Chapter 3 Water and the Fitness of the Environment PowerPoint Lectures for Biology Eighth Edition Neil Campbell and Jane Reece Water s Polarity The polarity of water molecules Allows them to form hydrogen bonds with each other Contributes to the various properties water exhibits that makes it so suitable to supporting life Hydrogen bonds H Figure 3 2 H Cohesion and Adhesion Helps pull water up through the microscopic vessels of plants Adhesion Water conducting cells Direction of water movement Cohesion 150 m Surface tension Is a measure of how hard it is to break the surface of a liquid Is related to cohesion Figure 3 4 Moderation of Temperature Water moderates air temperature By absorbing heat from air that is warmer and releasing the stored heat to air that is cooler Los Angeles Airport 75 70s F 80s 90s 100s Fig 3 5 San Bernardino 100 Riverside 96 Santa Ana Palm Springs 84 106 Burbank 90 Santa Barbara 73 Pacific Ocean San Diego 72 40 miles Insulation of Bodies of Water by Floating Ice The hydrogen bonds in ice Are more ordered than in liquid water making ice less dense Hydrogen bond Figure 3 6 Ice Liquid water Hydrogen bonds are stable Hydrogen bonds constantly break and re form The Solvent of Life 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 7 Water can also interact with polar molecules such as proteins This oxygen is attracted to a slight positive charge on the lysozyme This hydrogenmolecule is attracted to a slight Figure 3 8 a Lysozyme molecule in a nonaqueous environment b Lysozyme molecule purple in an aqueous environment such as tears or saliva negative charge on the lysozyme molecule c Ionic and polar regions on the protein s Surface attract water molecules Dissociation of Water Molecules H H H H Figure on p 52 of water dissociating H H H Hydronium ion H3O Simplified Process H2O water H Hydrogen ion H Hydroxide ion OH OHHydroxide ion The pH Scale pH Scale 0 H H H H OH OH H H H H Acidic solution Increasingly Acidic H OH The pH scale 0 14 and pH values of various aqueous solutions 1 Battery acid Gastric juice 2 lemon juice 3 Vinegar beer wine cola 4 Tomato juice 5 Black coffee Rainwater 6 Urine OH OH H H OH OH OH H H H Neutral H OH 8 Seawater OH OH H OH OH OH H OH Basic solution Fig 3 9 Increasingly Basic H OH Neutral solution OH Saliva 7 Pure water Human blood tears 9 10 Milk of magnesia 11 Household ammonia 12 Household 13 bleach Oven cleaner 14 Acid precipitation Can damage life in Earth s ecosystems 0 1 2 More acidic 3 4 Acid rain 5 6 Normal rain 7 8 9 10 11 12 13 14 Figure 3 10 More basic You should now be able to 1 List and explain the four properties of water that emerge as a result of its ability to form hydrogen bonds 2 Distinguish between the following sets of terms hydrophobic and hydrophilic substances a solute a solvent and a solution mole molar concentration 3 Define acid base and pH 4 Explain how buffers work Copyright 2008 Pearson Education Inc publishing as Pearson Benjamin Cummings
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