Water and Seawater
Water Molecules and their
Characteristics
Atomic Structure
• The chemical properties of water are
essential for sustaining all life forms.
– Composing 65% of humans and 95% of plants
– Huma BLOOD is 83% water
• An atom are the basic building blocks of all
matter
Atomic Structure
• Atoms are composed of protons,
neutron, and electron
– Same amount of proton and neutron
– To balanced the charge also same amount
of electrons
• The number of protons is what makes
each element different from one another
– The number of electrons can change
making the atom have a charge ions
• Oxygen- 8 protons,8 neutrons, 8
electrons
• Hydrogen- 1 proton, 1 neutron, 1
electron
Atomic Structure
• Molecule is a group of two or more atoms
held together by mutually shared electrons
• Water Molecule H2O- one oxygen atom
covalently bonded to two hydrogen atoms at
an angle of 104.5 degrees
Intermolecular Forces
• The oxygen and hydrogen are covalently binds
to each other this is a strong bonds form due
to sharing of electrons
• The Bent geometry gives a negative charge to
the oxygen side and a positive charge to the
hydrogen side of the molecule
• Water is a polar molecule
– Has a partial positive and a partial negative side
– The oxygen is partial negative
– The hydrogen is partial positive
Hydrogen Bond
• Attraction between positive
and negative ends of water
molecules to each other or
other ions
• Oxygen, forms a weak H bond
• The hydrogen bond is much
weaker than a covalent bond
• Less energy is needed to be
broken
Properties of Water Due to H Bonds
• Cohesion- water molecules stick to
one another, causes it to bead up on
waxed surfaces
• Surface Tension- Water’s surface has
a thin “skin”. It’s a result from the
formation of hydrogen bonds
between the outermost layer of
water
Properties of Water Due to H Bonds
• Adhesion- water clings to
surfaces, will climb up the sides
of a glass test tube
• Capillary Action- very thin tubes
will allow water to climb up tube,
Plants use capillary action to
raise water to tops of trees
Properties of Water Due to H Bonds
• Universal Solvent- Water is
able to dissolve nearly
everything, given time it can
dissolve more substances in
greater quantity than any
known substance
– Water sticks to other polar
molecules, NaCl + sodium
sticks to - oxygen and –chloride
sticks to + hydrogen
Thermal Properties of Water
• Water exists as a solid, Liquid and a gas
at earths temperatures
• Has the capacity to store and release
great amounts of heat because the H
bonds must be broken
– These bonds are broken by either adding
heat (ice water) or removing heat (water
 ice)
• Heat is measured in calories(heat
required to raise 1 gram of water 1
degree centigrade)
Thermal Properties of Water
• In solid state water has a rigid structure
– Bonds are constantly being broken, vibrating,
by molecule remains in relative fixed position
• In liquid state water has a flexible structure
– Bonds are being formed and broken at a much
faster rate than in solid state, molecules still
interact but have more room to flow by each
other
• In gas state water molecules no longer
interact with each other except during
collision
Water Freezing and Boiling Points
• Water melts and boils at very high
temperatures due to H bonds
• For pure water the melting and freezing point
is 0℃ (32℉)
• For pure water the boiling point or
condensation point is 100℃ (212℉)
Water’s Heat Capacity
• Heat capacity is the amount
of heat required to raised
the temperature of 1 gram
of any substance by 1℃
• Water has a high heat
capacity – can take in or lose
much heat without changing
temperature
– This is because it takes more
energy to increase the kinetic
energy of hydrogen –bonded
water molecule
Water’s Latent Heats
• Latent heat is the amount of “hidden” heat
water has stores, which is related to water's
unusually high heat capacity
• As water evaporates from your skin, it cools
your body by absorbing heat (this is why
sweating cools your body)
• If you have ever been burned by water vapor,
this steam released an enormous amount of
latent heat when it condenses to a liquid
Thermal Properties of Water
• Latent Heat of melting- to go from solid to liquid just
enough H bonds are broken to allow water molecules
to slide past one another. (80 calories)
• Latent heat of Vaporization- to go from liquid to gas all
H bonds must be broken to allow water molecules to
move freely, (540 calories) water molecules vaporize
into air at 1000 mph
• Latent heat of Evaporation- conversion of liquid to gas
below the boiling point.
– To evaporate from the ocean surface at less than 100
degrees C water molecules take heat energy away from
surrounding water. Molecules left behind have less heat
which explains the cooling effect of evaporation ( requires
585 calories to evaporate, more H bonds must be
overcome)
Thermal Properties of Water
• Latent heat of Condensation Cooled water
vapor turns to liquid and releases heat to the
environment
– releases heat back into air, cooks food as a
steamer and releases enough energy to power
thunderstorms and Hurricanes.
• Latent Heat of Freezing Heat released when
water freezes
– is identical to that of melting( 80 calories)
Calories = heat being applied
Global Thermostatic Effects
• The Sun radiates energy to earth where some is stored in
the oceans
• Evaporation removes this heat energy and carries it high
into Atmosphere
• Cooler upper atmosphere causes condensation into clouds
and precipitation
• This cycle of evaporation and condensation carries huge
amounts of heat energy from lower warm latitudes to
Higher colder latitudes
• The heat exchange is efficient
• The thermal properties of water prevent wide variations in
Earths temperature, moderating Earths climate, makes life
possible on Earth.
Water Density
• Density = mass per unit volume, How tightly the molecules
of a substance are packed
– How heavy something is for its size
• Thermal contraction- density of most substances increases
as temp decreases
– Cold air sinks and warm air rises
• As pure water cools to 4℃ its density increases
• From 4℃ to 0℃ the density decreases (ice begins to form)
• Ice is less dense than water and floats, highly unusual for
substances
– Water stops contracting and actually expands, very unusual
– Freeze water bottle expands
• Water at 4 degrees C has a specific gravity of 1.000 g/cm
Seawater Salinity
• Enough salt is dissolved
in the ocean to cover the
entire earth in 500 feet
of salt
• Seawater also contains
chlorine, sodium, sulfur,
magnesium, calcium, and
potassium and 80 other
chemical elements
Seawater Salinity
• Salinity of the ocean is
3.5%, usually expressed as
parts per thousand (ppt)
35ppt, or 35 grams of salt
to every 1000 grams of
water
• Salinity variations in open
ocean 33 to 38 ppt, the
Baltic sea averages 10 ppt
Seawater Salinity
• Brackish water- where fresh
water rivers and rain mix with
salt water
– Lowers salinity
• Hypersaline- high evaporation
rates and limit open-ocean
circulation
– Red Sea averages 42 ppt , areas
with high evaporation rates like
inland Lakes, Great Salt Lake
Utah 280 ppt, Dead Sea 330ppt
Seawater Salinity
• Seasonal Variations in salinity
• Miami Beach
– 34.8ppt in October to 36.4ppt in May and June
– May – June high evaporation rate
• Columbia River Oregon
– 0.3ppt in April to 2.6ppt in May
– Low from vast fresh water input from Columbia River
• Tap water salinity below 0.8ppt
• Processes that Effect Salinity include Precipitation, river
runoff, melting and freezing sea ice, Icebergs,
evaporation
Seawater Salinity
• Decreasing salinity – adding fresh water to
ocean
– River Runoff, melting icebergs, melting sea ice
– Precipitation
• Increasing salinity – removing water from
ocean
– Sea ice formation
– Evaporation
Hydrologic Cycle
• Recycle water among the ocean,
atmosphere and continents
– Process that effects seawater salinity
•
•
•
•
•
Ocean 97.2%
Glaciers, Ice Caps 2.15%
Ground Water, Soil moister 0.62%
Rivers and Lakes 0.02%
Water Vapor in Atmosphere 0.001%
At the surface the salinity
differs a lot but not in the
deep. Why is that?
High salinity (orange and red areas) occur in areas of low latitude
Low salinity (blue and purple areas) occur in areas of high latitudes
Seawater Density
• Halocline- rapid
changes in salinity
between 300 and
1000 meters, Higher
salinity means higher
Density
• https://youtu.be/Q60XfLcSmdY
Seawater Density
• Thermocline – rapid
changes in temp
between 300 and
100 meters, warm
surface water with
layer of cold Denser
water underneath
– Abrupt change in
density with depth
Seawater Density
• Pycnocline- Layer of
rapidly changing
density due to Halo
and Thermo, acts as a
strong barrier to
mixing surface and
deep water
– Abrupt change of
temperature with
depth
https://youtu.be/TxdiU3LJlZ8
Seawater Density
• The factors that affect seawater density occur at
the surface of the ocean, salinity and
temperature changes, the surface density can
vary but the deep ocean changes very little
• Water is not compressible so deep ocean
pressures have little effect on the density
Carbon Dioxide CO2
• Carbon dioxide is one of the most abundant
gases dissolved in seawater
• Seawater can hold almost a thousand times
more CO2 than oxygen however it is quickly
used up by photosynthesis so there is usually
about 60 times more CO2 than oxygen
dissolved in sea water
Acidity and Alkalinity of Seawater
• An Acid is a compound that releases hydrogen
ions (H+) when dissolved in water.
• Alkaline or base is a compound that releases
hydroxide ion (OH-) when dissolved in water
• Water can act as both an acid or base but only
in small amount due to water molecules
dissociating and reforming
𝐻2 𝑂 ⇆ 𝐻+ + 𝑂𝐻−
The pH scale
• pH scale (potential of Hydrogen) measure of
acidity or alkalinity of a solution
• pH measures the concentration of H+
– pH = - log[H+ ]
• pH ranges from 0 (strong acid) to 14 (strong
base)
The pH scale
• pH value less than 7 = acid
• pH value greater than 7 = base (alkaline)
• pH 7 = neutral
– Pure water same amount of H+ to OH-
pH Scale
Acidity and Alkalinity of Seawater
• Water in he ocean combines with carbon dioxide to
form a weak acid, called carbonic acid (H2CO3), which
dissociated and releases hydrogen ions (H+)
𝐻2 𝑂 + 𝐶𝑂2 → 𝐻2 𝐶𝑂3 → 𝐻 + + 𝐻𝐶𝑂3 −
This reaction seems to make the water more acidic but in
fact it keeps the water slightly basic through the process
of buffering.
Acidity and Alkalinity of Seawater
Seawater too
basic drops pH
↓
Seawater too
acidic pH rises
↓
• Carbonate Buffering System of
the ocean- CO2 combines with
H2O to form carbonic acid
(H2CO3). Carbonic acid can lose
an H+ to form Bicarbonate
HCO3• The Bicarbonate can also lose
its H+ to form a Carbonate ion
(CO3-) which will combine with
Ca to form Calcium
Carbonate(CaCO3) which is
deposited on the ocean floor
Acidity and Alkalinity of Seawater
• Buffering- Calcium Carbonate can come out of solution
and the carbonate will pick the H back up to remove it
from the water
• If pH of ocean rises (too basic) it causes H2CO3 to
release H and drop pH
• If pH of ocean drops (too acidic) HCO3 combines with H
to remove it raising pH
• pH of ocean surface averages 8.1
Acidity and Alkalinity of Seawater
• Deep-ocean water contains more
carbon dioxide than surface
water because deep water is cold
and has the ability to dissolve
more gasses
• The higher pressure also helps
the dissolution of gasses
• When marine organisms with
calcium carbonate shell die and
sink to the deep ocean the
neutralized acid through
buffering
Acidity and Alkalinity of Seawater
• The ocean appear to have removed a large
amount of the atmospheric CO2 added by
fossil fuel burning during the industrial age
Acidity and Alkalinity of Seawater
• The intake of so much CO2 through time has
increase the pH of seawater. This harms
animals that use calcium carbonate to make
their outer shell like coral reefs and clams
• https://youtu.be/Wo-bHt1bOsw
Vicinal Water
Exotic Properties of Cell Water
Modified Water
• Water molecules within a cell that are touching a cell
membrane or layers close to it are modified by
solvation forces
• Water in a living cell has solutes like NaCl, potassium,
magnesium, phosphate as well as fats, proteins and
carbohydrates dissolved in it which change the
structure of water
• A cell has hundreds of surfaces, about 840 acres of
cell membrane in a single cell so more than 90% of
the water is Vicinal
Modified Water
• Vicinal water is 3% less dense, Absorbs 25% more heat,
and has greater Viscosity than nonvicinal water
• The properties of water change gradually with
increasing temperature, the properties of Vicinal water
change Abruptly at specific temperatures 59, 86, 113,
and 140 degrees F
• There is an increase of 20-30% in the ratio of potassium
to Sodium at these 4 temperatures. Healthy chemical
functioning of the cell depends on this ratio being
maintained
Modified Water
• Vicinal water change Abruptly at specific
temperatures 59, 86, 113, and 140 degrees F
• The mammalian body temperature of 98.6
degrees F falls exactly in between 86 and 113, as
far from the two as possible.
• If 122 was the normal temp between 113 and
140 too many calories would be needed to
maintain the temp
• If 72 had been chosen between 56 and 89
overheating at earths average temp of would
have been certain