The Nature of Water Compare and contrast the general structures of plant and animal cells. Compare and contrast the general structures of prokaryotic and eukaryotic cells.

The Ocean Planet Human View: – Is there enough water? * Sea Life View?

Marine Life Point of View 71% is only the surface area Consider Volume & Depth: – Oceans are 99% of the Biosphere *Why wouldn’t much of the atmosphere be considered part of the biosphere?

Ocean Averages 3,730m (12,238 ft) deep Deepest Point: Challenger Deep in Mariana Trench- 10,838m (35, 558ft) deep

Hydrologic Cycle

The Polar Molecule H2O: Hydrogen bonds to Oxygen by covalent bond Polar Molecule: positively and negatively charged ends Dipolar: 2 positive poles

Polar Molecule (Con’t) Hydrogen bond: + H meets – O – Individually weak – Strength in numbers – Give Water Unique Properties

Effects of Hydrogen Bonds 1. Liquid at room temperature 2. Cohesion: water molecules stick together 3. Adhesion: water sticks to other materials

Effects (continued) 4. Viscosity: tendency for a liquid to resist flow – Water cools- viscosity rises – 20 degree drop in temperature increases water’s viscosity by 60% – Affect energy aquatic organisms expend

Effects (continued) 5. Surface Tension: water’s resistance to objects attempting to penetrate its surface – Cohesion makes it possible – Organisms rest on surface tension – Scientists: gas exchange between ocean & atmosphere

Why does Ice Float? Ice Floats: Ice is less dense than liquid water – H bonds spread the molecules into crystal structure – Taking up more space

Ice (continued) How does it affect the planet? – If ice sank: frozen oceans – Colder Climate

Solutions & Mixtures in Water Solution: molecules of 1 substance are homogeneously dispersed among the molecules of another substance Mixture: 2 or more substances closely intermingle, but retain their individual characteristics

Water as a Solvent Example- how salt dissolves – Water polar characteristics pull apart NaCl crystal – Negative O end attracts Na+ – Positive H end attracts Cl-

Solvent (continued) Nonionic: Sugar crystals in water *Water is the Universal Solvent!

Salts & Salinity *Salinity- the total concentration of all dissolved inorganic ions (NaCl & everything else: dissolved salts) *Oceans Average Salinity= 35ppt or 3.5%

Colligative Properties of Seawater Colligative Properties: Properties of a liquid that may be altered by the presence of a solute

1.Raised Boiling Point: 2.Decreased Freezing Temperature 3.Ability to Create Osmotic Pressure 4.Electrically Conductive 5.Decreased Heat Capacity 6.Slowed Evaporation

Raised Boiling Point Seawater boils at a slightly higher temperature than pure fresh water

Decreased Freezing Temperature Salinity Increases, Water Resists Freezing * How can this be helpful to us?

Create Osmotic Pressure Osmosis: movement of fluid across a semipermeable membrane from high to low concentration Osmotic Pressure: water pressing against the membrane

Electrically Conductive Salts are Electrolytes: conduct electricity when dissolved in water

Heat Capacity Less heat to raise the temperature of seawater

Evaporation Because of attraction between ions, seawater will evaporate more slowly than fresh water

Principle of Constant Proportions Almost every known, naturally occurring element- exists in seawater Proportions stay the same Only water and salinity changes

Determining Salinity *Chloride accounts for 55.04% of dissolved salts -Salinity ppt = x chlorinity ppt Example 1: Seawater sample that tests for 19.2 ppt * What is the salinity of this sample?

Salinity ppt = x 19.2 ppt – Salinity ppt = ppt Example 2: You know a sample of seawater has a chlorinity of 18.3 ppt. What is the salinity?

Salinometer Determines salinity by determining the electrical conductivity of the water

CTD Sensor * Primary tools for measuring the properties of seawater Conductivity Temperature Depth