DO NOW: CURRENT EVENTS

Take out your current events. You will summarize the article for the

class.

Water

Water - A Polar Molecule

-The average salinity of ocean water is 2.5% salt. (That’s 97.5% water)

-The average temperature of all the ocean water on the planet is 39ºF. (At the surface the average is closer to 62ºF.)

-At its deepest known point, ocean water pushes inward with a pressure equal to one human trying to hold 50 jumbo jets at one time. (depth of 36,000 ft)

-Ocean water makes up 99% of the livable space on our planet.

-The top 10 feet of ocean water holds more heat than the entire atmosphere.

-The Gulf Stream (ocean current in Atlantic) moves more water in one day than all the rivers on Earth combined. In areas, it flows at speeds

300 times faster than the Amazon River.

-Antarctica has as much ice as the Atlantic Ocean has salt water.

-A mouthful of sea water typically contains millions of bacteria, hundreds of thousands of phytoplankton, and tens of thousands of zooplankton

-Water molecules are composed of one oxygen and two hydrogen molecules:

Water is considered to be a POLAR molecule because it has partial + and – charges**Each H is slightly positive……..each O is slightly negative

This property alone is responsible for the various unique and amazing properties of water.

**The bond formed between a H and an O in the same water molecule is a COVALENT BOND.

*Due to this polarity water is highly attracted to other materials and other water molecules:

-COHESION: water sticking to other water molecules

-ADHESION: water sticking to other materials

+ +

++

- -

**The bond formed between a H and an O in 2 different water molecules is a HYDROGEN BOND

**A complete salt molecule is NaCl, which is separated into Na+ and Cl- when it is dissolved in water.

UNIVERSAL SOLVENT: Water has a unique ability to dissolve a huge number of other substances.

**Water can dissolve nearly any substance that has polarity (positive and/or negative charge)

This is an example of a simple oil molecule, which cannot be broken

down and surrounded by polar water molecules.

-Solute: substance that is dissolved.-Solvent: substance that does the dissolving (usually water)

SURFACE TENSION: The “skin” formed at the top of any body of water due to water molecules pulling on one another.

**Another property caused by polarity.

The water molecules under the surface pull on each other, causing the tightness across the surface.

ICE IS LESS DENSE THAN LIQUID WATERNormally when we think of a solid substance, it is more dense than the liquid form because the molecules get closer together as they cool.

**At 4°C, water molecules start to spread out (crystallize).**At 0°C, water is completely frozen (least dense it can be)

Liquid H20 at 4°C Frozen H2O at 0°C

Molecules crystallize

Ocean water freezes at -1.9ºC, but it leaves the salt behind! It can be melted to drink

VISCOSITY: The tendency for a fluid to resist flow.**When fluids are cooled, they become more viscous (the resist flow more)**When they are heated, they become less viscous (easier for them to flow)

-A 20°C decrease in temperature will increase waters viscosity by over 60%.

This becomes a big problem for any organism which exerts a lot of energy to move through the water. It becomes very difficult for them to keep moving.

For larger organisms who do not exert as much energy to move, this change in viscosity does not matter.

ACID – A substance with a pH lower than 7.**This is caused by an abundance of H+ ions in a solution**Examples

BASE – A substance with a pH above 7.**Caused by an abundance of OH- or a lack of H+ ions.**Examples

**The term pH stands for the potential of hydrogen

pH scale