1. Chapter 3

2. It’s pretty important… Life probably evolved in water Cells are 70% to 90% water Water covers ¾ of the earth’s surface It naturally exists in all 3 states HOW MANY THINGS CAN YOU SAY ALL THAT ABOUT????

3. Water is polar, which is pretty cool! It results from the polar covalent bond between the elements, hydrogen and oxygen. Each H2O molecule can bond with 4 other water molecules due to its unequal charge. What type of bond is that?Hydrogen Bond 1 2 3 4

4. Properties of polarity - Cohesion COHESION – the ability of H2O molecules to stick together (their attraction). Also, part of the reason for capillary action. Adhesion – the ability to adhere to another surface. (kind of like Van der Waals interactions) Surface Tension – the measure of how hard it is to break the surface of water. (like a water skimmer, or drops of water on a penny)

5. Properties of polarity - Temperature High Specific Heat – the amount of energy it takes to raise the temp. by 1 o Celsius. Water is 1cal/g/ o C Why don’t oceans vary in temperature that much? Evaporative Cooling – since water has a high heat of vaporization, once water leaves the surface, the surface cools down. What homeostatic mechanism does this for us? Sweating Cools us down!!!

6. Ice Floats!!!! So what, big deal, right? …….. WRONG!!!! Water is less dense as a solid 0 o C; it is most dense at 4 o C! HUH? Well at 4 0 it has contracted the most, then from 4 o to 0 o it begins expanding and is less dense, hence the floating. This acts as insulation to prevent freezing of deep bodies of water!!!

7. Universal Solvent Solvent – water is the universal solvent since ionic and polar compounds both dissolve in it. (hydrophilic) Hydrophbic compounds do not dissolve in water, ex. lipids Solute – the stuff dissolved in a solvent Solution – solvent +solute Aqueous Solution – a solution in which water is the solvent. Express in Molarity. See next slide…

8. ….. Measure out a mole of sucrose. Calculate the molecular weight of C 12 H 22 O 11 C = 12 dal, H = 1 dal, O = 16 dal x12 x22x11 _________________________________________ 144 dal22dal176dal = 342 dal or 342g Now to make a 1M sucrose sol’n, weight out 342 g of sucrose and add water up to 1L. TA DAA! (this is useful for AP Lab #1 Osmosis and Diffusion)

9. Don’t forget pH Water dissociates into H + and OH - ions! Acids 0 – >7 Bases <7 - 14 Distilled water is neutral, is tap water??? Buffers, ex. Carbonic acid, HCl, NaOH

10. Science, Technology, and Society Acid Rain has been recorded as low as 1.5 in West Virgina. Result of Sulfur Dioxide and nitrogen oxides react with water in the air to form acids. Where do the sulfurs and nitrogen oxides come from? What do they do to the Environment?