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Basic chemistry○ Atomic structure
Nucleus = protons (positive) + neutrons (neutral)
http://www.rstp.uwaterloo.ca/manual/matter/graphic/atom.jpg
Chemical bonds Attractive force that holds atoms together Three major types
○ Ionic bonds ○ Covalent bonds○ Hydrogen bonds
○ Ionic bonds – weak bonds Atoms “exchange” electrons fill outer shell
- becomes positive ion if lose electron - becomes negative ion if gain electron - + & – ions attracted to each other
Na & Cl Na+ + Cl-
http://www.physicalgeography.net/fundamentals/images http://www.msnucleus.org/
membership/html/k-6/rc/minerals/3
Covalent bonds – strong bonds Atoms “share” electrons to fill outer shell H (hydrogen) has one electron, needs 1 more O (oxygen) has 6 electrons in outer shell, needs two
electrons Therefore, oxygen and 2 hydrogens bond to form water
Covalent bonds are stronger because there is sharing of the electrons
http://ghs.gresham.k12.or.us/science/ps/sci/ibbio/chem/notes/chpt2
http://www.theochem.ruhr-uni-bochum.de/~axel.kohlmeyer/cpmd-vmd
Polarity of covalent bonds○ Nonpolar covalent – electrons are shared
equally ○ Polar covalent - electrons not equally
distributed in molecule○ Water is a dipolar molecule (two polar covalent
bonds)
O strongly attracts electrons slightly negative
H slightly positive- Think of oxygen as being the “bully” – it’s larger so it pulls the
electrons towards it’s nucleus more often
○ Allows formation of H-bonding between water molecules
H2O molecule One hydrogen H and two oxygen O
atoms bonded by sharing electrons Both H atoms on same side of O atom Dipolar covalent bondDipolar covalent bond
Hydrogen bonding Polarity
small negative charge at O end
small positive charge at H end
Attraction between + and – ends of water molecules to each other or other ions
Happens because of the polar covalent bond
Fig. 5.3
Hydrogen bonding and water Hydrogen bonds are
weaker than covalent bonds but still strong enough to result in unique properties of water Cohesion = sticks to
other water molecules Adhesion = sticks to
other types of molecules High surface tension
http://faculty.uca.edu/~benw/biol1400
http://ucsu.colorado.edu/~meiercl/photography
Hydrogen bonding and waterH-bonds absorb red
light, reflect blue light blue color
High solubility of chemical compounds in water
Solid, liquid, gas at Earth’s surface
Unusual thermal properties
Unusual density
http://www.pacific-promotion.com.fr/Phototek
Unusual thermal properties of H2O H2O has high boiling
point H2O has high freezing
point
Most H2O is in liquid form of water on Earth’s surface VERY important for life
http://www.magnet.fsu.edu/education/tutorials/magnetacademy/superconductivity101/images/superconductivity-temperature.jpg
Unusual thermal properties of H2O
Water high heat capacity (specific heat capacity (specific heat)heat)Amount of heat required to raise
temperature of 1 gram of any substance 1o C
Water can take in/lose lots of heat without changing temperature – must break H-bonds
On the other hand, rocks have low heat capacity○ Rocks quickly change temperature as they
gain/lose heat
Global thermostatic effects Moderates temperature on Earth’s
surface – water temp less variable and less extreme than air temperaturesEquatorial oceans (hot) don’t boilPolar oceans (cold) don’t freeze solid
Global thermostatic effects Marine effectMarine effect
Oceans moderate temperature changes day/night; different seasons
Continental effectContinental effectLand areas have greater range of temperatures
day/night and during different seasons
Look at the differences between coastal Florida compared to Orlando
Density of water Density of water
increases as temperature decreases down to 4oC
From 4oC to 0oC density of water decreases as temperature decreases
Density of ice is less than density of water http://www.grow.arizona.edu/img/water
Density of water Dissolved solids reduce
freezing point of waterAs water freezes, the
crystalline structure “pushes out” much of the dissolved solids
Creates icy “slush” and surrounding waters become saltier
Putting salt on icy roads melts ice○ Salt lowers freezing point
of water on roads allowing it to remain liquid at colder temps
http://www.ibarron.net/users/robert/pics/2003/Norway/OsloFjord11.jpg
Water = Life• Summary:
• Unique properties of water that make life possible• High heat capacity and specific heat
• Moderates climates• Keeps equatorial regions from boiling and pole regions from
freezing solid• High latent heat – when undergoing change of state, large amount
of heat is absorbed or released• Sweat evaporating from your skin draws heat from your body,
keep you cool• Ice is less dense than liquid water• Cohesion
• Water moving up xylem in plants• Surface tension – allows plankton to stay near surface of water
Salinity Six elements make up
99% of dissolved solids in seawater – from erosion of land, volcanism
Total amount of solid material dissolved in water- Traditional definition
Typical salinity is 3.5% or 35o/oo o/oo or parts per thousand (ppt) =
grams of salt per kilogram of water (g/Kg )
Adding salts changes many properties of water
Fig. 5.12
Salinity variations
Open ocean salinity 33 to 38 o/oo However, coastal areas salinity varies
more widelyInflux of freshwater lowers salinity or creates
brackishbrackish conditionsGreater rate of evaporation raises salinity or
creates hypersalinehypersaline conditions Salinity may vary with seasons (dry/rain)
Deep ocean variation of salinity
Surface ocean salinity is variable
○ Due to occurrences at surface – rain, evaporation, etc
Deeper ocean salinity is nearly the same (polar source regions for deeper ocean water)
HaloclineHalocline, rapid change of salinity with depth
pH – Acidity and alkalinity Acid releases H+ when
dissolved in water (HCl, H2SO4)
Alkaline (or base) releases OH- (NaOH)
pH scale measures the hydrogen ion concentrationLow pH value, acidHigh pH value, alkaline (basic)pH 7 = neutral
http://www3.oes.edu/ms/science6/Pictures%20of%20Science%20Concepts/pH%20Scale.gif
Oceans absorb carbon dioxide from the atmosphere○ How do humans put excess CO2 in atmosphere?
CO2 reacts with seawater to form carbonic acidReleases H+ , decreasing pH
The additional H+ bind to carbonate ions to form bicarbonate
○ Less carbonate in the water makes it difficult for corals, mollusks, echinoderms, calcareous algae, etc. to form calcium carbonate
Ocean Acidification
Ocean water is basic – pH ~8.1○ Surface waters have already absorbed
enough CO2 to experience a pH decrease of 0.1 since pre-industrial times
- May not seem like a lot but remember that pH is measured on a logarithmic scale so that represents a 30% drop in a relatively short time period
Density of seawater 1.022 to 1.030 g/cm3 surface seawater Saltwater more dense than pure water
That is why you can float better in saltwater
Ocean layered according to density Density seawater controlled by
temperature, salinity, and pressureMost important influence is temperatureDensity increases with decreasing
temperature
Density of seawater Overall, temp has greatest
effect on density However, salinity greatest
influence on density in polar oceans polar ocean is isothermal
(same temperature as depth increases)
Currents from lower latitudes bring higher salinity water into polar areas
But polar waters are overall isothermal AND isopycnal
http://www.waterencyclopedia.com/images/wsci_03_img0394.jpg
Density versus depth
PycnoclinePycnocline, abrupt change of density with depth
ThermoclineThermocline, abrupt change of temperature with depth
Density differences cause a layered ocean
Mixed surface water Pycnocline and thermocline Deep water
Misconceptions Increases in global temperatures in the
atmosphere and the consequent warming of the oceans will only create a problem for people living along the coast.
Water exists in the ground in actual rivers or lakes that are constantly renewed.
People drink bottle water because it is better for our health; the safety of tap water is below consumption standards.
Ocean Literacy Principles 1e - Most of Earth’s water (97%) is in the ocean. Seawater has unique properties: it is saline, its
freezing point is slightly lower than fresh water, its density is slightly higher, its electrical conductivity is much higher, and it is slightly basic. The salt in seawater comes from eroding land, volcanic emissions, reactions at the seafloor, and atmospheric deposition.
1g - The ocean is connected to major lakes, watersheds and waterways because all major watersheds on Earth drain to the ocean. Rivers and streams transport nutrients, salts, sediments and pollutants from watersheds to estuaries and to the ocean.
3a - The ocean controls weather and climate by dominating the Earth’s energy, water and carbon systems.
Sunshine State Standards SC.6.E.7.1 Differentiate among radiation, conduction, and convection, the three mechanisms by
which heat is transferred through Earth's system. SC.6.E.7.6 Differentiate between weather and climate. SC.8.P.8.1 Explore the scientific theory of atoms (also known as atomic theory) by using models to
explain the motion of particles in solids, liquids, and gases. SC.8.P.8.4 Classify and compare substances on the basis of characteristic physical properties that
can be demonstrated or measured; for example, density, thermal or electrical conductivity, solubility, magnetic properties, melting and boiling points, and know that these properties are independent of the amount of the sample.
SC.8.P.8.6 Recognize that elements are grouped in the periodic table according to similarities of their properties.
SC.8.P.8.8 Identify basic examples of and compare and classify the properties of compounds, including acids, bases, and salts.
SC.912.E.7.9 Cite evidence that the ocean has had a significant influence on climate change by absorbing, storing, and moving heat, carbon, and water.
SC.912.P.8.4 Explore the scientific theory of atoms (also known as atomic theory) by describing the structure of atoms in terms of protons, neutrons and electrons, and differentiate among these particles in terms of their mass, electrical charges and locations within the atom
SC.912.P.8.5 Relate properties of atoms and their position in the periodic table to the arrangement of their electrons.