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1. Complete the diagram for the water cycle and explain why it is so important on Earth.

2. What is the source of energy for the water cycle?

C. Water-An Extraordinary Substance

• Water is the single most abundant substance on Earth

• It is the only substance that exists in all three physical states of matter

• Water is a Polar molecule because it has opposite charges between oxygen and hydrogen atoms on opposite ends

a. Formula-2 hydrogen atoms; 1 oxygen atom

b.Nickname is the “ Mickey Mouse Molecule”

H+ H+

O-

•Properties of WaterProperties of Water

1. At sea level, pure water 1. At sea level, pure water boilsboils at at 100 °C 100 °C and and freezesfreezes at at 0 °C0 °C. .

• The boiling temperature of water The boiling temperature of water decreases at higher elevations decreases at higher elevations (lower atmospheric pressure). (lower atmospheric pressure).

• For this reason, an egg will take For this reason, an egg will take longer to boil at higher altitudeslonger to boil at higher altitudes

2. Water is a2. Water is a very “sticky” substance because of the way hydrogen and oxygen bond

a. Cohesion-Attraction between particles of the same substance (this is why water is attracted to itself)– Results in Surface tension (a measure of

the strength of water’s surface)

– Produces a surface film on water that allows insects to walk on the surface of water

Cohesion …Cohesion …

Helps insects walk across water

b. Adhesion--Attraction between two different substances.– Water will make hydrogen bonds with

other surfaces such as glass, soil, plant tissues, and cotton.

– Causes capillary action-water molecules will “tow” each other along when in a thin glass tube.•Example: transpiration process which

plants and trees remove water from the soil, and paper towels soak up water.

•Capillary action gives water the ability to “climb” structures

Adhesion Also Causes Adhesion Also Causes Water to …Water to …

Form spheres & hold onto plant

leaves

Attach to a silken spider web

3. 3. High Specific HeatHigh Specific Heat--Amount of heat needed to

raise or lower 1g of a substance 1° C.

• This is why it takes water longer to heat up and cool down

• It helps prevent big temperature fluctuations that are outside the range suitable for life. This is why fish can still live in frozen lakes and ponds.

4. High Heat of 4. High Heat of VaporizationVaporization• Amount of energy to convert 1g or Amount of energy to convert 1g or

a substance from a a substance from a liquid to a gas. liquid to a gas. Water needs to Water needs to gaingain 540 cal/g for 540 cal/g for evaporation to occur.evaporation to occur.

• In order for water to evaporateIn order for water to evaporate, , hydrogen bonds must be brokenhydrogen bonds must be broken..

• As water evaporatesAs water evaporates, , it removes a it removes a lot oflot of heatheat with it (a cooling effect)with it (a cooling effect)..

•Water vapor Water vapor forms a kind of global ‘‘blanket” which helps to keep the Earth warm.

•Heat radiated from the sun-warmed surface of the earth is

absorbed and held by the vapor.

5. Density of Water in solid form is lowa. Liquid water has hydrogen bonds hydrogen bonds that are

constantly being broken and reformed. Frozen constantly being broken and reformed. Frozen

water water forms a crystal-like frameworkcrystal-like framework that sets molecules at fixed distances apart-therefore ice floats.b.This prevents water from freezing from the bottom up.c.Ice forms on the surface first—the freezing of the water releases heat to the water below creating insulation.d.This makes transition between seasons less abrupt.

Water is Less Dense as Water is Less Dense as a Solida Solid

•Which is ice and which is Which is ice and which is

water?water?

Water is Less Dense as a Water is Less Dense as a SolidSolid

WaterWater IceIce

6. Water is the “universal solvent” because it dissolves almost everything; The greatest on Earth!a. Solute-substance that is dissolvedb. Solvent-substance that dissolves

the solute

**water is “hard” when lots of minerals are dissolved in it and “soft” when a small amount of dissolved minerals are present

c. Water forms many mixtures-two or more substances joined physically but not chemically (Water often involved). 2 basic types.

1. Solution- a mixture where components are evenly distributed

2. Suspension-a mixture in which materials do not dissolve but break into smaller pieces

7. Water has the ability to be a part of over 550 million reactions. Without it, life would come to a grinding halt on Earth.

8. Water is usually a neutral substance with a pH of 7.a. pH Scale-a measurement system the

indicates the concentration of how acidic or basic a substance is.

1. Acids-pH less than 7. Stomach acid, lemons2. Bases-pH of more than 7 like milk, bleach,

ammonia

9. Homeostasis-9. Homeostasis-Ability to maintain a steady state despite changing conditions

• Water is important to this process because:a. Makes a good insulatorb. Resists temperature changec. Universal solventd. Coolante. Ice protects against

temperature extremes (insulates frozen lakes)