Transcript The Waters of the Ocean

Chapter 3
Chemical and
Physical Features
of the Oceans
Why study this?
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Part One: The Waters of the Ocean
•Water makes up 80% of
most marine organisms.
•95 % in jellyfish!
•Makes life possible!
Water: Three States
Solid
Liquid
Gas
Water is the only substance
that occurs in all 3 states
within the range of surface
temperatures on Earth.
Fig. 2.1
The Unique Nature of Pure Water
 H2O
 Covalent bonds
 Water is polar
 Allows for weak hydrogen
bonds to form between different
water molecules.
 Reason for many of waters
unique properties
Opposites attract
Fig. 2.2
The Unique Nature of Pure Water
 Molecules heated, move
quicker, bonds break until
evaporation.
 Molecules cool, move slower
 Water becomes denser as it
cools, molecules closer, same
mass, less volume.
 Freezes when molecules
locked into a fixed crystal by
hydrogen bonds.
http://www.metaphysics-for-life.com/big-bang-theory.html
Fig. 2.2
Water and Ice
 Solid water is less dense
than liquid water.
 Insulates the water
below so that it doesn’t
freeze.
 Ice forms on top allowing
organisms to live
underneath the ice
arcodiv.org
Heat Capacity
 Hydrogen bonds must be broken before molecules can
begin to move around
 Water melts at higher temperature & absorbs a lot of
heat when it melts and great deal of heat must be
removed to freeze it = high heat capacity.
Heat Capacity
 In melting ice, added heat breaks more hydrogen
bonds than increasing molecular motion, so the temp
of ice-water mixture remains at 0°
 Adding heat goes into melting the ice not raising
temperature. Ex: Ice keeping drinks cold
 High heat capacity, therefore marine organisms not
affected by temperature changes in atmosphere
Fig. 2.2
Heat and Water
Molecular structure changes with temp.
1) In ice, H bonds hold molecules in a hexagonal pattern, in a
crystal
2) Heat added, ice warms up, molecules move quicker until
break free of crystal structure. Ice melting
3) While ice is melting, added heat absorbed by H bonds, not
by increasing the temp.
4) When ice completely melted, additional heat causes temp
to rise.
5)Some molecules fast enough to break all bonds and
evaporate.
arcodiv.org
At 100 degrees C, all h bonds broken, water boils and
evaporates.
Fig. 3.3
Fig. 2.2
Water as a
Solvent
 Dissolves more things
than any other natural
substance, esp. salts
 called the universal
solvent
 Salts made of opposite
charged particles (ions)
and conduct electricity
wat
Fig. 2.2
Water as a
Solvent
 In water, strong ion
charges attract water
molecule, water molecules
surround the ions and pull
them apart =dissociation
 Dissociation Video
wat
Water as a Solvent
-Seawater
 Characteristics of
seawater due to nature
of pure water and
materials dissolved in it
 Dissolved solids due to
weathering of rocks on
land & hydrothermal
vents
 Rain and snow
Water as a Solvent
-Seawater
 Sodium chloride account for
85% of all solids dissolved,
Na and Cl
 Salinity is total salt
dissolved in seawater
 Measurement
 Parts per thousand, 30-35
 g/mL, 1.020-1.025
Challenger Expedition
• William
Dittmar
•Wrote papers on
composition of seawater
Rule of constant proportions
•salinity varies, but not
percent composition of ions
Seawater
 Removal and addition of
water, changes salinity.
 How?
 Avg. 35 ppt and between
33-37 ppt in open ocean.
Salinity fluctuations
•Oceans well mixed, salinity varies as a result of
addition/removal of fresh water, rather than
removal/addition of salt.
Salinity, temperature, and density
 Get denser as it gets saltier, colder, or both
 Ocean temp varies -2° to 30°C (28-86°F)
 Temps below 0°C possible because saltwater freezes at
colder temps.
 Density controlled more by temperature than salinity
 Are exceptions therefore salinity & temp need to be
measured to determine density
Trace Elements and Dissolved gases
 Trace elements: Nitrogen Phosphorus, and Iron
 Needed to make amino acids, nucleic acids
(DNA)
 Sulfate, Magnesium, Calcium, Potassium,
Bromide, Bicarbonate, Fluoride
 O2, CO2 and N2 in atmosphere and sea surface
 Gas exchange happens between the surface and
atmosphere
Trace Elements and Dissolved gases
 Oxygen
 Necessary for respiration
 Most oxygen is released into the atmosphere
 Carbon Dioxide
 Necessary for photosynthesis
 80% of gasses is carbon dioxide
 50 times more CO2 stored in oceans than in
atmos.
 Important topic in global climate change
 Gas dissolves better in colder water
Transparency
 Sunlight can penetrate,
but it’s affected by the
material suspended in
the water
 Important to the
photosynthetic
organisms
Transparency
 Seawater is transparent, but not all colors penetrate as
well.
 blue is best, red is worst
Transparency
 Runoff
 makes coastal waters less
transparent than open
ocean.
 Plankton and algae blooms
can affect water transparency
 Simple instrument to test
water clarity, Secchi disk
Pressure
•Sea level = 1 atm or 14.7
pounds per square inch (psi)
•On land, organisms are
under 1 atm.
• Marine organism have the
pressure of the atmosphere
and water
Pressure
•Added weight of water
column
•Each 10 meters (33 ft) =
another atmosphere
Ex: 33 ft down =
_____ atm of pressure.
Ex: 66 ft down =
______atm of pressure.
Pressure Effects
•Increase pressure/depth, gases compress.
•Causes gas-filled structures to shrink or collapse
•Decrease pressure/depth, gases expand
Head in middle taken to 2000 ft, head
on left taken to 3000 ft