1. Chapter 3: water!

2. 1. Water’s polarity results in Hydrogen bonding H bond: attraction b/t an O (or N) on one molecule, and an H on a DIFFERENT molecule – Weak, temporary When they break (e.g. boiling water) : is energy absorbed, or produced? What happens to energy when they form (i.e. condensation)

3. 2. H2O can make 4 H bonds More than most liquids TO DO: diagram a water molecule From http://nrich.maths.org/7273http://nrich.maths.org/7273

4. 3. Surface tension Liquid mountaineering – a method of running ON water but not sinking in. From http://www.youtube.com/watch? v=Oe3St1GgoHQ http://www.youtube.com/watch? v=Oe3St1GgoHQ

5. 4. thermal, cohesive and solvent properties of water Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Cohesion – H bonds! Surface tension Ice floats High heat capacity High heat of vaporization

6. 5. Cohesion: H2O’s stick together b/c water makes MORE H bonds (4) than most liquids

7. 6. Water makes so many H bonds (4). Result: properties…. Property of water Description & importance to life How H bonds make it work Surface tension High Heat of vapor- ization High specific heat Ice floatsOceans don’t freeze solid

8. 7. Water moderates temperature – high specific heat capacity (define – p. 48) San Diego 72° 40 miles Pacific Ocean 70s (°F ) 80s 90s 100s Santa Barbara 73° Los Angeles (Airport) 75° Burbank 90° San Bernardino 100° Riverside 96° Santa Ana 84° Palm Springs 106°

9. 8. Water is a Solvent, so is a medium for chemical reactions Video clip: “water dissolves salt”. What part of the water molecule dissolves Na+? What part dissolves CL- ?

10. 9. 3D animation of ice & water 1. Go to: http://www.edinformatics.com/interac tive_molecules/water.htm http://www.edinformatics.com/interac tive_molecules/water.htm – Go thru the “water” lesson, Q #1: why is water a good solvent? 2. Click on “water molecule” below the model, scroll to “water is highly cohesive”, and click on “Click here or on the image to your left to view…”here Q #2: what does the movie show you about H bonds? – Mac users: for “right click”, hold down Control key & click. – Click on “style”, then “Scheme”, then “CPK spacefill”, or “Label” etc.

11. 10. ice Click on “Ice” in the right column. Q #3: why does ice float? To answer this: – Do the “Try this” for ice (“CPK spacefill” etc.) then for water Q #4: Write down the differences you see between liquid water and ice. Q #5: how many H bonds does a liquid water molecule make? How about an ice water molecule? Go back and answer question 3 now.

13. 11. Practice In groups, figure out how to model the properties of water, referring to H bonds. One narrator, other actors Solvent: one NaCl, 3 water molecules, narrator Evaporative Cooling: one hot animal, 4 water mol’s, 1 narrator Ice formation: 4 waters, 1 narrator Transport: wall is plant vessel (xylem), 3 waters, 1 Mg++, 1 narrator. Show movement, adhesion, cohesion, transport of Mg++.

14. 12. Acids & Bases ISSUE: pH of living tissue must be close to pH 7 (your blood is between 7.2 and 7.4) Acids: hi [H+] – ___ pH (“hi” or “lo”) Bases: lo [H+] – ___ pH

15. Assessment 1. explain how the polarity of the water molecule is important in evaporative cooling; Key: – 1. 4 H bonds by each H2O – 2. body heat breaks H bonds of sweat – 3.