2. Chapter 3 WATER AND THE FITNESS OF THE ENVIRONMENT Themes: 1.Emergent Properties 2.Structure and Function 3.Science, Technology and Society

3. Objectives: Polarity of water molecules Cohesion of water Water moderates temperature on Earth Ice floats… why? Solvent of life Organisms are sensitive to pH changes Acid Rain

4. Root Words: Kilo – Hydro – - philos - phobos

5. Hydrogen Bonding is the Most Important Concept: Most of water’s characteristics are due to the principle of hydrogen bonding. - + + + +

6. Formation of hydrogen bonds - Releases heatFormation of hydrogen bonds - Releases heat Breaking of hydrogen bonds - Absorbs heatBreaking of hydrogen bonds - Absorbs heat Cohesion - hydrogen bonds holding water molecules together, helps water move up a tree. Surface tension - cohesion Beading of water – cohesion Water’s high heat of evaporation is due to hydrogen bonding.Water’s high heat of evaporation is due to hydrogen bonding. Heat of Vaporization - quantity of heat a liquid must absorb for 1 gm of water to be converted from liquid to a gas.

7. Specific heat - amt. of heat that must be absorbed or lost by 1gm. Of a substance to change it’s temp. 1° C. Water is 1cal/g/1°C. Water has high specific heat compared to other substances, thus it resists changes in temp. when it absorbs or releases heat. Water also has high boiling point.

8. ICE - Water expands when it freezes. Ice is less dense than liquid water. WHY??? NOTE - hydrogen bonding causing less H 2 0/vol

9. A CRYSTAL OF TABLE SALT DISSOLVING IN WATER. The H+ regions of the polar water molecules are attracted to the chloride anions (green), the O- regions cling to the sodium cations (yellow). The sphere of water molecules surrounding a solute ion (or molecule) is called a hydration shell.

10. HYDROPHILIC - “WATER LOVING” SUBSTANCES THAT HAVE AN AFFINITY FOR WATER EVEN IF THEY DO NOT DISSOLVE IN WATER. (IONIC OR POLAR MOLECULES). HYDROPHOBIC - “WATER FEARING” WILL NOT DISSOLVE IN WATER OR HAVE NO AFFINITY FOR WATER. (NON-IONIC, NONPOLAR SUBSTANCES)

11. CALORIES & KILOCALORIES: Calories = amt. of heat needed to raise 1 gm. of water 1 ° C. Kilocalorie = 1000 calories. If 10 ml of water was raised 1 ° C this would be 10 calories.

12. MAKING AQUEOUS SOLUTIONS: To make a solution - dissolve solute in small amt. of water THEN add water to get the final volume. A mole is = in number to mol. weight of a substance in grams. Molecular weight = sum of weights of all atoms in a molecule. EXAMPLE - C 2 H 5 O 2 NH 2 mol. Wt. : H =7; O = 32; N= 14; C = 24 (77)

13. MOLARITY - # of moles of solute per liter of solution. 77 g of solute in 1 liter of water = 1 M solution. 7.7 g of solute in 1 liter of water = 0.1 M solution. REMEMBER - you are attempting to keep the same proportion of solute to solvent in the solution.

14. ACIDS, BASES & BUFFERS: ACIDS: H + (proton) donors in aqueous solution (increase H + ions in solution.) BASE : H + (proton) acceptor in aqueous solution (reduces in H + ions in solution.). Also reduce H + ions indirectly by dissociating to form OH - ions (combine with H + to form H 2 O). Aqueous - of, like, or containing water; watery

15. pH Scale:pH Scale: -log [H] & is a ten fold difference between whole #’s. EXAMPLE: pH 6 to pH 5 = 10 times increase in acidity. EXAMPLE: pH 6 to 4 = 100 times increase in acidity. 0 1 2 3 4 5 6 (Strong acid) (med. acid) (weak acid)

16. pH Scale - [H + ] [OH - ] = 10 -14pH Scale - [H + ] [OH - ] = 10 -14 pH 7 [H + ] -7 [OH] -7 = 10 -14pH 7 [H + ] -7 [OH] -7 = 10 -14 pH 6 [H + ] -6 [OH] -8 = 10 -14pH 6 [H + ] -6 [OH] -8 = 10 -14 Common acids - lemon juice, vinegar, coffee. Common bases - seawater(pH8) ammonia, bleach.

17. DO ALL SUBSTANCES HAVE MEASURABLE pH? NO !!!!! Why??? Substance must dissolve in water (dissociate in water). EXAMPLES: Hydrocarbons which are nonpolar - gasoline, kerosene, butane, methane.

18. BUFFERS: Chemicals that minimize changes in pH by: Accepting H + OR release H + ions (acid solution) ( basic solution) NOTE: Bases are also called alkaline.

19. Even a molecule as large as a protein can dissolve in water if it has enough ionic and polar regions on its surface. The mass of purple here represents a single such molecule,which water molecules are surrounding. WATER-SOLUBLE PROTEINWATER-SOLUBLE PROTEIN