waterproperties

waterproperties - The Extraordinary Properties of Water of...

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Unformatted text preview: The Extraordinary Properties of Water of Water Water • A water molecule (H2O), is made up of three atoms --- one oxygen three and two hydrogen. H O H Water is Polar Water • In each water molecule, the oxygen atom attracts more than its "fair share" atom of electrons electrons • The oxygen end “acts” negative oxygen negative • The hydrogen end “acts” positive hydrogen positive • Causes the water to be POLAR POLAR • However, Water is neutral (equal neutral number of e- and p+) --- Zero Net Charge Charge Hydrogen Bonds Exist Between Water Molecules Between • Formed between a highly Formed Electronegative atom of a polar molecule and a Hydrogen Hydrogen • One hydrogen bond is weak , but many weak many hydrogen bonds are strong strong Interaction Between Water Molecules Molecules Negative Oxygen end of one water molecule is attracted Negative to the Positive Hydrogen end of another water molecule to form a HYDROGEN BOND HYDROGEN What are the Properties of Water? of Properties of Water Properties • At sea level, pure water boils at 100 At °C and freezes at 0 °C. °C freezes • The boiling temperature of water The decreases at higher elevations (lower atmospheric pressure). • For this reason, an egg will take For egg longer to boil at higher altitudes at Properties of Water Properties •Cohesion Properties of Water Properties •Cohesion •Adhesion Properties of Water Properties •Cohesion •Adhesion •High Specific Heat Properties of Water Properties •Cohesion •Adhesion •High Specific Heat •High Heat of Vaporization Properties of Water Properties •Cohesion •Adhesion •High Specific Heat •High Heat of Vaporization •Less Dense as a Solid Cohesion Cohesion • Attraction between particles of the Attraction same substance ( why water is attracted to itself) attracted • Results in Surface tension (a measure Results Surface of the strength of water’s surface) of • Produces a surface film on water that Produces allows insects to walk on the surface of allows water Cohesion … Cohesion Helps insects walk across water Adhesion Adhesion • Attraction between two different substances. • Water will make hydrogen bonds with other Water surfaces such as glass, soil, plant tissues, surfaces and cotton. • Capillary action-water molecules will “tow” action-water each other along when in a thin glass tube. each • Example: transpiration process which plants Example: transpiration and trees remove water from the soil, and paper towels soak up water. paper Adhesion Causes Capillary Action Action Which gives water the ability to “climb” structures Adhesion Also Causes Water to … Water Form spheres & hold onto plant leaves Attach to a silken spider web High Specific Heat High • Amount of heat needed to raise or lower 1g of a substance 1° C. 1g 1° • Water resists temperature change, Water resists temperature both for heating and cooling. both • Water can absorb or release large Water amounts of heat energy with little change in actual temperature. change High Heat of Vaporization High • Amount of energy to convert 1g or a Amount substance from a liquid to a gas liquid • In order for water to evaporate, In hydrogen bonds must be broken. hydrogen • As water evaporates, it removes a lot it of heat with it. heat High Heat of Vaporization High • Water's heat of vaporization is 540 cal/g. cal/g. • In order for water to evaporate, each In evaporate each gram must GAIN 540 calories (temperature doesn’t change --100oC). 100 • As water evaporates, it removes a lot it of heat with it (cooling effect). heat (cooling • Water vapor forms a kind of Water global ‘‘blanket” which helps to keep the Earth warm. • Heat radiated from the sun Heat warmed surface of the earth is absorbed and held by the vapor. by Water is Less Dense as a Solid Solid • Ice is less dense as a solid than as a liquid (ice floats) • Liquid water has hydrogen bonds that are constantly being broken and reformed. reformed. • Frozen water forms a crystal-like lattice whereby molecules are set at lattice fixed distances. Water is Less Dense as a Solid Solid •Which is ice and which is water? Water is Less Dense as a Solid Solid Water Ice Homeostasis Homeostasis • Ability to maintain a steady state Ability despite changing conditions despite • Water is important to this process Water because: because: a. Makes a good insulator a. good b. Resists temperature change c. Universal solvent c. Universal d. Coolant e. Ice protects against temperature e. extremes (insulates frozen lakes) Solutions & Suspensions Solutions • Water is usually part of a Water mixture. mixture. • There are two types of mixtures: – Solutions – Suspensions Solution Solution • Ionic compounds disperse as ions in Ionic ions water water • Evenly distributed • SOLUTE – Substance that is being dissolved • SOLVENT – Substance into which the solute Substance dissolves dissolves Solution Solution Suspensions Suspensions • Substances that don’t dissolve but separate into tiny pieces. • Water keeps the Water pieces suspended so they don’t settle out. Acids, Bases and pH Acids, One water molecule in 550 million One naturally dissociates into a Hydrogen dissociates Ion (H+) and a Hydroxide Ion (OH-) (OH-) H2O H + OH + Hydrogen Ion Hydrogen Acid - Hydroxide Ion Base Base The pH Scale The • Indicates the concentration of H+ concentration ions ions • Ranges from 0 – 14 14 • pH of 7 is neutral is • pH 0 up to 7 is acid … H+ • pH above 7 – 14 is basic… OHabove • Each pH unit represents a factor of 10X change in concentration • pH 3 is 10 x 10 x 10 (1000) stronger pH than a pH of 6 than Acids Acids • Strong Acids have a pH of 1-3 1-3 • Produce Produce lots of H+ ions ions Bases Bases • Strong Strong Bases have a pH of 11 to 14 • Contain lots of OHlots ions and ions fewer H+ ions Buffers Buffers • Weak acids or bases that react with Weak strong acids or bases to prevent sharp, sudden changes in pH (neutralization). (neutralization). • Produced naturally by the body to Produced maintain homeostasis maintain Weak Acid Weak Base ...
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This note was uploaded on 11/09/2011 for the course BIO 110 taught by Professor Harmon during the Winter '11 term at BYU.

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