Water, Water, and More Water

Why are we covering water again you ask? Well…..

Freshwater: a hot commodity

• Affects politics, and economies more than you would guess! – Food– Shipping transport– Fresh water sources – Oil and gas

• A source of political tension – Redirecting rivers – Pollution

• Ethiopia vs. Egypt • Georgia vs. Florida

Water wars

• Varning: graphic image at the 2 minute mark • If you are squeamish close your eyes when you

see the earth go brown.

Movid: http://wwwyoutube.com/watch?v=Ikb4WG8UJRw&safety_modd=true&persist_safety_mode=1&sáfe=active

Marine Science: IT’S A REALLY BIG DEAL!

• Covers 71% or earth’s surface but 99% of the biosphere

• FLASHCARD ALERT: biosphere: the habitable space on earth

• We need fresh water! • A lot is frozen

Ancient Water

• Scientists think the same water you drink today is billions of years old

• Travels through hydrologic cycle – Changes form:

evaporates, condenses,

The Water Cycle

The Water Cycle

• Sun = heat = water vapor • FLASH CARD ALERT: TRANSPIRATION:

Water vapor also given off from plants• As it rises it gives off heat and condenses =

condensation – Falls back to earth as rain or snow

• Flows into rivers • Organisms consume and release it again

• “One molecule, over time, may have flowed through dozens of rivers and been part of every ocean. It may have been in the tears of an Egyptian pharaoh, and, centuries later, joined a glistening dewdrop on corn in Thomas Jefferson’s fields.“

The Polar Molecule

• Hydrogen atoms bond to oxygen atom with a covalent bond: – FLASH CARD ALERT:

covalent bond: formed by atoms sharing electrons

• Water is a very stable molecule

• Polarity allows it to bond with adjacent water molecules (think of magnets)

Allows for the invention of microwaves!

• Heat the food but not the container – Container gets hot

by conducting heat from the food

• WHY!?!– Microwaves produce

heat by taking advantage of water’s polar nature.

Hydrogen bonds allow water to….

• be liquid at room temperature

• Cohesion and Adhesion

• Viscosity….

• Surface Tension…

Viscosity

• cooler water has less molecular motion to counteract the hydrogen bonds so water molecules stick together more than in warmer water– Affects the energy

aquatic organisms expend

– Cool water: plankton use less energy to keep from sinking

– Swimming animals use more

Surface Tension

• Caused by cohesion • Neuston: plankton that live

on water’s surface – Do not float. Rest on the

surface tension – Soap/chemicals break

surface tension = drowning hazard.

• Air/water boundary– Affects how quickly the

ocean takes up atmospheric carbon dioxide and releases oxygen

Floating Solids • Ice Floats

– Less dense than liquid water

• HUGE EFECT ON THE TEMPERATURE OF THE EARTH!! – Insulates water below:

allows it to stay liquid and retain heat

– If ice sank, ocean would be entirely frozen in some parts and much cooler in others = much colder climate for all of earth

Special Solutions: Salt water

• Solution = mixture– Combination of two or more substances

that are NOT chemically bonded and not in fixed proportions to each other.

• Homogeneous and heterogeneous

• Water: universal solvent

How you get salt water

• Water pulls apart salt crystal: NaCl– The separate sodium and chloride become

charged molecules and attract the positive and negative ends of water.

• Bond to the water molecules

• This bonding changes some of water’s physical properties by disrupting the hydrogen bonds

• Colligative properties: properties of a liquid that may be altered by the presence of a solute– Why doesn’t fresh water have colligative

properties?

Colligative Properties of Seawater

• Raised boiling point: boils at hier temperature • Decrease freezing point: as salinity increases water

resists freezing – Why salt is used on the road during ice and snowstorms

• Ability to create osmotic pressure: aka unequal pressure of water molecules to cause diffusion

• Electrically conductive: Salts in seawater conduct electricity

• Decreased heat capacity: takes less to raise temp of sea water

• Slowed evaporation: attraction between ions and water molecules keeps water from evaporating easily

Salinity:

• FLASHCARD ALERT: SALINITY: the total quantity or concentration of all dissolved inorganic solids, or ions.

• Salinity varies – Weather, rainfall, evaporation

• Different in primarily bays, semi-enclosed seas, mouths of large rivers

• FLASH CARD ALERT: HALOCLINE: transition from low-salinity surface waters to high-salinity deep waters

Ocean Temperature

• Density differences cause water to separate into layers – High density below low density – Water’s density is a result of its

temperature and salinity characteristics

• Temperature affects density of water – Usually wins out except in places where

fresh water mixes with seawater