Chapter: 3 Water
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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chapter: 3 Wate
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Chapter: 3 Water. Figure 3.1. Water: A Molecule That Supports All of Life. 3/4 of the Earth’s surface Abundance is the main reason the Earth is habitable. –. +. Hydrogen bonds. H. –. +. H. +. –. –. +. Figure 3.2. Polar Nature of Water. Oxygen Highly electro negative - PowerPoint PPT Presentation
Transcript of Chapter: 3 Water
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Chapter: 3 Water
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Water: A Molecule That Supports All of Life
• 3/4 of the Earth’s surface
• Abundance is the main reason the Earth is habitable
Figure 3.1
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Hydrogenbonds
+
+
H
H+
+
–
–
– –
Figure 3.2
Polar Nature of Water• Oxygen Highly electro negative• Polarity of water molecules
Hydrogen bonds between molecules
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Properties of Water
• Cohesion: Capillary Action
• High Specific Heat: Moderation of Temperature
• Ice Floats
• Universal Solvent
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Cohesion
• Bonding to neighboring molecules
• Due to hydrogen bonding
Hydrogenbonds
+
+
H
H+
+
–
–
–
–
Figure 3.2
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Cohesion
• Transpiration pull water up through the microscopic vessels of plants
Water conducting cells
100 µmFigure 3.3
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Cohesion
• Surface tension
Figure 3.4
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Water moderates air temperature
• Absorbs heat from air that is warmer and releasing the stored heat to air that is cooler
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Water High Specific Heat
• Amount of heat absorbed or lost to change its temperature
hydrogen bonds
• Evaporative Cooling: Sweat
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Ice Floats
• Hydrogen bonds in ice
– More “ordered” than in liquid water less dense
Liquid waterHydrogen bonds
constantly break and re-form
IceHydrogen bonds are stable
Hydrogen bond
Figure 3.5
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Ice Floats
Water is most dense at 4 deg. C•Because ice floats in water life can exist under the frozen surfaces of lakes and polar seas
1.0g/cm3= liquid0.9g/cm3= ice
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Solvent of Life
• Polar regions of water molecule interact with ionic compounds
Negative oxygen regions
of polar water molecules are attracted to sodium
cations (Na+).+
+
+
+Cl –
–
–
–
–
Na+Positive hydrogen regions
of water molecules cling to chloride anions
(Cl–).
++
+
+
–
–
–
–
–
–Na+
Cl–
Figure 3.6
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Water: Solvent of Life
• Hydophilic
• HydrophobicBenzene
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Solute Concentration
• Molecular Mass: Sum of the masses of all the atom in a molecule
• Avogadro's Numbe: 6.0 x 10-23 Daltons= 1g
• Molar Mass: molecular mass x Avogadro’s # (usually on chemical label) (moles)
• Molarity : The number of moles of solute per litter of solution.
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Examples
• If you have 5 M of a solute in 2.5 L of solution what is the molarity of the solution?
• The Concentration of a solute in blood is 1.3 x10-10 M. How many molecules of this solute would be in a liter of blood?
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What is pH?
Hydronium concentration in water is 10-7. pH is –log of H+ concentrationAcids increase H+ concentrationBases reduce H+ concentrationAcidic = Higher H+
Basic = Higher OH-
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pH scale
Incr
easi
ngly
Aci
dic
[H+ ]
> [O
H– ]
Incr
easi
ngly
Bas
ic[H
+ ] <
[OH
– ]
Neutral[H+] = [OH–]
Oven cleaner
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
pH Scale
Battery acid
Digestive (stomach) juice, lemon juiceVinegar, beer, wine,colaTomato juice
Black coffee RainwaterUrine
Pure waterHuman blood
Seawater
Milk of magnesia
Household ammonia
Household bleach
Figure 3.8
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Buffers
• Minimize changes in pH
• Carbonic acid in the blood
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http://www.youtube.com/watch?v=V3NCeSlYQWQ&feature=player_detailpage
Chapter 4: Carbon Compounds
A fat molecule
