1 Lecture 8: Seawater Introduction to Oceanography Surtsey, Iceland. Wikimedia Commons, NOAA image, Public Domain, http:// commons.wikimedia.org/wiki/ File:Surtsey_eruption_2.jpg Physical and chemical properties of Seawater Playa del Rey & LAX, CA, E. Schauble, UCLA Periodic Table figure, NASA Science Education Resource Center, Public Domain
24
Embed
Introduction to Oceanography - UCLAschauble/EPSS15_Oceanography/... · 5 Heat Capacity The only common liquid with higher heat capacity than water is ammonia! Substance Heat Capacity
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
1
Lecture 8: Seawater
Introduction to Oceanography Surtsey, Iceland. Wikimedia Commons, NOAA image, Public Domain, http://commons.wikimedia.org/wiki/File:Surtsey_eruption_2.jpg
Physical and chemical properties of Seawater
Playa del Rey & LAX, CA, E. Schauble, UCLA
Periodic Table figure, NASA Science Education Resource Center, Public Domain
2
Atoms • Atom: cannot be broken down into
simpler parts by chemical means • Nucleus:
– Protons (+) & Neutrons (uncharged) – Massive – Small (~10–15 m)
• Electrons (–) – Little mass – Most of the volume
(~10–10 m = 1 Å)
HeliumSvdmolen/Jeanot, Wikimedia Commons, Creative Commons A S-A 3.0, http://commons.wikimedia.org/wiki/File:Atom.svg
Molecules • Substances made up of chemically bonded
Na+: 11p+, 10e– Elements on the left side of the periodic table of elements tend to become positive (H, Na, Mg). Elements near the right side of the periodic table tend to become negative (O, F, Cl)
E. Schauble, UCLA
3
What kind of ions will an element form?
NASA image, Science Education Resource Center, http://serc.carleton.edu/images/usingdata/nasaimages/periodic-table.gif, Public Domain
Tend to form cations (+)
Tend to form anions (–)
Chemical Bonds • Covalent: e– shared between
atoms (i.e., H2O) • Ionic: Charges borrowed by
anions – Like Na+Cl–
• Hydrogen Bonding: in water, H has slightly + charge, which attracts negatively charged O. H in water molecules also attracts anions like Cl– O in water molecules also attracts cations like Na+ Bond Strength: Covalent > Ionic > H-bond
Na+ Cl–
+
+
e–
e– e–
e– e–
e–
e–
8+
e–
e–
e–
All images E. Schauble, UCLA
4
Water Molecule: H2O Covalent bond between O and H • Polar Molecule
– Positive “ears”-105o
– Mickey Mouse – Polar structure
• Hydrogen Bonding – Effect of polarization – ~5% as strong as covalent
bonds – tends to make molecules
clump together – i.e., condense
e–
e– e–
e–
e–
e–
e–
e–
8+
e– +
e– +
O H
H
+
+
e–
e– e–
e– e–
e–
e–
8+
e–
e–
e–
E. Schauble, UCLA ball & stick model rendered using MacMolPlt
Hydrogen bonding • Hydrogen Bonding
– Each H2O: 4 possible H-bonds
– Makes liquid water “clump” together
– Accounts for many peculiarities
• Great solvent power – Saline ocean
water • Thermal and density
properties
Qwerter/Michal Maňas, Wikimedia Commons, Creative Commons A S-A 3.0, http://en.wikipedia.org/wiki/File:3D_model_hydrogen_bonds_in_water.jpg
5
Heat Capacity
The only common liquid with
higher heat capacity than
water is ammonia!
Substance Heat Capacity (cal/gram/oC)
Granite 0.20 Gasoline 0.50 Water 1.00 Ammonia 1.13
Photo by ..its.magic..,
Flickr, Creative Commons 2.0,
http://www.flickr.com/photos/rizielde/
3373257326/sizes/l/
Heat Capacity Examples:
TV dinner: Aluminum Foil vs. Gravy. Both are at the same temperature, but gravy has much higher heat capacity – it hurts!
At the beach: Sand vs.water
Photo by A. Lau, “are you gonna eat that”, http://www.flickr.com/photos/andreelau/186536202, Creative Commons Attribution-NonCommercial-NoDerivs 2.0 Generic
6
LAX -- on coast. Strong ocean
influence. Little daily/seasonal
variation in Temp.
Omaha, NE – middle of continent.
Weaker ocean influence.
Variable Temp.
Climate Comparison
Pidwirny, M. (2006). "Climate Classification and Climatic Regions of the World". Fundamentals of
GOES-9 movie, NASA Mesoscale Atmospheric Processes, Public Domain,
http://rsd.gsfc.nasa.gov/rsd/movies/preview.html
NASA image, Public Domain, Science Education Resource Center, http://serc.carleton.edu/images/usingdata/nasaimages/periodic-table.gif
Tend to form cations (+)
Tend to form anions (–)
Chemical Properties of Seawater
10
Water: Universal solvent (almost) Rule of solubility: like dissolves like
• Water is polar, so it tends to dissolve polar molecules and ionic salts• Non-polar stuff like oil not dissolved well
Oil-like (hydrophobic) parts of molecules in our cell membranes keep us from turning into puddles of bone soup.
Water dissolving salt, Liu and Michaelides, London Centre for Nanotechnology, UCL,
http://www.ucl.ac.uk/news/ucl-views/0803/salt500
Water: great at dissolving stuff • H-bonding in H2O like ions & polar molecules
Water combining with ions from sodium chloride
Based on illustrations by Steve Berg, Winona State U. Free license for educational use, http://course1.winona.edu/sberg/Illustr.htm
11
Salinity Dissolved Salts: Mainly Na+
and Cl– Constituents of table salt
No salt crystals in seawater Ions separated in seawater,
recombine on evaporation
Average ocean salinity: 3.5% by mass
Seawater: 96.5% water, 3.5% dissolved substances
4 x 1019kg dissolved salt Enough to cover the planet with a
80 m thick layer
Saltwater evaporation ponds, San Francisco Bay, CA. dro!d, Creative Commons A S-A 2.0, http://flickr.com/
photos/23688516@N00/364573572
Sources of Dissolved Salts 1) Weathering and alteration of
the crust Seawater chemistry doesn’t quite
match river water • Na, K, Mg, Ca can be derived
from rock weathering • BUT not everything can be due to
crustal weathering alone 2) Mantle degassing
(volcanoes) H2O, CO2, HCl, N2, H2S released in volcanic gases
Bottom: Halemaumau, Hawaii, Mila Zinkova, Wikimedia Commons, Creative Commons A S-A 3.0, http://upload.wikimedia.org/wikipedia/commons/9/92/Sulfur_dioxide_emissions_from_the_Halemaumau_vent_04-14-08_1.jpg
Top: Rio Tinto, Spain, Carol Stroker(?), NASA, Public Domain, http://upload.wikimedia.org/wikipedia/commons/b/b0/Rio_tinto_river_CarolStoker_NASA_Ames_Research_Center.jpg
12
Major Constituents Most abundant dissolved elements & molecules: