Warm-up (Ch 4) 1.What is a “polar molecule”? 2.What is Cohesion? 3.What is Adhesion?

Chemical & Physical Properties of Water

Water Molecule= H 2 O 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 H 2 O 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 H 2 O temp at 0 C while absorbing heat (80 cal) Heat Capacity – ability to hold heat Latent Heat of Evaporation: –H 2 0 absorbs A LOT of heat (539 cal) energy before it evaporates, keeping the H 2 0 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.

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

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 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 CO 2 : Carbonic Acid<  Bicarbonate<  Carbonate H 2 CO 3 ( dissociates) H + HCO 3- CO 3= 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: CO 2, O 2, N 2 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 NORMAL 3-4 ppm STRESS 0-2 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 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 1 st 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/ cm 2 = 14.7 lbs/ in 2 Pressure increases 1 ATM for every 10 meters depth