Warm-up (Ch 4)1. What is a “polar molecule”?

2. What is Cohesion?

3. What is Adhesion?

Chemical & PhysicalProperties of Water

Water Molecule= H2O• Compound held together by

COVALENT bonds (VERY Strong)

Water is a POLAR molecule: Slightly negatively charged at the Oxygen end, and

slightly positively charged at both Hydrogen ends

• Many water molecules are joined together by weak HYDROGEN bonds, which form

between the POLAR molecules!

Surface Tension- “skinlike” surface. Strength determined by number of H bonds… more bonds = stronger surface tension.

• Surface Tension is stronger at colder temperatures.

• Surface Tension allows for:1) COHESION = attraction between like

substances; Ex. Water-water

2) ADHESION = attraction between un-alike substances;

Ex. Water and glass.

Viscosity: Tendency of a fluid to resist flow

• Viscosity increases as Temperature Decreases (gets colder)

• Important Effect on–Neuston (float on top of water)–Plankton (don’t sink as rapidly)–Nekton (use more energy to swim

thru more Viscous water

Three States of Water:• Occurs Naturally in 3 States on Earth• 1) Liquid – H Bonds break & re-form easily• 2) Solid – H Bonds form & hold (0 C or 32 F)• 3) Gas – H Bonds break & H2O molecules are

released into atmosphere- Evaporation (100C or 212 F)

• As temperature increases, the speed of H2O molecular movement increases, which decreases the number of H Bonds formed… causing a decrease in water density

Density (D) = mass (m)/ volume (v)• As water gets colder & colder, it becomes

increasingly more dense, and begins to FALL down through the water column….. UNTIL the temperature reaches….

• 4 C, FRESH water reaches its MAXIMUM Density, and below 4 C, water begins to form ice crystals (increasing the Volume) and becomes LESS dense!

Random H bonds in Liquid Water, break & reform

Therefore………….

ICE FLOATS!!!!!!

• Floating Ice acts as a THERMAL Blanket to the Underlying water, protecting it and allowing it to remain LIQUID !

Salt Water & Ice• Temperature at which salt

water freezes depends upon its SALINITY.

• SALT decreases its freezing point!!!!

• Therefore, salt water’s Maximum Density is right before it freezes.

Warm-up (Ch 4)1. What is the formula for Density?

2. How do temperature and salinity affect seawater density?

3. What factors affect seawater’s pH?

• Latent Heat of Melting :– Ice is able to absorb A LOT of heat

energy (which breaks up the H Bonds) before the ice melts, keeping the H2O temp at 0 C while absorbing heat (80 cal)

• Heat Capacity – ability to hold heat

• Latent Heat of Evaporation:– H20 absorbs A LOT of heat (539 cal)

energy before it evaporates, keeping the H20 temp at 100 C

Physical Characteristics of Water• Water is the Universal Solvent –

dissociates salts. –Ocean water got salts from thermal

vents & weathering rocks when Oceans formed.

–Primary Solutes are sodium (Na) and chlorine (Cl) …85% of solutes in Ocean

–Other solutes: Mg, S, Ca, K, Br …..

1)Salinity- physical factor that measures the total amount of salt (ions) dissolved

in water.• Expressed as parts per thousand or

ppt and written o/oo• Rule of Constant Proportion:

–Relative concentration of all the ions does not change in the World’s oceans.

–Ex. Red Sea 44 ppt –Ex. Baltic Sea 7 ppt

Factors Affecting Salinity:• Run-off:

–Decreases salinity• Precipitation:

–Decreases salinity• Evaporation:

–Increases salinity• Freezing:

–Increases salinity

Ocean’s Average Salinity Values

Halocline• A sharp change in salinity at a

particular depth.

http://www.cave-exploration.com/caveformation/photos/tankshalocline.jpg

Addition & Removal of Salt from Ocean• Salts Added to Ocean by

–Run-off–Hydrothermal Vent Releases

• Salt Removed from Ocean–Adhere to particles that fall to ocean floor & are buried!

2)Temperature = Range (0C to 30C)• Density= mass/volume• 2 Factors most affect Density of Seas:

– Salinity• As Salinity increases, Density increases

– Temperature• As Temperature increases, Density decreases

TEMPERATURE AFFECTS DENSITY OF SEAS MORE THAN SALINITY, BECAUSE TEMPERATURES FLUCTUATE MORE THAN SALINITY.

Thermocline• Thin, distinct layer within a large body of

water (ocean, lake) where the temperature changes more rapidly with depth than the layers above it.

• Seasonal Thermocline- in Epipelagic, easily disrupted

• MAIN Thermocline – in Mesopelagic, stable• Pycnocline- sharp change in density with

depth.• Isocline- NO change with depth

http://coexploration.org/bermuda/assets/images/thermocline.jpg

Global Climate Change• Green House Gases

–CO2, Methane, Water vapor–Trap HEAT

• Most HEAT transferred into the atmosphere from EARTH –Evaporation of OCEAN water

3) pH – measure of H+ concentration

Average Ocean = pH 7.5-8.0

OH- ions

H+ OH- balanced

H+ ions

Factors Affecting pH :• Acid Rain, Farm Run-off, Chemical

Pollutants from Industry and Agriculture

• BUFFER SYSTEM of Ocean protects pH using CO2:

• Carbonic Acid<Bicarbonate<Carbonate H2CO3 (dissociates) H+ HCO3- CO3=

takes xcess –OH takes xcess H+

Importance of maintaining stable pH

• pH affects ALL Life Processes:–Growth of organisms–Enzyme activity–Metabolism

Warm-UP• Define the following terms in your

notebooks:–Oxygen Minimum Layer–Turbidity–Pressure

4) Dissolved Nutrients – Nitrates & Phosphates act as “fertilizers” of the Seas• Bottom of Ocean is RICH with

decaying nutrients• UPWELLING brings nutrients to

surface where phytoplankton use it–COLD water falls, displacing bottom

waters, pushing them to the surface–WINDS pull water from depths

Carbon Compensation Depth (CCD)

• Depth at which the rate of dissolution of calcium carbonate equals the rate of precipitation of calcium carbonate.

• Calcium used to make shell & bones of organisms!

5) Dissolved Gases – Dissolve better in COLD waters

• Three most important gases: CO2, O2, N2

CO2 is most soluble in water, then O2, then N2

• Oxygen enters Oceans by:– Atmospheric Diffusion– Photosynthesis

• Oxygen is removed from Ocean by:– Respiration– Decomposition

Low Oxygen Levels may be Due to :• High Fish Population• Decaying organic matter• Pollutants (sewage, fertilizers)

Dissolved Oxygen (DO) levels measured in Parts Per Million (ppm):5-6 ppm NORMAL3-4 ppm STRESS0-2 ppm LETHAL

Oxygen Minimum Layer• A vertical zone in the water column

where the concentration of dissolved oxygen gas is lower than the water above and below it; usually between 400-800 meter deep

• Due to No Photosynthesis & LOTS of Decomposition

• Lower layer has less Decomposition so O2 level increases slightly

6) Transparency (Turbidity):• Visibility of water• Visible Light absorbed by water:

–Red absorbed in 1st 5 meters–Blue last to be absorbed

• Increased Turbidity due to:–Sediments–Dissolved Organic Matter–Over abundance of Plankton (Bloom)

Turbidity Measured at Sea with Secchi Disk

Problems due to Increased Turbidity:

• Suffocation of Grasses• Blocks sunlight …decreases

photosynthesis• Destroys Benthic Habitat of

Organisms• Kills Fish

7) Pressure• Increases with increased Depth• Sea Level is 1 Atmosphere (1 ATM) =

1kg/ cm2 = 14.7 lbs/ in2

• Pressure increases 1 ATM for every 10 meters depth