the sea around us lecture 4: 23 january 14 water is the wonder substance: physical & chemical...
TRANSCRIPT
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The Sea Around UsLecture 4: 23 January 14
Water is The Wonder Substance: Physical & Chemical Properties
Drown with Me Porcupine Tree.
Thanks to Zach R.
Ocean Breathes Salty Modest Mouse
Water Cycle Jump!
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• Lecture Review Questions:
• TA Office Hours (T & W 11-12)
• On-line Assignment 2 is due tonight by 11pm
• Homework 1 is available on Angel
• Cell Phone Recycling
• Book pics! (Angel dropbox)
Thanks to Wanyu L.Read Chap. 5 of Trujillo and Thurman(on reserve in EMS Library, Deike Bld)
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• Lecture Review Questions:
• TA Office Hours (T & W 11-12)
• On-line Assignment 2 is due tonight by 11pm
• Homework 1 is available on Angel
• Cell Phone Recycling
• Book pics! (Angel dropbox)
Thanks to Sze Yu Y.Read Chap. 5 of Trujillo and Thurman(on reserve in EMS Library, Deike Bld)
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Florida couple planning for life under the sea
http://www.wtsp.com/news/science/story.aspx?storyid=169031&catid=67
World Ocean Council See link for Internship Program.
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Water Promotes Continuity of Life on EarthLow viscosity
• rapid flow to equalize pressure differencesHigh surface tension
• allows wind energy to be transmitted to sea surface• allows cells to hold shape --and life to form• controls the behavior of water drops
High heat capacity• cools/warms slowly relative to land • aids in heat retention & transport• minimizes extremes in temperature• helps to maintain uniform body temps
High latent heat of evaporation• very important in heat/water transfer in atmosphere
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Heat(cal, or Joules)
Tem
pera
ture
(°C
)
water
Heat, Temperature and Changes of PhaseWhich statement is correct about this plot?
• Ice changes to water (melts!) at 0° C
• If we add heat to water (or ice) the temperature rises, this is known as sensible heat
• Heat is required to change the phase of a substance (for example, ice to water); this is known as latent heat
Ice
05
0-5
010 50
Latent heat
Sensible heat
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Latent Heat and Changes of State
Latent heat of fusion (or melting)• Heat to form or melt ice (liquid
to solid phase)• 333 kJ/kg (80 calories/gram)
Latent heat of vaporization (or precipitation)• Heat to vaporize (boil) a liquid or
condense liquid from a gas phase• 2260 kJ/kg (540 calories/gram)
Evaporation of water from the surface can occur at any temperature. However, it takes more energy to evaporate at low T than to boil off vapor once water reaches 100°C
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Heat Capacity Heat required to change the temperature (by 1 °) of a given mass
Heat input (J/kg or cal/gram)
Liquid water
Rock & Soil
4190Kg °C
J-1 Te
mpe
ratu
re (
°C)
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Heat Capacity Heat required to change the temperature (by 1 °) of a given mass
Heat input (J/kg or cal/gram)
Tem
pera
ture
(°C
)
Liquid water
Rock & Soil
10 50
20
10
30
Pepsi
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Heat Capacity Heat required to change the temperature (by 1 °) of a given mass
Heat input (J/kg or cal/gram)
Tem
pera
ture
(°C
)
Liquid water
Rock & Soil
10 50
20
10
30
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Heat Capacity Heat required to change the temperature (by 1 °) of a given mass
Heat input (J/kg or cal/gram)
Tem
pera
ture
(°C
)
Liquid water
Rock & Soil
10 50
20
10
30
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Heat Capacity Heat required to change the temperature (by 1 °) of a given mass
Heat input (J/kg or cal/gram)
Tem
pera
ture
(°C
)
Liquid water
Rock & Soil
10 50
20
10
30
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Heat Capacity Heat required to change the temperature (by 1 °) of a given mass
Heat input (J/kg or cal/gram)
Tem
pera
ture
(°C
)
Liquid water
Rock & Soil
10 50
20
10
30
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Heat Capacity Heat required to change the temperature (by 1 °) of a given mass
Heat input (J/kg or cal/gram)
Tem
pera
ture
(°C
)
Liquid water
Rock & Soil
10 50
20
10
30
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Heat capacity and phase changes: ice (solid)
water (liquid) vapor or steam (gas)
0 200 400 600 800Heat input (cal/gram)
Tem
pera
ture
(°C
)
150
100
-100
50
0
-50
Liquid water
Ice
Vapor
Latent Heat Heat needed to change phase (from solid to liquid, liquid to gas, liquid to solid, etc.)
Latent heat of vaporization or condensation 540cal/gm
Latent heat of fusion or melting 80cal/gm
Ice + liquid
vapor+ liquid
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Clicker question:
Which is the best answer
A. Viscosity is a measure of resistance to shear motion
B. A low viscosity liquid pours more slowly than a high viscosity liquid
C. The viscosity of water is zero
D. Water is highly compressible, which means that 1 kg of it occupies a much, much smaller volume at the bottom of the ocean than near the ocean surface
E. A & D
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Consider: two identical pots, filled with equal masses of fluid, on identical burners on a stove.Pot A is filled with a fluid of low heat capacityPot B is filled with a fluid of high heat capacity
After a time…..
A. The material in Pot A has reached higher temp.
B. The material in Pot B has reached higher temp.
C. Both pots are at the same temp.
Heat Capacity is the heat required to change the temperature (by 1 °) of a given mass of material
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The high heat capacity of water means that it heats up and cools off more slowly
than land.
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Latent heat is a key factor in Hurricane development and sustainability.
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Properties of Water: Heat CapacityWhat is heat capacity? Why is it so high for H20?
Adding heat to water:• speeds up molecules • break bonds
Hence, less warming or less evaporation than expected
When heat is removed from water:• bonds form and restructure, material condenses (e.g., gas to liquid)
• energy is released via bonds formationEnergy release causes heating and thus temperature decrease is smaller than expected
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Density of Fresh Water & Ice
• Ice is less dense than water. Ice at 0 °C is 917.0 kg/m3
• Ice has an open hexagonal structure: Ice density is lower than water
Water molecular structure
Ice molecular structure
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Density of Water• Fresh water reaches maximum density at 3.98
°C• Density= 1,000 kg/m3 (1kg/liter)
• Density decreases as water is heated above 4°C
• At 20 °C, density
of pure H2O is
998.23 kg/m3
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How much heat energy is required to melt 10 grams of ice?
A. 80 caloriesB. 540 caloriesC. 800 caloriesD. 54 caloriesE. 5400 calories
0 200 400 600 800Heat input (cal/gram)
Tem
pera
ture
(°C
)
150
100
-100
50
0
-50
Liquid water
Ice
Vapor
Latent heat of evaporation 540cal/gm
Latent heat of fusion or melting 80cal/gm
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Hurricanes strengthen and gain energy by:A. Release of latent heat at high elevation within the eye, which
causes air to warm-up and riseB. Release of latent heat associated with melting of ice particles,
which makes air heavierC. Using their Lion cardD. Absorbing heat from the sunE. None of the above
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Heat capacity and phase changes: ice (solid)
water (liquid) vapor or steam (gas)
Latent Heat Heat needed to change phase (from solid to liquid, liquid to gas, liquid to solid, etc.)
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Seawater is essentially an NaCl solution
Average seawater salinity is 35 ppt (35 g/kg), but it varies from place to place
Why the Sea is Salty
37 ppt30 ppt Surface water salinity
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Why the Sea is Salty
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Why the Sea is Salty
And over the eons of time, the sea has grown ever more bitter with the salt of the continents
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Was the Chemistry of the Ancient Oceans the Same as Today?
Time (billions of yrs)O
cean
Salin
ity
35 0/00
Surface water salinity
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Note theattraction ofoppositely
charged ends ofwater moleculesfor one another
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Cl-, Na+, S04-2, Mg+2, Ca+2, K+ >99% of salt in sea water
HC03-2, Br-, Sr-2, B+2, F- (with these, 99.99%)
http://www.webelements.com/
Seawater is essentially an NaCl solution (saltwater)
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All other elements occur at very low concentrations (ppm to ppb: 10-6 to 10-9)
Seawater is essentially an NaCl solution
Average seawater salinity is 35 ppt or 35 g/kg.
Relative abundance of ions in seawater, in rank order:
Cl, Na, SO4, Mg, Ca, K (these make up >99% of the salt in seawater)
HCO3, Br, Sr, B, F (with these >99.99% of the salt in seawater)
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Charges must balance, therefore:Charge associated with cations: Na+, Mg+2, Ca+2, K+
Must equal charge associated with anions: Cl-, SO4
-2Major ions in seawater keep “constant proportion,” regardless of salinity
• Except near river outlets (near coastal regions)
• Salinity (o/oo) ~1.81 x Chlorinity (o/oo)
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Ocean Chemistry is influenced by Erosion and Weathering of the land
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For example, exchange of Magnesium (Mg) in seawater for Ca in ocean crust supplies excess Calcium
•Difference in chemical compositions between rivers and ocean
--reflects sedimentation (precipitation) processes--other inputs/exchanges, such as basalt-seawater reactions at midocean ridges
Rivers vs. Other Sources
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Oceans: Chemical Inputs-rivers (weathering)-volcanic gases: HCl, SO2, CO2
-interaction of seawater with seafloor, e.g., hot basalt associated with Hydrothermal Circulation, this is a source of Ca and K
Note: A volume of water equal to the entire ocean is circulated through seafloor material (crust) ~ every 10 m.y.
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Ocean Chemistry is influenced by:
A. By water interacting with rocks (Earth’s crust) at the mid-ocean ridges
B. Evaporation of seawater
C. River water D. Erosion and
weathering of the land
E. All of the above.