H H Water • A water molecule (H2O), is made up of threeatoms --- one oxygen and two hydrogen. O
Water is Polar • In each water molecule, the oxygen atom attracts more than its "fair share" of electrons • The oxygen end “acts” negative • The hydrogen end “acts” positive • Causes the water to be POLAR • However, Water is neutral (equal number of e- and p+) --- Zero Net Charge
Hydrogen Bonds Exist Between Water Molecules • Formed between a highly Electronegative atom of a polar molecule and a Hydrogen • One hydrogen bond is weak , but many hydrogen bonds are strong
Interaction Between Water Molecules Negative Oxygen end of one water molecule is attracted to the Positive Hydrogen end of another water molecule to form a HYDROGEN BOND
Properties of Water • 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
Properties of Water • Cohesion
Cohesion • Attraction between particles of the same substance (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 … Helps insects walk across water
Properties of Water • Cohesion • Adhesion
Adhesion • Attraction between two different substances. • Water will make hydrogen bonds with other surfaces such as glass, soil, plant tissues, and cotton. • Capillaryaction-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.
Adhesion Causes Capillary Action Which gives water the ability to “climb” structures
Adhesion Also Causes Water to … Attach to a silken spider web Form spheres & hold onto plant leaves
Why does water form? • In a water molecule two hydrogen atoms form single covalent bonds with an oxygen atom. • The bonds are formed to create a “stable” molecule. • Oxygen needs 2 more electrons to be stable. • Hydrogen needs 1 more electron to be stable. *Gives water more structure than other liquids*
Water Activity Sticky Molecule Article • Directions: • Color • All oxygen RED • All hydrogen Blue • Two Electrons Yellow • Cut all circles • Glue • Oxygen nucleus over center of O • Hydrogen nuclei over H • Glue oxygen and Hydrogen to paper • Place electrons ask teacher confirmation. • Glue Electrons • Write Article by answering questions
Water Activity Sticky Molecule Article • Name the elements found in the water molecule. What is the ratio of hydrogen to oxygen. • How does one molecule of water form? What is the name of the bond (label it in your picture) • Describe a polar molecule. Also label this in your picture! • How do two molecules of water stick together? What is the name of the bond and property? • Describe what is happening when water flows down a piece of wet yarn.
Properties of Water • Cohesion • Adhesion • Universal Solvent
Water ……a.k.a the Universal Solvent Water is the solvent of Life! - Because of the polarity water is able to dissolve the many substances. Solute– substance dissolved in a solvent to form a solution Solvent– fluid that dissolves solutes
Properties of Water • Cohesion • Adhesion • High Specific Heat
High Specific Heat • Amount of heat needed to raise or lower 1g of a substance 1° C. • Water resiststemperature change, both for heating and cooling. • Water can absorb or release large amounts of heat energy with little change in actual temperature.
Water holds onto Heat and won’t let it go! • The amount of heat that a substance can “hold” is called Heat Capacity. • Three-fourths of the earth is covered by water. The water serves as a large heat “sink” (or bank) responsible for: • Prevention of temperature fluctuations that are outside the range suitable for life. • Coastal (Beach) areas having a mild climate • A more stable marine (water) environment
Properties of Water • Cohesion • Adhesion • High Specific Heat • High Heat of Vaporization
Properties of Water • Cohesion • Adhesion • High Specific Heat • High Heat of Vaporization • Less Dense as a Solid
Water is Less Dense as a Solid • Ice is less denseas a solid than as a liquid (ice floats) • Liquid water has hydrogen bonds that are constantly being broken and reformed. • Frozen waterforms a crystal-like lattice whereby molecules are set at fixed distances.
Water is Less Dense as a Solid • Which is ice and which is water?
Water is Less Dense as a Solid Water Ice
Only water is found _____________ as a SOLID, LIQUID, and GAS on Earth! While all elements will change states, only some compounds will. Water changes state within a very narrow range, allowing it to snow, rain, and evaporate… all on the same day!
Ice is less dense than liquid water! Solids are usually more dense than liquids because their molecules are closer together. Liquids are more dense than gases… but not for water. Water forms a ___________________ structure which makes ice (solid water) less dense than liquid water.
Solid Organized Liquid Disorganized Gas Free Floating
Water “grows” when freezing: 1. This causes potholes on road and weathering of rocks. 2. It 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 transitions between seasons less abrupt.