1. Properties of Water and pH Section 2-2 Notes Lab

2. Covers three fourths of our planet Covers three fourths of our planet Most abundant compound in living things Most abundant compound in living things Liquid at room temp Liquid at room temp Expands as it freezes Expands as it freezes Lighter than most gases Lighter than most gases Moderates temperatures by storing heat Moderates temperatures by storing heat Water – an unusual compound

3. Water = H 2 O Covalent bonds hold the molecule together Covalent bonds hold the molecule together Electrons are shared unequally Electrons are shared unequally Oxygen takes most of the negative charge Oxygen takes most of the negative charge Hydrogen atoms are left slightly positive Hydrogen atoms are left slightly positive

4. Polarity Molecule has a positive side and a negative side Molecule has a positive side and a negative side –Due to unequal sharing of electrons Weak bonds form Weak bonds form –Called: hydrogen bonds

5. Polarity These weak hydrogen bonds are important These weak hydrogen bonds are important Causes water to attract other molecules Causes water to attract other molecules Water’s hydrogen can bond with up to 4 other molecules Water’s hydrogen can bond with up to 4 other molecules

6. Water has special properties due to hydrogen bonding Cohesion – attraction between water molecules Cohesion – attraction between water molecules –Surface tension –Flow of water Adhesion – attraction between water and other molecules Adhesion – attraction between water and other molecules –Water sticking to windshield Capillary action – movement of water against the pull of gravity Capillary action – movement of water against the pull of gravity –Within plant stems

7. Ionization Any process by which electrically neutral atoms or molecules are converted to electrically charged atoms or molecules (ions). Any process by which electrically neutral atoms or molecules are converted to electrically charged atoms or molecules (ions). Causes molecules to separate into simpler molecules, atoms, or ions Causes molecules to separate into simpler molecules, atoms, or ions Water attracts other ions Water attracts other ions –Conduction of nerve impulses –Contraction of muscles –Digestion of food

8. Ionization of Water

9. An Acid has more H+ ions than OH- ions. An Acid has more H+ ions than OH- ions. A base has more OH- ions than H+ ions. A base has more OH- ions than H+ ions. A neutral solution has an equal number of each. A neutral solution has an equal number of each. H+H+H+H+OH- H+ OH-OH-OH-OH- H+H+H+H+ OH-OH-OH-OH-

10. pH = “Power of Hydrogen Ion” Indicates the concentration of H + ions in solution Indicates the concentration of H + ions in solution Range = 0 – 14 Range = 0 – 14 pH 7 = neutral pH 7 = neutral Each pH is 10x the concentration of the previous Each pH is 10x the concentration of the previous

11. pH = “Power of Hydrogen Ion” Example: Example: –Change in pH from 10 to 12 –concentration change equals… –10 x 10 or… – 100

12. Acids vs. Bases ACIDSBASES pH 7 Sour tastetaste bitter more H + ionsmore OH - ions

13. pH Scale Acid Base 0714 [H + ] pH 10 -14 14 10 -13 13 10 -12 12 10 -11 11 10 -10 10 10 -9 9 10 -8 8 10 -7 7 10 -6 6 10 -5 5 10 -4 4 10 -3 3 10 -2 2 10 -1 1 10 0 0 1 M NaOH Ammonia (household cleaner) Blood Pure water Milk Vinegar Lemon juice Stomach acid 1 M HCl Acidic Neutral Basic Most living organisms prefer a neutral pH range from 6.5-8.5. Most life dies in an environment of pH12 or higher.

14. Buffers Chemicals that neutralize small amounts of acids or bases Chemicals that neutralize small amounts of acids or bases Controls pH which is important to maintaining homeostasis Controls pH which is important to maintaining homeostasis Minimizes shifts in pH Minimizes shifts in pH Normal pH in humans is 6.5 – 7.5 Normal pH in humans is 6.5 – 7.5

15. Oven cleaner Bleach Ammonia solution Soap Sea water Human blood Pure water Normal rainfall Acid rain Tomato juice Lemon juice Stomach acid Neutral Increasingly Basic Increasingly Acidic Milk Sodium hydroxide Lye Asprin Intestinal fluid Cola Battery acid Baking soda Milk of Magnesia Urine Spinach Tums

16. Mixture 2 or more elements or compounds mixed together NOT chemically combined e.g. –S–S–S–Soil –A–A–A–Air –S–S–S–Salt water

17. Two types of mixtures 1. Solution: 1 or more dissolved chemicals Solvent – chemical that others dissolve in Solvent – chemical that others dissolve in Solute – chemical that is dissolved Solute – chemical that is dissolved Water is the best solvent!!! Water is the best solvent!!! Aqueous solutions – solutions of water Aqueous solutions – solutions of water Cl - Water Cl - Na + Water Na +

18. 2. Suspensions Substances mixed in water, but not dissolved Substances mixed in water, but not dissolved Molecules are “suspended” in the water Molecules are “suspended” in the water e.g. e.g. –Blood contains proteins and cells –Cytoplasm contains organelle Blood Cytoplasm

19. Importance of Water to Living Organisms Most abundant compound in living matter Most abundant compound in living matter Universal solvent - dissolves many things Universal solvent - dissolves many things Needed for biological (metabolic) reactions Needed for biological (metabolic) reactions Transports materials Transports materials Regulates temperature Regulates temperature Needed to eliminate wastes Needed to eliminate wastes Protects and cushions vital organs Protects and cushions vital organs Lubricates joints and tissues Lubricates joints and tissues Reservoir of H + and OH - ions Reservoir of H + and OH - ions