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Cuthbert Heath
6 years ago
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2 Important properties of liquid water (H 2 O) compared with those of n-pentane (C 5 H 12 ), another liquid at room temperature. Property Water n-pentane Boiling point ( C) Heat of vaporization (kj/g) Melting point ( C) Heat of fusion (kj/g) Dielectric constant Surface tension (dyne/cm) Specific heat (J/g/ C) Why are the values for water so much higher? 2

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5 Textbook examines: (1) Water s cohesive (and adhesive) behavior and high surface tension (all due to ); (2) Water s ability to stabilize ambient temperature (due to ) and provide evaporative cooling (due to ); (3) Water s expansion upon freezing (due to ); and (4) Water s versatility as a solvent (due to ). 5

6 460 kj/mol 18.8 kj/mol 11

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8 Fig. 3-4 Results of high surface tension 13

9 Water s ability to stabilize (moderate a change in ambient) air temperature 14

10 Water s expansion upon freezing 15

11 Liquid water Ice 16

Water vapor Ice Liquid water http://www.chem1.

html Density of water (ρ W ) ºC ρ W (g/cm 3 ) 0

12 Water vapor Ice Liquid water Density of water (ρ W ) ºC ρ W (g/cm 3 ) 0 (solid) (liquid)

13 Water s versatility as a solvent 18

14 F is the value in Newtons (N) of the attractive or repulsive force between two ions e 1 and e 2 are the charges of the respective ions r is the distance between e 1 and e 2 ε 0 is the permittivity constant (= C 2 /(N m 2 )) ĸ is the dielectric constant of the medium in which the ions are found (78.54 for water versus 1.84 for n-pentane) 19

15 What is the effect on the attractive force (F) between two ions of opposite charge when: a calcium ion replaces a sodium ion as e 1? the two ions move twice as far apart? the solvent is replaced with one that has a dielectric constant twice the value of the one it replaced? 20

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17 Colligative properties of water (depend on the total number of solute particles per unit volume of solvent) Freezing point Boiling point Vapor pressure Osmotic potential ( with solute concentration) ( with solute concentration) ( with solute concentration) ( with solute concentration) The most important biologically 22

18 W S P ( ) M g Matric potential Gravitational potential Pressure potential Osmotic potential (Solute potential) Water potential (chemical potential of water) Water always moves from an area of higher water potential (free water concentration) to an area of lower water potential (free water concentration), as long as there is a pathway. 23

19 W P S g M S g c RT S gh W mirt Density of water (ρ W ) ºC ρ W (g/cm 3 ) 0 (solid) (liquid)

20 Osmosis 25

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22 Figure not in current edition of text. 27

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26 Bulk flow by positive pressure 31

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28 H 2 O H + + OH - K eq [ H ] eq [ H [ OH 2 O] eq ] eq 1000 g / l [ H O] 55. 5M 2 18g / mol [ H ] [ OH ] 110 M 55. 5M 7 K 55.5M [ H ][ OH ] eq 33

29 K eq K 55.5 K eq W K W [ H ][ OH ]

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31 Some carbon dioxide (CO 2 ) in the atmosphere dissolves in the ocean, where it reacts with water to form carbonic acid (H 2 CO 3 ). Carbonic acid (H 2 CO 3 ) dissociates into hydrogen cations (H + ) and bicarbonate anions (HCO 3- ). The added hydrogen cations (H + ) combine with carbonate anions (CO 3 2- ), forming more HCO 3-. Fewer carbonate anions (CO 3 2- ) are available for calcification the formation of calcium carbonate (CaCO 3 ) by marine organisms such as corals. 36

32 CH COOH H O CH COO H O ph pk a log base acid eq eq ph pk a log CH COO 3 CH COOH 3 eq eq If ph = 7.00 and pk a = 4.75, what is the ratio of acetate anion to acetic acid in dilute solution? Is the acetic acid mostly dissociated? 37

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34 Technique Description 1. Elaborative interrogation Generating an explanation for why an explicitly stated fact or concept is true (tends to be content rich) 2. Self-explanation Explaining how new information is related to known information, or explaining steps taken during problem solving (tends to be content free) 3. Summarization Writing summaries of to-be-learned texts 4. Highlighting/Underlining Marking potentially important portions of to-be-learned materials while reading 5. Keyword mnemonic Using keywords and mental imagery to associate verbal materials 39

35 Elaborative interrogation encompasses: generating an explanation for an explicitly state fact; asking why some fact, process, event, et cetera, makes sense and generating a (reasonable) answer that explains it; integrating new information into existing knowledge; articulating similarities and differences between situations; constructing concept maps to clarify the relationships among terms and concepts. For a short explanation of this method and a blood-related example, see For an example of a concept map created for bonding, see 992_18229/Bonding%20Unit%202.cmap 40

8/27/2017. Why are the values for water so much higher? 2

8/27/2017. Why are the values for water so much higher? 2 http://www.n4jbp.com/hawaii/pics/ocean.jpg 1 Important properties of liquid water (H 2 O) compared with those of n-pentane (C 5 H 12 ), another liquid at room temperature. Property Water n-pentane Boiling