Physical and Chemical
Properties of Water
The Water Molecule
Water is a compound
Compound: substance that contains
two or more different elements.
H2O: 2 hydrogens and 1 oxygen
A water molecule is held together by
a Covalent Bond.
Molecules are held together by
2 or more water molecules are held
together by Hydrogen bonds
Hydrogen Bond-When a hydrogen
atom is linked to another atom by
electrostatic forces. Much stronger
than covalent bonds.
Gives water properties such as
cohesion and adhesion.
A Polar Molecule
Molecule behaves like a magnet.
Its positive end attracts
negatively charged particles
Its negative end attracts
positively charged particles
Most salts are held together by
opposite charges (Na+, Cl- is
NaCl) and when these come in
contact with water, they are
This is why water is a good
Solvent (dissolve things well).
Properties of Hydrogen
Cohesion-Allows individual water molecules to stick to
each other (cluster), giving water a high surface tension.
It also allows for diffusion. (think of the water on the
penny or paper clip on water…this is due to cohesion
and surface tension).
Adhesion-The tendancy of water to stick to other
materials (making them wet). (capillary action in soil or
water running up a paper towel).
Physical Properties of Ocean
Ability to transmit light
Ability to transmit sound
Heat: A measure of energy produced by vibration of
atoms or molecules.
Temperature: A measure of how rapidly molecules are
Heat Capacity: The amount of heat it takes to raise 1
gram of a substance by 1 degree Celsius.
Water has highest heat capacity of any substance.
From hydrogen bonding!
Means water’s temperature does not rise or lower very
Calories per gram
Heat=Specific Heat x
Change in Temperature
How would we calculate
Temperature and Density
Water becomes more dense
as it gets colder.
UNTIL: It reaches 4 degrees
Then water becomes less
dense as it freezes
Why does this happen?
Salinity and Density
Note that a higher salinity
gives water a higher density.
Note also that salinity
decreases the temperature
at which water freezes
So ocean water freezes at
about -2 degrees Celsius
Fresh water freezes at 0
Temperature, Salinity, Density
Note that two samples of water can have
the same density at different combinations of
temperature and salinity.
Density of Seawater is 1.020-1.030 g/cm3
Fresh is only 1.000 g/cm3
Cold, salty water is more dense than warm, less salty
Seawater’s density increases with increasing salinity,
increasing pressure, and decreasing temperature (until
right before it freezes).
Two samples of water can have the same density at
different combinations of temperature and salinity.
Light in the Ocean
are absorbed at
levels and is
-To our eyes.
this is why the
Photic Zone: The depth light penetrates in the ocean.
200 meters in clear, tropical waters
100 meters in most ocean waters
All photosynthetic organisms live in this zone (corals, sea
grasses, algae, phytoplankton).
Infrared radiation is converted to heat
Most of life in the ocean is found here.
Aphotic Zone: Zone below photic zone that is in
About 1% of light penetrates to a depth of 100-125
Absolutely no light penetrates below 1,000 meters.
¾ or 75% of the ocean is in total darkness!
Refraction: Bending of waves. Light acts as a wave
and a particle.
Light bends toward
When it travels
From a lower
Density to higher
Light bends away from
The normal when it
Travels from higher density
To lower density.
Sound in the Ocean
Sound: Form of energy transmitted through a medium
through vibration of molecules.
Sound intensity decreases through seawater due to
spreading, scattering, and absorption.
Sound travels about 1,500 m/s in seawater
Sound travels 334 m/s in air at 20 degrees C.
Speed of sound increases as temperature, pressure, and
Low frequencies travel farther than high frequency
The minimum velocity layer
1200 m depth in North Atlantic down to 600 m depth in
Sound waves move at minimum speed and allow for
sounds to heard for great distances since refraction
keeps sounds waves within the layer.
Maximum sound velocity occurs at 80 m which deflects sound and causes
a shadow zone.
SONAR: Sound Navigation and Ranging.