Oceans are filled with ???
WATER!!!!!
Let’s understand water then.
The Water Molecule
•  ‘V’-shaped molecule: 105º angle
between H nuclei –  Due to covalent bonds involving
Oxygen’s p-orbitals –  P-orbitals are 90º apart, but the
hydrogen nuclei repel each other
(Born repulsion) resulting in 105º
between hydrogen nuclei
•  Polar molecule: –  Electronegativity of Oxygen pulls
electrons away from Hydrogen
nuclei
–  Electron cloud around Oxygen
results in negative charge at the
Oxygen side and positive charge at
the Hydrogen side of the molecule • 
Polar property leads to hydrogen
bonding…
Hydrogen Bonding between Polar Molecules:
•  Hydrogen bonds
–  positive H ends attract negative
O ends into a weak bond
–  Water molecules thus stick
together
•  The polar water molecule and
resulting hydrogen bonds are
responsible for ALL of water’s
REMARKABLE properties!
•  E.g. Surface Tension
• 
–  Highest among common liquids
–  Water forms drops!
Other strange properties resulting
from Hydrogen Bonds,
–  large heat capacity, –  large latent heats of fusion and
vaporization,
–  Strange Density variations
1
Freezing & Density: Ice floats!
• 
Freezing = removal of heat, –  Slows vibrations (lowers Temperature)
–  Structure becomes ‘compact’ - increase density
Read pp. 302-305
• 
• 
Max density 1g/cc at 4ºC
Below 4ºC –  rigid framework develops (0.99g/cc 0ºC)
–  Ice - expanded structure: 105º to 109º
–  0.92 g/cc at 0ºC
Phases of Water:
•  Boiling point and freezing point are in ‘normal’ range of
temperature! –  Thus, water is present nearly ‘everywhere’
–  No other substance is present in all phases on Earth’s surface!
•  Phase Changes - change P and T (condensation, sublimation, boiling)
Heat & Phase Changes:
•  The Calorie is the unit of measure of Heat Energy
•  Definition of a Calorie: Heat required to raise 1 gram of H2O
by 1ºC
–  The more water you have, the more heat energy is required to raise T!
•  Temperature is not heat!
–  Heat = Energy. This energy causes molecules to vibrate. •  The vigor of the vibration is dependent on the number of molecules present. •  The more heat you add, the faster the molecules will vibrate.
•  The more molecules you have vibrating, the more heat energy in the system.
–  Temp ~ how fast molecules are vibrating •  Temperature does not depend on or account for the number of molecules.
2
Which contains more heat?
A. Candle flame
B. Warm Bath
Heat Capacity = amount of heat required to raise
Temperature of a substance 1ºC (this is a definition!)
•  Heat Capacity of Water = 1 calorie/mole/ºC (notice this is the definition of calorie)
–  Highest of all common solids & liquids!
–  Hydrogen boding of water causes this LARGE heat capacity
•  need lots of heat energy to vibrate all those hydrogen bonds and raise temperature!
• 
• 
• 
–  Note to science majors: the heat capacity per gram of substance is the Specific
Heat
Heat Capacity of water > most solids (20 x that of quartz)
Few liquids have greater Heat Capacity - e.g. ammonia
Examples: water vs. ethyl alcohol
–  Water vs. Ethyl alcohol
•  Ethyl alcohol’s Heat Capacity = 1/3 calorie
–  Quartz sand (beach) vs. water Heat Capacity of quartz = 0.2 cal
Big Point about Heat Capacity:
•  Water has very high Heat Capacity. Thus it takes a great amount of heat
exchange to change water’s temperature.
•  So, oceans RESISTS changes in Temperature while absorbing or releasing heat
from the Sun.
–  Compared to continents, Oceans require more heat to change temperature!
–  Therefore, little to no wide diurnal or seasonal variations in ocean temperature.
–  THUS vast amounts of Heat are moved around the globe as oceans circulate!
Which is to say…
• Oceans store & transport lots of heat!
• Thus, oceans control Earth’s heat budget
3
Heat flow and how oceans regulate climate:
•  Clausius taught us that heat flows down a temperature gradient
–  Analogy: balls roll down hill under force of gravity
–  Heat flows from hot to cold under the ‘force of entropy’ (dQ = T/dS)
• 
Oceans have high heat capacity compared to continents –  Thus, no great change in temperature of oceans relative to the continents
• 
• 
Continental temperature difference ~ 140ºC
–  N.Africa ~50ºC, Antarctic ~-90ºC
Oceanic temperature difference ~ 34ºC
–  Tropics ~ 34ºC, Arctic ~-2ºC
–  The “lake Effect” or the Thermostatic Effect of Oceans
• 
• 
During winter, oceans are warmer than continents and heat is transferred to the continents
During summer, oceans are cooler than continents and heat is transferred to the oceans
• 
The Sun’s heat warms oceans unevenly - warm tropics, cool high latitudes
• 
How does water transfer heat? See discussion of Latent Heat
–  This causes convection currents
–  How much heat is transferred (by convection!)? Review: What is Heat Capacity
A.  A Measure of Energy
B.  The capacity of a substance to radiate heat
C.  The amount of heat needed to change the temperature of a
substance
Review: The high heat capacity of water allows _____.
A. 
B. 
C. 
D. 
Water to transport great quantities of heat
Water to store great quantities of heat
Oceans to regulate climate
All of the above
4
Which way does heat flow?
A.  The baby will boil
B.  The candle will cool
C.  Cannot know
What happens in a phase change?
•  Melting ice: –  Ice crystals have ‘long-range’ order to the arrangement of molecules
–  Adding Heat vibrates the structure and disrupts this order = melting to water
–  Liquid water has ‘v. short-range’ order
•  Boil water: –  Adding Heat vibrates hydrogen bonds and disrupt order, super energetic
molecules ‘escape’ to vapor
–  Vapor has no order - individual molecules rocketing through the atmosphere
Latent Heat & Phase Changes:
Cartoon
•  What is Latent Heat? E required to melt or boil
•  Consider icy cool lemonade…
–  Initially 0ºC, as ice melts what is the Temp?
–  Latent heat fusion = Heat consumed during melting of ice
•  The latent heat of fusion of water = 80 cal/g ice
•  Add latent heat to melt ice, remove latent heat to freeze water.
5
Water’s Latent Heat of Fusion = 80 cal/g
•  Water’s Latent Heat of Fusion is quite large –  Heat required to melt ice
–  Also, Heat liberated during freezing!
–  Highest among all common solids/liquids!
Water’s Latent Heat of Vaporization = 540 cal/g
•  Water’s Latent Heat Vaporization is HUGE
–  Heat require to turn liquid at 100ºC into vapor
•  Water’s Latent Heat Evaporation = 585 cal/g –  Heat require to turn liquid < 100ºC into vapor
–  Liberated molecule must ‘take’ heat energy from surrounding
water molecules - thus the cooling effect of evaporation.
–  This is also the Heat liberated during condensation
–  Highest of all common substances - VERY IMPORTANT to
ocean/atmosphere
Zeer Pot
Nigerian
invention uses
LHE to
refrigerate
food
When water condenses
in the atmosphere to
form rain or clouds…..
A.  Heat is transferred to the atmosphere,
supplying energy for circulation of the
atmosphere.
B.  Heat is transferred to the water, which
falls back to the oceans, supplying
energy for currents to circulate.
C.  Heat is transferred to the continents,
warming them and making high
latitudes habitable.
6
Thermostatic effects of water’s latent heat
• 
Evaporation and condensation on a global scale cools the oceans
and warms the atmosphere –  at low latitude evaporation removes heat from ocean (cools tropical
seas) –  At high latitude condensation releases heat to to the atmosphere
(warming)!
Heat stored/released by sea ice:
•  Annual ice volume change: ~18,000 km3
•  How much heat is exchanged?
–  ~1.44 x1021 calories absorbed during melting!
–  ~1.44 x1021 calories liberated during freezing!
Heat transported by Gulf Stream
•  Gulf Stream outflow is 10ºC warmer than
return flow.
–  Flow is 55 x 106 m3 per second
–  Calculate 550 trillion calories per second!
•  Ocean to Atmospheric transfer of heat is even
greater!
–  Recall Latent heat of evaporation is very large.
7
Convection in the Oceans- !
Cooling of surface water at high latitude!
Warming of surface water at low latitude
North Atlantic
Cooling
Equator
Heating
We will return to this latter in the semester…
Review Questions
•  What single feature of water is responsible for some of its
important properties (e.g., high heat capacity)?
•  Which ‘direction’ does heat flow during melting of ice,
crystallization of ice, evaporation of water and
condensation of water?
•  How do the oceans influence climate?
8