Honors Biology

1. Honors Biology • WATER AND pH Notes

2. Characteristics of Water • http://www.allaboutwater.org/water-facts.html Cool water facts. • A single water molecule is held together by polar covalent bonds, BUT, if you want to attach a bunch of water molecules together, (Which is normally what we think of when we hear the word water), we need Hydrogen Bonds.

3. Molecule Image • Dotted lines are the Hydrogen Bonds

4. Key Properties of Water (table 3.2) • A) Heat storage • B) Ice Formation • C) High Heat of Vaporization • D) Cohesion/adhesion • E) Hydrophobic/hydrophilic

5. Heat Storage • When talking about temperature, we are really talking about how fast molecules are moving. IF they move fast, the temperature is high, if they move slowly, the temperature is low. • Large input of thermal energy is required to disrupt the organization of liquid water • This minimizes temperature changes • Water heats up and cools down VERY slowly because you first need to break the hydrogen bonds.

6. Biological importance of heat storage • Your body doesn’t immediately boil when you step outside in July. • You can swim in your swimming pools in October and not freeze, but you can’t jump in your pool during June before the pool heats up enough. • What other things can you think of?

7. B) Ice Formation • Low temperature means the H-Bonds are pretty stable, but they may take on a cool property. They arrange themselves in a way that makes ice LESS dense as a solid. Most other liquids react the opposite when they get colder.

8. Biological Importance of Ice Formation • Ice floats! • Oceans/bodies of water freeze from the top down. Creates a nice insulated layer so that life can still exist in the ocean. • Any other reasons you can think of?

10. C) High heat of vaporization • To Vaporize means to turn into a gas. What does it take for liquid water to do this? • Move fast enough so that the H-bonds can break. When the H-Bond is broken, it carries with it a great deal of heat!

11. Biological importance ….. • Sweating cools you off! When you sweat, the fast moving water is literally leaving your body… the molecules left behind are moving slowly so you feel cooler.

12. D) Cohesion/Adhesion • Because of the H-Bonds, water can stick to other water molecules and to other objects. (Examples: Capillary Action and Surface Tension)

13. Biological Importance of Cohesion/Adhesion • http://www.youtube.com/watch?v=CT4pURpXkbY • Towels can actually dry you off when you get out of the shower. • Straws work • Any other ideas?

14. Surface tension • Molecules inside a water droplet are attracted in all directions. Drops on the surface are attracted to the sides and inward.

15. Cohesion VS Adhesion • The mutual attractive force that exists between like molecules of a particular liquid is called cohesion. This force is responsible for holding a raindrop together as a single unit. Cohesion produces the phenomenon known as surface tension, which may allow objects that are more dense than the liquid to be supported on the surface of the liquid without sinking. When an attractive force exists between two unlike materials, such as a liquid and a solid container, the attractive force is known as adhesion. Adhesion is the force that causes water to stick to the inside of a glass

16. Capillary Action • Capillary action, or capillarity, is the ability of a liquid to flow against gravity where liquid spontaneously rises in a narrow space such as a thin tube, or in porous materials such as paper or in some non-porous materials such as liquified carbon fibre. This effect can cause liquids to flow against the force of gravity or the magnetic field induction.

17. E) Hydrophobic and Hydrophilic • The term Hydrophobic means “water fearing”. • The term Hydrophilic means “water loving”. • The terms really mean the ability or inability to DISSOLVE in water. Like dissolves like. • Since water is polar, any polar molecule can dissolve in water.

18. Biologic Importance • Most of our blood is made up of water, so nutrients can be dissolved in our blood and transported through out the body without needing to be big and clunky and blocking up the veins and arteries. • Our skin must be hydrophobic since we don’t dissolve when it rains.

19. Structure of Water video • http://www.youtube.com/watch?v=KiZJOTt3Dl0&feature=related

20. pH • Reminder: Water is held together by ___________________ bonds. • These are relatively __________ bonds. • These bonds are constantly _________ and _____________. • When water breaks apart, there is a way to represent this using chemical equations. (Dissociation of water)

21. Dissociation of water • IF you measure how much is H= you would find the concentration to be 1/10,000,000. • Use exponents 10 ^ -7 • [ ] brackets mean “concentration” so [H+] is translated to concentration of Hydrogen

22. [H+] and pH values are opposite! • A) if pH is low, what about the [H+] ? • B) if the pH is high, what about the [H+]?

23. Acids vs Bases • Acids: Anything that dissolves in water and adds H+. OH NO! IMBALANCE! • Bases: Anything that dissolves in water and combines with H+. Not necessarily bad, but now there is an imbalance with the OH- ion. • THEY NEED TO STAY BALANCED!

24. BUFFERS • What would a buffer do if pH falls? • What would a buffer do if pH rises?