Water, Polarity, etc.

1. 1 Water and the Fitness of the Environment

2. 2 Importance of water Overview: The Molecule That Supports All of Life Water is the biological medium here on Earth All living organisms require water more than any other substance

3. 3 Water Facts The polarity of water molecules results in hydrogen bonding The water molecule is a polar molecule

4. 4 – Hydrogenbonds + H – + H + –  – + Figure 3.2 Water’s Polarity The polarity of water molecules Allows them to form hydrogen bonds with each other Contributes to the various properties water exhibits

5. 5 Properties of water Water conducting cells Four emergent properties of water contribute to Earth’s fitness for life 3. Water moderates air temperature because it has a high specific heat, which allows it to minimize temperature fluctuations to within limits that permit life 1. Cohesion - Like molecules bonding to each other (water attracting other water molecules) 2. Surface tension Is a measure of how hard it is to break the surface of a liquid 4. Water is a versatile solvent due to its polarity

6. 6 Insulation of Bodies of Water by Floating Ice Solid water, or ice Is less dense than liquid water Floats in liquid water Life can exist under the frozen surfaces of lakes and polar seas

7. 7 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 The different regions of the polar water molecule can interact with ionic compounds called solutes and dissolve them

8. 8 Hydrophilic and Hydrophobic Substances A hydrophobic substance Does not have an affinity for water A hydrophilic substance Has an affinity for water

9. 9 Acids and Bases Dissociation of water molecules leads to acidic and basic conditions that affect living organisms Organisms must maintain homeostasis in the pH of their internal and external environments

10. 10 + – H H H + H H H H H Hydroxide ion (OH–) Hydronium ion (H3O+) Figure on p. 53 of water dissociating Effects of Changes in pH Water can dissociate Into hydronium ions (H+ or H3O+)and hydroxide (OH-) ions Changes in the concentration of these ions Can have a great affect on pH in living organisms

11. 11 Acids and Bases An acid Is any substance that increases the hydrogen ion concentration of a solution A base Is any substance that reduces the hydrogen ion concentration of a solution

12. 12 The pH Scale Scale goes from 0-14 with 7 neutral The pH of a solution Is determined by the relative concentration of hydrogen ions Difference of 10X in hydrogen ion concentration between any two pH values Acids have a higher number of H+ ions than a base Acids produce H+ ion in solution Bases produce OH- ions in solution

13. 13 The pH scale and pH values of various aqueous solutions pH Scale 0 1 Battery acid 2 Digestive (stomach) juice, lemon juice Vinegar, beer, wine, cola 3 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 Increasingly Basic [H+] < [OH–] Milk of magnesia 11 Household ammonia 12 Household bleach 13 Oven cleaner 14 Figure 3.8

14. 14 Buffers The internal pH of most living cells Must remain close to pH 7 Buffers Are substances that minimize changes in the concentrations of hydrogen and hydroxide ions in a solution Consist of an acid-base pair that reversibly combines with hydrogen ions Made by organisms

15. 15 0 1 Moreacidic 2 3 Acidrain 4 5 Normalrain 6 7 8 9 10 11 12 13 Morebasic 14 Figure 3.9 Acid precipitation Can damage life in Earth’s ecosystems

16. 16 Moles and Molarity A mole Represents an exact number of molecules of a substance in a given mass Molarity Is the number of moles of solute per liter of solution

17. 17 God created water before life 1 In the beginning God created the heavens and the earth. 2 Now the earth was formless and empty, darkness was over the surface of the deep, and the Spirit of God was hovering over the waters.