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Chapter 3: Water & Life. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A view of earth from space, showing our planet’s abundance.

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Presentation on theme: "Chapter 3: Water & Life. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A view of earth from space, showing our planet’s abundance."— Presentation transcript:

1 Chapter 3: Water & Life

2 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A view of earth from space, showing our planet’s abundance of water

3 Concept 3.1: Polar covalent bonds in water molecules result in hydrogen bonding The water molecule is a polar molecule: the opposite ends have opposite charges Polarity allows water molecules to form hydrogen bonds with each other © 2011 Pearson Education, Inc.

4 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 3.2 Hydrogen bonds between water molecules Hydrogen bonds  + + ++ H H ++ ++ –– –– –– ––

5 Concept 3.2: Four emergent properties of water contribute to Earth’s suitability for life Four of water’s properties that facilitate an environment for life are –Cohesive behavior –Ability to moderate temperature –Expansion upon freezing –Versatility as a solvent © 2011 Pearson Education, Inc.

6 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Water transport in plants (cohesion) Water conducting cells 100 µ m

7 Surface tension is a measure of how hard it is to break the surface of a liquid Surface tension is related to cohesion © 2011 Pearson Education, Inc.

8 Figure 3.4

9 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Water needs to give away energy in form of heat when it goes from gas to liquid, and from liquid to solid. The opposite is also true: water needs to take energy in form of heat when going from solid to liquid or liquid to gas. Water is special in its need to absorb or expend a LARGE AMOUNT of heat to change form. The latter is the reason we perspire: evaporating water cools down our skin. Water’s Ability to Moderate Temperature

10 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ice: crystalline structure and floating barrier Liquid water Hydrogen bonds constantly break and re-form Ice Hydrogen bonds are stable Hydrogen bond

11 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A crystal of table salt dissolving in water (use as a solvent) 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 –

12 Water: The Solvent of Life A solution is a liquid that is a homogeneous mixture of substances A solvent is the dissolving agent of a solution The solute is the substance that is dissolved An aqueous solution is one in which water is the solvent © 2011 Pearson Education, Inc.

13 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Reaction producing hydroxide and hydronium ions H Hydronium ion (H 3 O + ) H Hydroxide ion (OH – ) H H H H H H + – +

14 Figure 3.10 pH Scale Battery acid Gastric juice, lemon juice Vinegar, wine, cola Beer Tomato juice Black coffee Rainwater Urine Saliva Pure water Human blood, tears Seawater Inside of small intestine Milk of magnesia Household ammonia Household bleach Oven cleaner Basic solution Neutral solution Acidic solution Neutral [H + ] = [OH  ] Increasingly Basic [H + ] < [OH  ] Increasingly Acidic [H + ] > [OH  ] H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ OH  H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H

15 Acidification: A Threat to Water Quality Human activities such as burning fossil fuels threaten water quality CO 2 is the main product of fossil fuel combustion About 25% of human-generated CO 2 is absorbed by the oceans © 2011 Pearson Education, Inc.

16 The burning of fossil fuels is also a major source of sulfur oxides and nitrogen oxides These compounds react with water in the air to form strong acids that fall in rain or snow Acid precipitation is rain, fog, or snow with a ph lower than 5.2 Acid precipitation damages life in lakes and streams and changes soil chemistry on land © 2011 Pearson Education, Inc.

17 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 3.9 Acid precipitation and its effects on a forest More acidic Acid rain Normal rain More basic


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