1. Business Buy your lab manual ASAP ($3.00 cash), –Friday, 1 - 2, BI261, Quiz next Thursday covering reading materials through that day, i.e. Proteins, Lectures…updated by morning of the lecture.

2. Water is common to all life on Earth.

3. H 2 O Polarity polar molecule, each water molecule can form hydrogen bonds to as many as four other molecules.

4. H 2 O Bonding Forms a rough tetrahedron, hydrogens at two corners, unpaired electrons at two corners.

5. Polar Molecules …when electrons are shared unevenly in a covalent bond, the bond is polar, – substances with polar bonds are hydrophilic.

6. Effects of Water’s Polarity The polarity of water molecules results in hydrogen bonds, Organisms depend on the hydrogen bonding of of water molecules, –cohesion, –adhesion, Water moderates temperatures on Earth, Water is the solvent of life.

7. Cohesion water molecules stick together because of hydrogen bonding, –hydrogen bonds in liquid water last only a few trillionths of a second, –collectively, the hydrogen bonds hold the water together.

8. Cohesion Evaporation from leaves ‘pulls’ water up from the roots. An unbroken ‘transpiration’ stream is required for water transport.

9. Adhesion …water also sticks to other substances. Adhesion of the water to the vessel walls also helps to resist the downward flow of gravity.

10. Surface Tension …a measure of how difficult it is to stretch or break the surface of a liquid, –water has a high surface tension due to the hydrogen bonding of surface molecules.

11. Water - Air Interface water molecules in solution have attractions in all directions, at the surface, nothing counterbalances the downward pull.

13. Water Moderates Temperatures …water is effective as a heat bank because it can absorb or release a relatively large amount of heat with only a small change in its own temperature.

14. Specific Heat …the amount of heat that must be absorbed or lost for 1 g of a substance to change its temperature 1 o C,...calorie: the amount of heat it takes to raise 1 g of H 2 O by 1 o C.

15. Specific Heat Examples Alcohol0.58 Gold0.03 Granite0.19 Iron0.10 olive oil0.47 water1.00 * cal/g o C SubstanceSpecific Heat*

16. Hydrogen Bonds Again …water’s high specific heat is due to the breakdown and formation of hydrogen bonds, …heat energy is absorbed or dissipated by the numerous hydrogen bonds. Remember: heat is a measure of total quantity of kinetic energy due to molecular motion in a body of matter breaking forming

17. Moderates Temperatures … absorbs heat from the sun during the day, –prevents drastic high temperatures, …slowly releases heat at night, –prevents drastic cold temperatures, …moderates large bodies of water and nearby land masses, …also moderates temperatures within organisms.

18. Heat of Vaporization …is the amount of heat a liquid must absorb for 1 g of it to be converted from the liquid to the gaseous state, –580 calories of heat are required to convert 1 g of water to steam.

19. Heat of Vaporization Examples Methanol1100 Ethanol 854 Acetone 523 Benzene 394 Butane 381 water 2,260 * cal/g o C SubstanceHV*

20. Climate …water’s high heat of vaporization helps moderate Earth’s climate, – the extreme heat absorbed by tropical seas is consumed during the evaporation of surface water, –as moist tropical air circulates pole-ward, heat is released as it condenses to form rain.

21. Evaporative Cooling …occurs because the ‘hottest’ molecules are most likely to leave as gas, bodies of water, animals, plants. Sweat

22. Ice Floats …water is less dense as a solid than it is as a liquid,

23. Oceans and Lakes Don’t Freeze Solid …if ice sank, as does most solids, bodies of water would freeze, …floating ice insulates the water, maintaining temperatures near 0 o C.

24. Water is the Solvent of Life …a liquid that is a complete mixture of two or more substances is called a solution, – the dissolving agent is the solvent, –the dissolved substance is the solute, …aqueous solution: is one in which water is the solvent.

25. Water is Not a Universal Solvent …or else nothing would hold it, –biological systems use hydrophobic molecules to ‘contain’ water.

26. Mole …the standard reference unit for the amount of each pure chemical substance is the molecular weight of the substance taken in grams, –H 2 O: H is 1.008 Dalton, O is 16 Dalton, molecular weight of H 2 O is 18.016,...one mole of H 2 O is equal to 18.016 grams.

27. Avagadro’s Number …the number of atoms or molecules in that quantity of a substance that, expressed in grams, is numerically equivalent to the atomic weight: 6.02 X 10 23, …or one mole = 6.02 X 10 23 atoms or molecules.

28. Molarity …the number of moles of solute per liter of solution, –Sugar, C 12 H 22 O 16 (MW = 342), –1 mole of sugar = 342 grams, –342 grams in a liter of water = 1 M, a 1 molar solution.

29. Self Ionization of Water

30. H + is a Proton …in pure water, only one in 554 million molecules is auto-ionized, –[H + ] (hydrogen ions) in pure water is 10 -7 M (at 25 o C), –[OH - ] (hydroxide ions) is the same.

31. Acids …acids: increase [H + ] in aqueous solutions, –when HCl (hydrocloric acid) is added to water, HCl ----> H + + Cl - hydrogen ion

32. Bases …bases: reduces [H + ] in aqueous solutions, –when NaOH (hydrocloric acid) is added to water, NaOH ----> Na + + OH - OH - + H + ----> H 2 O hydroxide ion combines with H + to form water. removes H +.

33. Bases …bases: reduces [H + ] in aqueous solutions, –when NH 3 (ammonia) is added to water, NH 3 + H + NH 4 + Ammonium ion takes H +.

34. Strong/Weak Acids …strong acids: dissociate completely when mixed in water, HCl ----> H + + Cl - …weak acids: the binding and dissociation of the H + ion is readily reversible, H 2 CO 3 HCO 3 - + H +

35. Strong/Weak Bases …strong bases: dissociate completely when mixed in water, NaOH ----> Na + + OH - …weak bases: the binding and dissociation of the OH - ion is readily reversible, NH 3 + H + NH 4 +

36. pH is the measure of [H + ] …acid and base refer to compounds and ions, …acidic and basic refer to solutions.

37. H + and OH - ions …in any aqueous solution the concentration of the H + and OH - ions is constant at 10 -14 M, [H + ] [OH - ] = 10 -14 M …if [H + ] is 10 -7, then [OH - ] is 10 -7,...if [H + ] is 10 -5, then [OH - ] is 10 -9.

38. pH …to conveniently express the variation in the concentrations of H + and OH - ions, scientists use the pH scale, –pH (potential of Hydrogen): is the negative logarithm of [H + ], pH = -log 10 [H + ]

39. pH = -log 10 [10 -7 ] = -(-7) = 7 pH = -log 10 [10 -4 ] = -(-4) = 4pH = -log 10 [10 -2 ] = -(-2) = 2

40. pH and [ H + ] are Inversely Proportional pH = -log 10 [10 -7 ] = -(-7) = 7 pH = -log 10 [10 -4 ] = -(-4) = 4 pH = -log 10 [10 -2 ] = -(-2) = 2 fewer H + more H + higher pH lower pH pH = -log 10 [10 -12 ] = -(-12) = 12

41. 10 Fold Steps …each pH unit represents 10 fold difference in H + and OH - ions, …a solution of pH 3 is not twice as acidic as a solution of pH 6, …it is 10 3, or 1000 times more acidic, Small changes in pH represent large changes in H + and OH - concentrations.

43. Buffers …a solution characterized by the ability to resist changes in pH when limited amounts of acid or base are added to it,

44. Buffers Minimize pH Changes

45. To Do Read through pp. 48-55, as assigned in the syllabus, Note, for Tuesday, read pp. 58-60.