` Complete the diagram for the water cycle and explain why it is so important on Earth. 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 Nickname is the “ Mickey Mouse Molecule” H+ H+ O-

Properties of Water 1. At sea level, pure water boils at 100 °C and freezes at 0 °C. The boiling temperature of water decreases at higher elevations (lower atmospheric pressure). For this reason, an egg will take longer to boil at higher altitudes 1

2. 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 1

Helps insects walk across water 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 1

Adhesion Also Causes Water to … Attach to a silken spider web Form spheres & hold onto plant leaves

3. High 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. 1

4. High Heat of Vaporization Amount of energy to convert 1g or a substance from a liquid to a gas. Water needs to gain 540 cal/g for evaporation to occur. In order for water to evaporate, hydrogen bonds must be broken. As water evaporates, it removes a lot of heat with it (a cooling effect). 1

Heat radiated from the sun-warmed surface of the earth is 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. 1

5. Density of Water in solid form is low a. Liquid water has hydrogen bonds that are constantly being broken and reformed. Frozen water forms a crystal-like framework that sets molecules at fixed distances apart-therefore ice floats. This prevents water from freezing from the bottom up. Ice forms on the surface first—the freezing of the water releases heat to the water below creating insulation. This makes transition between seasons less abrupt.

Water is Less Dense as a Solid Which is ice and which is water? 1

Water is Less Dense as a Solid Ice 1

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

1. Solution- a mixture where components are evenly distributed 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

8. Water is usually a neutral substance with a pH of 7. 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. pH Scale-a measurement system the indicates the concentration of how acidic or basic a substance is. Acids-pH less than 7. Stomach acid, lemons Bases-pH of more than 7 like milk, bleach, ammonia

9. Homeostasis-Ability to maintain a steady state despite changing conditions Water is important to this process because: a. Makes a good insulator b. Resists temperature change c. Universal solvent d. Coolant e. Ice protects against temperature extremes (insulates frozen lakes) 4