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Chapter: 3 Water

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

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Chapter: 3 Water

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  1. Chapter: 3 Water

  2. 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

  3. – + Hydrogenbonds H – + H + –  – + Figure 3.2 Polar Nature of Water • Oxygen Highly electro negative • Polarity of water molecules  Hydrogen bonds between molecules

  4. Properties of Water • Cohesion: Capillary Action • High Specific Heat: Moderation of Temperature • Ice Floats • Universal Solvent

  5. – + Hydrogenbonds H – + H + –  – + Figure 3.2 Cohesion • Bonding to neighboring molecules • Due to hydrogen bonding

  6. Water conducting cells 100 µm Figure 3.3 Cohesion • Transpiration pull water up through the microscopic vessels of plants

  7. Figure 3.4 Cohesion • Surface tension

  8. Water moderates air temperature • Absorbs heat from air that is warmer and releasing the stored heat to air that is cooler

  9. Water High Specific Heat • Amount of heat absorbed or lost to change its temperature •  hydrogen bonds • Evaporative Cooling: Sweat

  10. Hydrogen bond Liquid water Hydrogen bonds constantly break and re-form Ice Hydrogen bonds are stable Figure 3.5 Ice Floats • Hydrogen bonds in ice • More “ordered” than in liquid water less dense

  11. 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= liquid 0.9g/cm3= ice

  12. Negative oxygen regions of polar water molecules are attracted to sodium cations (Na+). – Na+ + + – + – – Positive hydrogen regions of water molecules cling to chloride anions (Cl–). Na+ – + + Cl – Cl– + – – + – + – – Figure 3.6 Solvent of Life • Polar regions of water molecule interact with ionic compounds

  13. Water: Solvent of Life • Hydophilic • Hydrophobic Benzene

  14. 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.

  15. 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?

  16. What is pH? Hydronium concentration in water is 10-7. pH is –log of H+ concentration Acids increase H+ concentration Bases reduce H+ concentration Acidic = Higher H+ Basic = Higher OH-

  17. pH Scale 0 1 Battery acid 2 Digestive (stomach) juice, lemon juice 3 Vinegar, beer, wine, cola Increasingly Acidic [H+] > [OH–] 4 Tomato juice 5 Black coffee Rainwater 6 Urine Neutral [H+] = [OH–] 7 Pure water Human blood 8 Seawater 9 10 Milk of magnesia Increasingly Basic [H+] < [OH–] 11 Household ammonia 12 Household bleach 13 Oven cleaner 14 Figure 3.8 pH scale

  18. Buffers • Minimize changes in pH • Carbonic acid in the blood

  19. A fat molecule Chapter 4: Carbon Compounds http://www.youtube.com/watch?v=V3NCeSlYQWQ&feature=player_detailpage

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