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

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Hydrogen bonds + + H H + +  – –  – –  – –  – – Figure 3.2 Polar Nature of Water Oxygen Highly electro negative Polarity of water molecules  Hydrogen bonds between molecules

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Properties of Water Cohesion: Capillary Action High Specific Heat: Moderation of Temperature Ice Floats Universal Solvent

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cohesion Bonding to neighboring molecules Due to hydrogen bonding Hydrogen bonds + + H H + +  – –  – –  – –  – – Figure 3.2

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cohesion Transpiration  pull water up through the microscopic vessels of plants Water conducting cells 100 µ m Figure 3.3

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cohesion Surface tension Figure 3.4

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Water moderates air temperature Absorbs heat from air that is warmer and releasing the stored heat to air that is cooler

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Water  High Specific Heat Amount of heat absorbed or lost to change its temperature  hydrogen bonds Evaporative Cooling: Sweat

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ice Floats Hydrogen bonds in ice – More “ordered” than in liquid water  less dense Liquid water Hydrogen bonds constantly break and re-form Ice Hydrogen bonds are stable Hydrogen bond Figure 3.5

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 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/cm 3 = liquid 0.9g/cm 3 = ice

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 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

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Water: Solvent of Life Hydophilic Hydrophobic Benzene

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Solute Concentration Molecular Mass: Sum of the masses of all the atom in a molecule Avogadro's Numbe: 6.0 x 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.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 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?

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings What is pH? Hydronium concentration in water is pH is –log of H + concentration Acids increase H + concentration Bases reduce H + concentration Acidic = Higher H + Basic = Higher OH -

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings pH scale Increasingly Acidic [H + ] > [OH – ] Increasingly Basic [H + ] < [OH – ] Neutral [H + ] = [OH – ] Oven cleaner pH Scale Battery acid Digestive (stomach) juice, lemon juice Vinegar, beer, wine, cola Tomato juice Black coffee Rainwater Urine Pure water Human blood Seawater Milk of magnesia Household ammonia Household bleach Figure 3.8

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Buffers Minimize changes in pH Carbonic acid in the blood

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings _detailpage Chapter 4: Carbon Compounds A fat molecule