2. AP Biology 2007-2008 Water The Molecule That Supports All Of Life

3. AP Biology The Chemistry Of Water  Water is a polar molecule  The atoms of water are held together by polar covalent bonds  Who wins?  Oxygen(-)?  Hydrogen(+)?

4. AP Biology Noodle time! Do hydrogen bonds hold oxygen and hydrogen together IN water? Pink – Yes Purple – No Yellow – I’m not sure

5. AP Biology Noodle time! What kind of bonds hold the hydrogen atoms to the oxygen atom in H 2 O? Pink – Non-polar covalent Purple – Hydrogen Yellow – Ionic Green – Covalent

6. AP Biology The Chemistry Of Water  Molecules of water are held together by Hydrogen bonds  H + of one water molecule attracted to O - of another water molecule

7. AP Biology The Properties Of Water (Super Powers) 1. Cohesion & Adhesion 2. Good Solvent 3. Low Density As A Solid 4. High Specific Heat 5. Heat Of Vaporization 6. Ionization of Water I’m pretty super!

8. AP Biology 1.Cohesion Try that with flour… or sugar…  Caused by the hydrogen bonds between H 2 O molecules  Makes water “sticky”  Allows for this kid to drink out of his straw  And this guy to walk on water

9. AP Biology 1. Adhesion  Caused by hydrogen bonding between H 2 0 and OTHER molecules  Causes meniscus

10. AP Biology Penny Challenge

11. AP Biology Transpiration Water defies gravity and travels through plants from the roots up. Caused by COHESION & ADHESION!

12. AP Biology 2. Universal Solvent  Solvents dissolve solutes creating solutions  The polarity of H 2 O makes it a good solvent  polar H 2 O molecules surround + & – ions pulling them apart

13. AP Biology Noodle Time  Is any kind of liquid a good solvent?  Let’s try it! A B

14. AP Biology What do you notice?

15. AP Biology Both A and B are POLAR. Is C polar? A B C

16. AP Biology What do you notice?  A = polar  B = polar  C = ?

17. AP Biology What dissolves in water?  Hydrophilic  substances have attraction to H 2 O  polar or non-polar?

18. AP Biology What doesn’t dissolve in water?  Hydrophobic  substances that don’t have an attraction to H 2 O  polar or non-polar? fat (triglycerol)

19. AP Biology 3. Low Density as a solid (Ice Ice Baby)  Most substances are more dense when they are solid, but not water…  Ice floats!  H bonds form a crystal And this has made all the difference!

20. AP Biology Water vs Ice – Use the Water Kits

21. AP Biology Why is “ice floats” important?  Oceans & lakes don’t freeze solid  surface ice insulates water below  allowing life to survive the winter  if ice sank…  ponds, lakes & even oceans would freeze solid  in summer, only upper few inches would thaw  seasonal turnover of lakes  sinking cold H 2 O cycles nutrients in autumn

22. AP Biology The Fireproof Balloon  NOODLE TIME! What will explode first? Pink - A balloon with H 2 O Green - A balloon without H 2 O Why did this happen?

23. AP Biology 4. High Specific Heat  H 2 O resists changes in temperature  high specific heat  takes a lot to heat it up  takes a lot to cool it down  H 2 O moderates temperatures on Earth

24. AP Biology 5. Heat of vaporization Evaporative cooling Organisms rely on heat of vaporization to remove body heat

25. AP Biology Alcohol vs. Water  IN YO’ BODIES!

26. AP Biology 6. Ionization of water & pH  Water ionizes  H + splits off from H 2 O, leaving OH –  if [H + ] = [ - OH], solution is neutral  if [H + ] > [ - OH], solution is acidic  if [H + ] < [ - OH], solution is basic  pH scale  how acidic or basic a solution is  1  7  14 H 2 O  H + + OH –

27. AP Biology pH Scale 10 –1 H + Ion Concentration Examples of Solutions Stomach acid, Lemon juice 1 pH 10 0 Hydrochloric acid0 10 –2 2 10 –3 Vinegar, cola, beer 3 10 –4 Tomatoes 4 10 –5 Black coffee, Rainwater 5 10 –6 Urine, Saliva 6 10 –7 Pure water, Blood 7 10 –8 Seawater 8 10 –9 Baking soda 9 10 –10 Great Salt Lake 10 10 –11 Household ammonia 11 10 –12 Household bleach 12 10 –13 Oven cleaner 13 10 –14 Sodium hydroxide14 tenfold change in H+ ions pH1  pH2 10 -1  10 -2 10 times less H + pH8  pH7 10 -8  10 -7 10 times more H + pH10  pH8 10 -10  10 -8 100 times more H +

28. AP Biology I’m pretty super! Any questions?