Water & Ocean Structure Ch. 6
Wonderful Water 70% of Earth covered in H 2 O 70% of your body is H 2 O You die in ~3-5 days without H 2 O Regulates Coastal Temperatures
What is Water? Matter: has mass, takes up space Matter made up of 92 elements Water = 2 H + O (H 2 O)
(+) (no charge) ( ) Atoms = smallest units of an element nucleus Atoms made up of smaller particles: Protons, Neutrons, Electrons
Ions Neutral atoms have the same number of electrons as protons Ions: atoms with uneven numbers of electrons & protons electrically charged Positive ion: more protons (+) than electrons (Na + ) Negative ion: more electrons ( ) than protons (Cl - )
Atoms bond together to form molecules Compounds = bonds of different atoms Covalent bond: Atoms share electrons to become more stable Molecules
Atoms with more than one shell are most stable w/ 8 electrons in outer shell
1 electron each 6 electrons (outer shell) H 2 O = Polar molecule 105 bend 8 electrons (+) side ( ) side
Water - Polar Molecule Having both a (+) & ( ) side: Water acts like an electromagnet (+) side attracts ( ) ions or ( ) end of other polar molecules ( ) side attracts (+) ions or (+) end of other polar molecules Water does this so well, it s able to dissolve many substances Universal Solvent
Hydrogen bonds Polar nature of H 2 O: It s attracted to other H 2 O molecules (+) Hydrogen is attracted to ( ) oxygen
Properties of Water 1. Cohesion: H 2 O molecules stick together (H+ bonding) surface tension Water Strider Walks on Skin 2. Adhesion: Attraction of water to other molecules capillary action: why your towel gets wet
3. High Heat Capacity: Measure of Heat required to raise the temp. of 1 gram of a substance by 1 C (1.8 F) Heat: Energy (kinetic) produced by vibrations of atoms or molecules
Vibrate weakly, rigidly held in place Vibrate more rapidly, move freely & farther apart Highly energetic, move far apart Ice Water Vapor
3. High Heat Capacity: It resists changing temperature when heat is added or removed Highest of any liquid or solid (<ammonia) Hydrogen bonds: a lot of heat must be added to speed up H 2 O molecule movement & thus raise its temp. EX: boil water, Hot sand & cool ocean
Ocean Moderates World Climate Ocean absorbs a lot of heat Ocean varies in temperature much less than land Avg. Temp. Ranges Ocean: 2 to 35 C Land: 70 to 57 C
4. Water occurs in 3 states: Solid, Liquid, Gas (vapor) Only substance on Earth (naturally occurring) Resists changes of state = energy input or removal required
5. High Latent Heat of Fusion Heat removal required to change water from liquid to solid (ice) Freezing Point: Temperature at which a liquid becomes a solid Water = 0 C Ice Floats!
Why Does Ice Float? Ice is less dense than water Density: Mass (wt.) of a substance per unit volume Number of molecules packed into a volume of space For most substances Density with temp. (molecules closer together) NOT WATER ICE!
As temp., H2O molecules vibrate less At freezing point, packed less efficiently (crystal lattice) less dense than liquid water Packed as tightly as they will go If temp. is lowered, molecules push back harder Repel each other Ice 24 solid molec. = 27 liquid molec.
No Polar Bears! Real snowflake crystal! Imagine a world where ice sank instead of floating No ice skating!
6. High Latent Heat of Vaporization Heat needed to change water from liquid to gas Highest of any substance Energy required to break strong Hydrogen bonds Water remains a liquid on most of Earth
Ocean Currents help to move water around Earth Warm water at equator (greater solar heating) Cold water at poles
Temp ( F) Temp ( C)
Unique Properties of Seawater 96.5% pure H 2 O, 3.5% dissolved solids & gases Presence of solids (salts NaCl): Lowers the freezing point Increases density
Density as temperature & salinity
Density & Stratification Seawater can become layered (stratified) b/c of differences in density: Surface (2% total ocean volume) Pycnocline (Mid Layer 18%) Deep Zone (80%)
Surface: Well mixed (wind, currents), Least dense (Less salty, Warm) Pycnocline: Area of rapidly changing density (colder, more salty) Rain, FW runoff Cold, Dense, Salty Deep Zone: Little change in density with depth (temp. & salinity stabilize)
Pycnocline: Traps cold, dense salty water at depths 80% of seawater in deep sea Deep-water upwelling brings some of this water to the surface
Light in the Ocean Light bends (refracts) as it enters water: Light travels more slowly in water than in air Electromagnetic Radiation Light is quickly scattered or absorbed by gases, particles, organisms
Ocean is divided into 2 zones based on the amount of light received: 1. Photic Zone (sunlit): Nearest surface Enough light penetrates water to support photosynthesis >90% of marine life lives here
2. Aphotic Zone: 90% percent of ocean No light Cold, high pressure No photosynthesis Animals eat detritus from above OR Chemosynthesis (Hydrothermal vent bacteria) Bioluminescent organisms make their own light Twilight zone
Many marine organisms use sound to see in the ocean Sound waves travel much father through water than light Echolocation (sonar): locate objects (size, shape, inorganic or living) By echoes received back from their own emitted sounds
(Temperate & Polar zones) (Tropics)