Water Unit

SOL 6.5

The student will investigate and understand the unique properties and characteristics of water and

its roles in the natural and human-made environment. Key concepts include

a) water as the universal solvent; b) the properties of water in all three states; c) the action of water in physical and chemical

weathering; d) the ability of large bodies of water to store heat

and moderate climate; e) the origin and occurrence of water on Earth; f) the importance of water for agriculture, power

generation, and public health; and

g) the importance of protecting and maintaining water resources.

Web Sites:

http://www.unesco.org/water/

http://www.wateryear2003.org/en/ev.php-URL_ID=1462&URL_DO=DO_TOPIC&URL_SECTION=201.html

Youtube clips

http://www.youtube.com/watch?v=KiZJOTt3Dl0&feature=fvw

http://www.youtube.com/watch?v=KiZJOTt3Dl0&feature=fvw

http://www.youtube.com/watch?v=VGoJuLX3BQQ&NR=1&feature=fvwp

http://www.youtube.com/watch?v=DVCYlST6mYQ&safety_mode=true&persist_safety_mode=1&safe=active 10 minute video on properties of water……NICE

Water can be found in most areas of the Earth.

Water is found naturally as

a Liquid

http://static.guim.co.uk/Guardian/society/gallery/2007/jul/11/childrensservices/GD3984317@Wat

er-Babies---pics-s-550.jpg

http://www.depts.ttu.edu/CASNR/Water/water1.jpg

Solid

Gas

Water: the Universal Solvent

Water is Unique!

Why?

1. Only compound that

commonly exist in

all 3 forms in nature

(solid,liquid,gas)

2. Universal solvent

(many, many

materials dissolve in

H2O

3. Polar molecule (1

side slightly positive,

1 side slightly

negative) (leading to

cohesion, adhesion,

capillary action)

4. High surface tension

This daisy is under the

water level, which has risen gently and smoothly. Surface tension

prevents the water from submerging the flower.

5. Large range of

temps (0-100C)

liquid form WOW! The following link is good.

http://www.nyu.edu/pages/mathmol/textbook/info_wa

ter.html This is a fine link for studying water.

http://www.youtube.com/watch?v=Jy65YrPYZb0

Water, the great mystery. One of a number of

segments.

WATER

FORMULA for WATER

DIAGRAM of a WATER MOLECULE

POLAR MOLECULE

ADHESION

COHESION

MISCIBILITY

SOLVENT

SOLUTE

SOLUBLE/SOLUBILITY/SOLUTION

SURFACE TENSION

MENISCUS

Reservoir Volume 103 km3

%total Residence

Time

Ocean 1,370,0

00

97.25 > 3000

years

Glaciers &

Ice caps

29,000 2.05 10 - 100

thousand

years

groundwater 9500 0.68 Highly

variable, 10 -

300

Lakes 125 0.01 several

years

Soils 0.005 .005 1- 2 years

Atmospher

e

13 0.001 10 days

*but high

flux!

Rivers 1.7 0.0001 2 - 3

weeks

Biosphere 0.60 0.0000

4

weeks -

years

Total 1,408,7

00

100

Water that exists on, at or within the

Earth’s surface layer is termed the

hydrosphere.

Random Fact: Water weighs 8.37

pounds per gallon at 4 degrees C.

H2O The Mickey Mouse Molecule

Water is a polar molecule which gives each molecule the appearance of “Mickey Mouse ears”.

Atomic Structure of Water

2 hydrogen atoms bonded to 1 oxygen atom causes unique electrochemical properties.

Hydrogen side has slight positive charge. Other side has negative charge.

Hydrogen atoms form 105O angle

All atoms aspire to completely fill their orbitals. When the orbitals are full, there are no valence electrons available to participate in chemical bonds. So these atoms get left alone! That is why we call helium, neon, argon, krypton, and xenon INERT. They have full orbitals, so they have no way to interact with other elements.

Hydrogen would like to have 1 more electron to fill up its' orbital. Oxygen would love to have 2 more to fill up its' 2nd orbital. SO HYDROGEN AND OXYGEN SHARE ELECTRONS, which makes both of them happy. This is called a covalent bond.

Covalent bond: the sharing of electrons between atoms.

THE HYDROGEN BOND IS WHAT GIVES WATER IT’S HEAT CAPACITY, IT’S DENSITY BEHAVIOR, AND DISSOLVING ABILITY.

www.geo.umn.edu/

Properties Key to Life Handouts.doc

(honors)

Properties Key to Life Handouts Academic.doc (academic)

Temperature (degrees

Celsius) Density (grams per cubic

centimeter)

0 (solid) 0.9150

0 (liquid) 0.9999

2 1.0000

20 0.9982

40 0.9922

60 0.9832

80 0.9718

100 (gas) 0.0006

Freezing Point = Melting Point

Using the Pressure Cooker at High Altitudes

At High Altitude (3500-6500 ft) cooks really have

to plan ahead to do some of the same things the

rest of us take fro granted. The reason foods have

high altitude instructions is because the boiling point

of water changes with altitude. As you go higher, the

boiling temperature decreases. At sea level, the

boiling point of water is 212° F (100° C). As a

general rule, the boiling point temperature

decreases by 1 degree F for every 540 feet of

altitude (0.56° C for every 165 meters). On top of

the14,000 foot Pike's Peak, for example, the boiling

point of water is 187° F (86° C).

Figuring Altitude in Pressure Cooking

In order to cook at elevations above 2000 feet,

the cooking times in a standard pressure cooker

must be altered according to a very specific formula:

For every 1000 ft above 2000 ft

elevation, increase the cooking time by 5%.

Using a little basic physics we know that water

boils at 212°F at sea level, but as altitude increases

the temperature at which water boils decreases at

the rate of 1.9°F for each 1,000 feet because there

is less atmospheric pressure on the surface of

liquids. By adding 5PSI, water boils at about 16°F

higher than it naturally would at that altitude; at

10PSI it boils at 28 °F higher, and at 15PSI, water

boils 38°F higher. Therefore, by increasing the

pressure, as in a pressure cooker, the temperature

Boiling Point Of Water*

Altitude

in

Feet

Altit

ude in

Meters

Deg

rees F.

Deg

rees C.

0 0 212.

0

100.

0

500 152 211.

0

99.4

1000 305 210.

0

98.9

2000 610 208.

2

97.9

3000 914 206.

2

96.8

4000 121

9

204.

4

95.8

5000 152

4

202.

6

94.8

6000 182

9

200.

7

93.7

7000 213

4

198.

7

92.6

8000 243

8

196.

9

91.6

10,00

0

304

8

194.

0

90.0

12,50

0

381

0

189.

8

87.7

14,00 426 187. 86.3

at which water boils is raised and the food is cooked

more quickly.

A standard pressure cooker operating at 15 PSI,

rises the boiling point of water to 250°F (121°C) at

sea level. At 240°F (which corresponds to only 10.5

PSI) the cooking times must be increased by 33% in

comparison to the standard 15PSI.

0 7 3

* = These temperatures will all vary

according to whatever your current

barometric pressure is. The ONLY way

to find the exact boiling point is to take

standard barometric pressure (29.92

millibars) and subtract the local

barometric pressure (found on a

barometer or in the local weather

forecast). Multiply the resulting number

by 1.8518. Add 212 to that and you will

find the current boiling point of water

wherever you happen to be at the time

of testing (altitude does not matter). If

you use this formula to find the boiling

point, the result will only be correct for

a short while because the barometric

pressure is always changing. You'll

need to get an updated local

barometric pressure and refigure the

formula.

Surface Tension

The following illustration shows how water molecules are attracted to each other to create high surface tension. This property can cause water to exist as an extensive thin film over solid surfaces. In the example above, the film is two layers of water molecules thick.

Solution, Solvent, Solute

The larger amount is the SOLVENT. The lesser amount is the SOLUTE. A SOLUTION is a mixture of one substance (SOLUTE) dissolved (evenly distributed) in another, larger substance (SOLVENT) http://www.chemistryland.com/CHM107/Water/WaterTutorial.htm

The motto

regarding

solubility is "Like Dissolves Like." For example, to clean off

grease, use something that is greasy like vegetable oil or

butter. I had one student say he noticed potato chips

cleaned his hands. It must have been the oil in the chips.

http://www.chemistryland.com/CHM107/Water/WaterTutorial.htm

This child has a

clean face now, but

after eating the cotton

candy, it won't be. To

clean off cotton candy

we know that water

would good for that, not

oil. Remembering "Like Dissolves Like" we guess that water

and sugar must be alike in some way.

Here is a 3-d model of the sugar, glucose. I've placed water molecules at strategic places around the sugar molecule. Do you notice that the positive side of water is attracted to

the negative oxygen atoms? The negative side of water is attracted to the positive hydrogens which are bonded to the oxygens (not the other hydrogens bonded to carbons). Because water pulls the charged areas, it will pull the sugar into the water and hold it there. That's why water is good at cleaning the face of someone eating cotton candy or other sweets.

Water is known as the

Universal Solvent

Water is a good solvent due to

its polarity. Substances that will

mix well and dissolve in water

(e.g. salts) are known as

"hydrophilic" (water-loving)

substances, while those that do

not mix well with water (e.g. fats

and oils), are known as

"hydrophobic" (water-fearing)

substances.

LIKE MOLECULES DISSOLVE LIKE

Polar dissolve polar

COHESION

A property of water

and some other

substances in which

the molecules are

attracted to molecules

of the same substance.

Water molecules, being

polar, act like LITTLE

MAGNETS—they are

attracted to poles of

opposite charges.

ADHESION

When water molecules are attracted to molecules of a different substance.

http://www.nano-

world.org/frictionmodule/content/0200makroreibung/0600adhesionmodel/bild1.gif

CAPILLARY ACTION

Water molecules love some other molecules and

hate other molecules.

When water molecules stick to

other molecules that are also little

magnets, it is called "molecular

adhesion." This explains why it is

easy to clean up spilled water with

a paper towel: the water

molecule's little magnets like to stick to the cellulose molecules of

the paper, which are also like little magnets. Water molecules will

stick to any other molecules that

are like little magnets (polar), but do not like to get involved with

any molecules that hate little

magnets (nonpolar), like oil. Oil and water don't mix, right? That is

why you have to shake the salad dressing real hard before you pour

it: the oil molecules hate the water little magnets.

Paper towels are made out of

trees,

http://www.sciencebuddies.org/science-fair-projects/project_ideas/PlantBio_img014.jpg

and trees are made out of cellulose. The leaves make

molecules of sugar out of sunlight, water, and carbon dioxide, then

combine the sugars into huge

sugar chains. These sugar chain molecules are called cellulose. This

name comes from the fact that the plant material is made of cells, and

the "-ose" word ending means

"sugar". Cellulose is also a

great magnet (polar molecule), so water sticks to

cellulose just like a magnet to the refrigerator door!

Now that we know a bit

about water molecules, let's

look at how water acts in a little tube.

The redwood tree's trunk is made up of millions of

little bitty tubes (xylem), and these tubes are made of cellulose. The

water molecules like to stick together and like to stick to the walls of the

tubes of cellulose, so they rise up the tubes by capillary action.

The water pressure decreases as it rises up the tree. This is because the capillary action is

fighting the weight of the water. Although the xylem tube is very thin, and therefore the weight of

the water is very low, it is not zero. Eventually, the effects of gravity on the water starts to

equal the effects of capillary action. http://www.davidlnelson.md/Cazadero/Trees&CapillaryAction.htm

Drawing pig blood into a pipette=capillary action

http://oslovet.veths.no/teaching/pig/pigbleed/2.jpg

http://www.mobot.org/gardeninghelp/images/factsheets/2b.jpg

REVIEW http://www.ccs.k12.in.us/

chsBS/kons/kons/physical_properties_of_water.html

http://ga.water.usgs.gov/edu/waterproperties.html

http://kentsimmons.uwinnipeg.ca/cm1504/water.htm

Because water absorbs strongly in the infrared portion of the light spectrum, a small amount of visible red light is absorbed as well, resulting in water's slightly blue color when seen in mass quantities such as a lake or ocean.

UNIQUE PROPERTIES OF WATER?

1.

2.

3.

4.

5.

6.