Today is Thursday, September 19 th , 2013

1. In This Lesson: Properties of Water (Lesson 5 of 9) Today is Thursday,September 19th, 2013 Pre-Class: What is it we are trying to find on Mars (besides possible life)? Why send all that [expensive] stuff there? And why is what we are trying to find important? http://upload.wikimedia.org/wikipedia/commons/thumb/6/67/Mars_Curiosity_video_msl20120810.ogv/mid-Mars_Curiosity_video_msl20120810.ogv.jpg

2. Today’s Agenda • Really quick bonding review. • Learn the main Properties of Water. • Do the Water Lab. • Where is this in my book? • Academic: P. 40 and following… • Honors: P. 24 and following…

3. Bonding Review • Turn to your neighbor and see if the two of you can describe the three kinds of bonds there are. • When you’re done, describe your feelings on your understanding of bonding with a thumb signal to me.

4. BondsIonic How to remember: Ions are selfish

5. BondsCovalent How to remember: covalent = cooperative

6. BondsHydrogen How to remember: Hydrogen bonds are strong bonds between molecules involving hydrogen. Just remember that.

7. Van der Waals Force

8. What To Do: • Bond Battleship • Report your result • Unit 1 Quiz Preparation Battleship • Do not report your result • Electron Configuration Matching (if time) • Return to seat • Leave your computer OPEN – you’ll get it later

9. Properties of Water • On the following slides you’re going to see a picture or video illustrating a property (or two) of water. • It’s your job to try and think of that property. • Remember, we’re talking about specific things water does that helps support life (even if it’s not obviously helping). • What to write down? • The scene # and your guess. • The following definition. • What not to do? • Talk. This should be done in silence.

10. Scene 1 • Water expands when it freezes, becoming less dense. • Most other things contract. • Because it is less dense, it can float in liquid water, and ice forms at the top of ponds and lakes instead of at the bottom. • Fish and other aquatic life can stay alive even if their body of water freezes in winter. http://static.howstuffworks.com/gif/ice-fishing-4a.jpg

11. Scene 2 • Water has adhesion– it sticks to other stuff. • Adhesion is the attractive force between unlike particles. • Water molecules can adhere (stick) to substances. • This allows small amounts of water, like water drops, to suspend themselves without falling. http://en.wikivisual.com/images/9/96/Water_drops_on_spider_web.jpg

12. Scene 3 • Water has cohesion– it sticks to itself. • Water molecules can cohere (stick) to other water molecules. • This also allows small amounts of water, like water drops, to suspend themselves without falling, or it allows water to “bead up” if it is not adhering to a surface. http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/bio%20101/bio%20101%20lectures/chemistry/water%20on%20a%20waxed%20car.JPG

13. Cohesion • Cohesion is the force of attraction between particles of the same kind. • In water, this ability is provided by H-bonds.

14. Cohesion in Space • If we eliminate gravity from the picture, we can really see how water behaves, particularly with regard to cohesion and adhesion. • In space, with no meaningful gravity, water is almost entirely bound by intermolecular forces. • Let’s take a look…

15. Scene 4 • Water has capillary action (not a new property). • Capillary action is adhesion and cohesion in a small tube, allowing the water to rise. • This is partially how water rises up plant roots and into stems and leaves. • THIS ONLY OCCURS IN TUBES! • Capillary action video! http://water.me.vccs.edu/courses/env211/changes/capillary.gif

16. Scene 5 • Water has surface tension (not a new property). • Surface tension is cohesion at the surface. • Water molecules at the surface bond together (weakly), allowing the surface to support light objects. • Many different living things can float, stand, or even run on water. http://www.sea-way.org/blog/JesusLizard_01.JPG

17. Scene 6 • Water cools when it evaporates. • Evaporative cooling means that as water goes from a liquid to a gas, it takes heat with it. The rest of the water or substance is cooled. • Animals pant or sweat, allowing water to evaporate and cool their skin. • http://www.colorado.edu/physics/2000/bec/evap_cool.html

18. Scene 7 • Water has a high boiling point. • Water takes a relatively long time to boil, which means it does not evaporate easily. • Heat buffer for the Earth. • Imagine if water boiled at only 100° instead of 212° - would life as we know it be possible? http://media-2.web.britannica.com/eb-media/88/78188-004-43BFD14F.jpg

19. Another way to look at this… • Ever notice how it may be 90° at the beach and yet the water’s never that warm? http://www.crestfire.com/images/wcboat.jpg

20. Scene 8 • Water is polar, so other polar molecules can dissolve in it or interact with it. • Water is often called the Universal Solvent for this reason. • We need a new slide for this one. http://www.thirdwayblog.com/images/1600/AlkaSeltzerFizz.jpg

21. Water is Polar • Let’s think of it this way. You tell me which of these two guys is gonna hold onto his electrons more… (draw them too) Meet Hydrogen – Poor guy’s only got one proton. OMG OXYGEN! 8 PROTONS!!!!!1

22. Polarity • Polarity is when atoms in a molecule don’t all “pull” on the shared electrons evenly. • In other words, when not all the atoms play nice. • Water is a polar molecule. • What does that mean? • For one, it has poles, like, you know, Earth.

23. In a diagram… …and all that’s left on the other end are the hydrogen protons, causing that end of the molecule to take on a positive charge… But…since oxygen is such a strong atom, it doesn’t share electrons nicely. There are 10 total electrons in the molecule. Meet water: (say hi) Having all that negative charge built up around oxygen causes that end of the molecule to take on a negative charge… This is the source of cohesion/surface tension, and why it hurts to do a belly-flop. …which causes neighboring water molecules to form hydrogen bonds with the first one. - - H H H H H H + + O O O + + - - - + + - - - - - - - -

24. Water is Polar • Because Oxygen has so many more protons, it pulls more stuff (electrons) toward it. • In other words, the Oxygen end of a water molecule becomes slightly negative because it’s holding all the electrons over there. • The Hydrogen end becomes more positive. http://www.school-for-champions.com/science/images/static_induction-polar_h2o.gif

25. Water is Polar • So what happens next? • Because water has a + end and a – end, it starts weakly bonding…to OTHER WATER MOLECULES!!! • Hydrogen Bonds - + + - - + + + + - - - + + + + + + http://www.saburchill.com/IBbiology/chapters01/images/11010328.jpg

26. Wait a second… • Let’s be very clear for a moment. • Between two or more water molecules, there is hydrogen bonding. • Within one water molecule, there is covalent bonding. • Please make sure this is clear to you…any questions?

27. Video Review • And now, three minutes of the best water properties review you could possibly have. • TED: Christina Kleinberg - How Polarity Makes Water Behave Strangely

28. Great, it’s polar. So…what? • Why is it important that water is polar? Because water is a polar molecule, it can dissolve or interact with other polar molecules. • This is critically important for cells to carry on life, as we will see later. • Non-polar molecules generally do not interact with water (or other polar molecules). • Hydrophilic: Water-liking, molecules that are polar. • Hydrophobic: Water-fearing, molecules that are non-polar.

29. Hydrophobic/Hydrophilic • Hydrophilic substances can dissolve easily in water. • Hydrophobic substances cannot. • Oil, for example, doesn’t. That’s why you see this: http://www.ecofriendlymag.com/wp-content/plugins/wp-o-matic/cache/9e8b0_bp-leak-gusher.jpg

30. Hydrophobic/Hydrophilic http://static.guim.co.uk/sys-images/Environment/Pix/columnists/2010/5/20/1274366784453/Deepwater-Horizon-oil-spi-006.jpg

31. Hydrophobic/Hydrophilic http://www.newsoxy.com/images/0706/tar-balls-3.jpg

32. Hydrophilic/Hydrophobic http://inapcache.boston.com/universal/site_graphics/blogs/bigpicture/oil_06_03/o01_23681845.jpg http://inapcache.boston.com/universal/site_graphics/blogs/bigpicture/oil_06_03/o02_23681001.jpg http://www.yoganonymous.com/wp-content/uploads/2010/06/save-the-sea-turtles.jpg

33. Hydrophobicity in Practice • TED: Mark Shaw – One Very Dry Demo

34. Enough notes… • …it’s time for a lab! • You will be working in groups of four at your lab tables. • Each one of you needs a computer.

35. Properties of Water Lab • Bring your lab notebooks! • You’ll want to make some notes. • Log into Quia.com/web and visit our class web page – THIS IS WHERE THE LAB IS POSTED • [firstnamelastname]832 • Gleicher[house/apt #] • Lab is called “Lab – Water”