The Extraordinary Properties of Water

INK PAIR SHARE One of NASA’s missions is to search the universe for water. Why water specifically?

Water threeA water molecule (H 2 O), is made up of three atoms --- one oxygen and two hydrogen. H H O

Water is Polar Polar Molecules = molecules with unequal distribution of charge; one positive end & one negative end oxygen hogs all the electrons.In each water molecule, the oxygen hogs all the electrons. oxygen negativeThe oxygen end “acts” negative hydrogen positiveThe hydrogen end “acts” positive On your drawing, color the Oxygen RED and the Hydrogen BLUE

Hydrogen Bonds Exist Between Water Molecules Weak hydrogen bonds connect water moleculesWeak hydrogen bonds connect water molecules This gives water a high specific heat (this means that H 2 O resists changes in temperature which helps cells to maintain homeostasis)This gives water a high specific heat (this means that H 2 O resists changes in temperature which helps cells to maintain homeostasis) Just like magnets, the opposite poles of the molecules allow them to stick together!

INK PAIR SHARE Why does it feel colder if you sick your hand in ice water compared to sticking your hand in the freezer?

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

What are the Properties of Water?

Universal Solvent Water is the solvent of Life and can dissolve almost anything! Solute – substance dissolved in a solvent to form a solution Solvent – fluid that dissolves solutes (present in the greatest amounts) Example: Ice Tea – water is the solvent and tea and sugar the solutes

Universal Solvent Polar substances dissolve in water –Hydrophilic (water- loving) –Salt/sugar Non-polar substances do not dissolve in water –Hydrophobic (water- fearing) –oil

Solution

Cohesion Attraction between particles of the substance (why water is attracted to itself)Attraction between particles of the same substance (why water is attracted to itself) Surface tension a measure of the strength of water’s surface (due to H-bonding) Produces a surface film on water that allows insects to walk on the surface of waterProduces a surface film on water that allows insects to walk on the surface of water Jesus Lizard

Cohesion … Helps insects “walk” across water

INK PAIR SHARE Why did the paper float on the water and not on the water and detergent mix?

Adhesion Attraction between two different substances. Attraction between two different substances. Water will make hydrogen bonds with other surfaces such as glass, soil, plant tissues, and cotton. Water will make hydrogen bonds with other surfaces such as glass, soil, plant tissues, and cotton. Capillary action-water molecules will “tow” each other along when in a thin glass tube.Capillary action-water molecules will “tow” each other along when in a thin glass tube.

Adhesion Causes Capillary Action Which gives water the ability to “climb” structures

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

Insulation Ice is less dense Ice is less dense as a solid than as a liquid (ice floats) hydrogen bonds constantly being broken and reformed. Liquid water has hydrogen bonds that are constantly being broken and reformed. Frozen water crystal lattice Frozen water forms a crystal lattice whereby molecules are set at fixed distances.

INK PAIR SHARE Why is it important to life that ice creates a crystal lattice and floats? HINT: Think of the life in oceans or lakes

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

Acids, Bases and pH One water molecule in 550 million naturally dissociates into a Hydrogen Ion (H+) and a Hydroxide Ion (OH-) Hydrogen Ion Hydroxide Ion Acid Base Acid Base H 2 O  H + + OH -

The pH Scale concentration of H + ionsIndicates the concentration of H + ions 0 – 14Ranges from 0 – 14 7 is neutralpH of 7 is neutral 0 up to 7 is acidpH 0 up to 7 is acid … H + above 7 – 14 is basicpH above 7 – 14 is basic … OH - 10XEach pH unit represents a factor of 10X change in concentration pH 3 is 10 x 10 x 10 (1,000) stronger than a pH of 6pH 3 is 10 x 10 x 10 (1,000) stronger than a pH of 6

The pH Scale low OH- concentration high OH- concentration

Acids Strong Acids have a pH of 0-3Strong Acids have a pH of 0-3 Produce lots of H + ionsProduce lots of H + ions

Bases Strong Bases 11 to 14Strong Bases have a pH of 11 to 14 lots of OH - ionsContain lots of OH - ions and fewer H+ ions

Buffers Weak acids or bases that react with strong acids or bases to prevent sharp, sudden changes in pH (neutralization).Weak acids or bases that react with strong acids or bases to prevent sharp, sudden changes in pH (neutralization). Produced naturally by the body to maintain homeostasisProduced naturally by the body to maintain homeostasis Weak Acid Weak Base