Water 1
WATER
2
“The solvent of Life”
The mother liquor for all forms of life.
In human 70% of lean body weight of an adult is composed of
water.
Our normal body temperature of 37°C is maintained mainly
because water is expelled by lungs and skin.
PHYSICAL PROPERTIES OF WATER 3
The physical properties of water differ from those of other solvents.
Water is hydride of oxygen (H2O). Possessing higher melting point,
boiling point, heat of vaporization and surface tension as compared
to hydrides of Sulphur (H2S), nitrogen (NH3) etc.
The unusual properties are a consequence of strong attractions
between adjacent water molecules, which give liquid water great
internal cohesion.
PHYSICAL PROPERTIES OF WATER 4
FEATURES OF WATER 5
POLARITY OF WATER 6
Covalent or ionic bond b/w two items depends upon
electronegativity of items.
In water, an oxygen atom shares electrons with 2 hydrogen atoms.
But the shared electrons are more concentrated around the oxygen
nucleus than around the 2 hydrogen nuclei.
POLARITY OF WATER 7
Consequently, the oxygen atom has a slight negative charge and the 2
hydrogen atoms have a slight positive charge.
Molecules that have uneven distributions of electrical charge are said to
be polar, since they have positive and negative poles in the same way
that a magnet has 2 poles.
When a polar molecule, such as water, comes close to an ion or to
another polar molecule, its negative pole points toward the other
molecule’s positive pole, and its positive pole toward a neighboring
negative pole. Molecules with approximately uniform charge
distributions are said to be nonpolar.
HYDROGEN BONDING 8
When a hydrogen atom attaches to a highly electronegative atom such as
oxygen or nitrogen, the resulting covalent bond is polar. In this case, the
hydrogen atom acquires a slight positive charge. Such a hydrogen atom
can then participate in a Hydrogen bond (a weak interaction to a
negatively-charged atom in another molecule).
The most common hydrogen bonds are between water molecules,
Other hydrogen bonds play a critical role in the structure of proteins and
DNA.
Hydrogen bonds are weaker than covalent bonds.
