute, when it is concentrated
inside or outside the cell, it will draw the
water in its direction.

38.  If the concentration of solute (salt) is equal
on both sides, the water will move back in
forth but it won't have any result on the
overall amount of water on either side.
 "ISO" means the same

40.  The word "HYPO" means less, in this case
there are less solute (salt) molecules
outside the cell, since salt sucks, water will
move into the cell.

42.  The word "HYPER" means more, in this case
there are more solute (salt) molecules outside
the cell, since salt sucks, water will move out
of the cell.

43.  The word "HYPER" means more, in this case
there are more solute (salt) molecules outside
the cell, since salt sucks, water will move out
of the cell.

44.  The process of osmosis and the factors that
influence it are important clinically in the
maintenance of adequate body fluids and in
the proper balance between volumes of
extracellular and intracellular fluids.

45.  Have you ever filled a glass of water to the very
top and then slowly added a few more
drops?Before it overflows,the water forms a
dome-like shape above the glass.this dome like
shape forms due to the water molecules
cohesive properties,or their tendency to stick to
one another.
 Cohesive refers to the attraction of molecules
for other molecules of same kind,and water
molecules have strong forces thanks to their
ability to form hydrogen bonds with one another.

46.  Cohesive forces are responsible for surface
tension,the tendency of a liquid’s surface to
resist rupture when placed under tension or
stress.

47.  Water has a greater surface tension than most
other liquids because hydrogen bonds among
surface water molecules resist stretching or
breaking the surface.
Some animals can stand,
walk, or run on water
without breaking the
surface

48. o Adhesion is the attraction of molecules of
one kind for molecules of a different kind,and
it can be quite strog for water,especially with
other molecules bearing positive or negative
charges.
o For instance,adhesion enables water to
‘climb’ upward through thin glass
tubes(called capillary tubes) placed in a
beaker of water. This upward motion against
gravity known as capillary action

49.  This depends on the attraction between
water molecules and the glass walls of the
tube(adhesion),as well as on interaction
between water molecules(cohesion)

50. WATER
DROPLET
WINDSHIELD Adhesion is going
on between the
windshield and the
water droplet.

51. Which gives water the
ability to “climb”
structures

52. 2.Chemical properties
 Dissociation of water molecules
 Acids and bases

53.  Occasionally, a hydrogen atom shared by two
water molecules shifts from one molecule to
the other.
› The hydrogen atom leaves its electron behind and
is transferred as a single proton - a hydrogen ion
(H+).
› The water molecule that lost a proton is now a
hydroxide ion (OH-).
› The water
molecule with
the extra proton
is a hydronium
ion (H3O+).
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Unnumbered Fig. 3.47

54. One water molecule is made of two ions,
(H+) and a Hydroxide Ion (OH-)
Hydrogen Ion Hydroxide Ion
Acid Base
H2O  H+ + OH-

55. Acid: A solution with lots of H+ ions
• pH 0 up to 7 is acid (acidic)
Base: A solution with lots of OH-
ions
• pH above 7 – 14 is basic (alkaline)

56. Strong acids and bases
complete dissociate in
water.
Weak acids and bases
dissociate only partially and
reversibly.