The polarity of water molecules results in hydrogen bonding [3]

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1 GUIDED READING - Ch. 3 PROPERTIES OF WATER NAME: Please print out these pages and HANDWRITE the answers directly on the printouts. Typed work or answers on separate sheets of paper will not be accepted. Importantly, guided readings are NOT GROUP PROJECTS!!! You, and you alone, are to answer the questions as you read. You are not to share them with another students or work together on filling it out. Please report any dishonest behavior to your instructor to be dealt with accordingly. Get in the habit of writing legibly, neatly, and in a NORMAL, MEDIUM-SIZED FONT. AP essay readers and I will skip grading anything that cannot be easily and quickly read so start perfect your handwriting. Please SCAN documents properly and upload them to Archie. Avoid taking photographs of or uploading dark, washed out, side ways, or upside down homework. Please use the scanner in the school s media lab if one is not at your disposal and keep completed guides organized in your binder to use as study and review tools. READ FOR UNDERSTANDING and not merely to complete an assignment. Though all the answers are in your textbook, you should try to put answers in your own words, maintaining accuracy and the proper use of terminology, rather than blindly copying the textbook whenever possible. The polarity of water molecules results in hydrogen bonding [3] 1. For life, water is essential. Life began in water and evolved there for 3 billion years before spreading onto land and modern life, even terrestrial life, remains tied to water [1]. Most cells are surrounded by water and are made up of 70-95% water [1]. Water displays many emergent properties as a result of its structure and molecular interaction as a polar molecule [1]. Explain in detail, why the water molecule is considered polar? 2. What kind of bonding is responsible for the emergent properties of water and how does this type of bonding differ from covalent bonding [2] as far as the way this bond forms and its strength? 3. Why is it unlikely that two neighboring water molecules would be arranged like the picture below [1]?

2 4. Study the water molecules to the right. [3] a. On the central molecule, label the Oxygen (O) and the Hydrogen (H). b. Add partial positive (! + ) and partial negative (! + ) signs to indicate the charged regions of each molecule. c. Indicate the hydrogen bonds. d. How many hydrogen bonds could a single water molecule form? Four emergent properties of water contribute to Earth s fitness for life. Hydrogen bonding accounts for the unique properties of water. [3] 5. What are the four emergent properties of water? Complete the following quote from your textbook reading: Water moderates air temperature by from air that is warmer and the to air that is cooler. Water is effective as a heat bank because it can or a relatively large amount of with only a slight change in its own [1] 7. For each of the below listed properties of water, 1. define the property and 2. explain how water s polar nature AND its intermolecular bonding contributes to this special property. Lastly, also 3. describe an example in nature illustrating each property [2]. a. Cohesion

3 b. Adhesion c. Surface tension d. High specific heat

4 e. Heat of vaporization f. Evaporative cooling 8. Let s see if you got the concepts down. What causes beads of water to form on a waxed car hood? [3] 9. What allows a water strider to walk on water? [3] 10. The calorie is a unit of heat. Define calorie. [3] 11. How does water s specific heat compare to alcohol s? [3] Why is this the case?

5 12. Summarize how water s specific heat contributes to the moderation of temperature. How is this property important to life? [3] 13. Define evaporation. 14. What is special about water and its density [2] compared to other substances and why does this phenomenon occur (be sure to mention by 4 C is such a critical temperature in this story)? 15. Why is the fact that ice floats so important to life? 16. Briefly define the following terms [2]: a. Solution

6 b. Solute c. Solvent d. Aqueous solution e. Hydration Shell f. Hydrophilic g. Colloid h. Hydrophobic i. Molecular Mass j. Mole (mol) k. Molarity 17. Consider coffee in which you have added sugar. Which is the solvent and which is the solute? [3]

7 18. Why is water such a fine solvent? 19. You already know that some materials, such as olive oil, will not dissolve in water. In fact, oil will float on top of water. Explain this property in terms of hydrogen bonding. [3] 20. Now, let s do a little work that will enable you to prepare solutions. Read the section on solute concentrations carefully, and show the calculations here for preparing a 1-molar solution of sucrose. Steps to help you do this follow. The first step is done for you. Fill in the rest. [3] Steps to prepare a solution: a. Write the molecular formula for sucrose. C 12 H 22 O 11 b. Use your periodic table to calculate the mass of each element. Multiply by the number of atoms of the element. (Ex: O has a mass of 16 g/mol. Therefore one mole of O has a mass of 16 x 11 = 176 g/mole.) c. Add the masses of each element in the molecule. This is the mass of one mole of this molecule. d. Add this mass of the compound to water to bring it to a volume of 1 liter. This makes 1 liter of a 1-M (1 molar) solution. 21. Can you prepare 1 liter of a 0.5-molar glucose solution? Show your work.

8 Acid and basic conditions affect living organisms. [3] 22. a. Label the diagram below to demonstrate the dissociation of the water molecule [2]. b. What is the concentration of each ion in pure water at 25 C. [3] 23. What defines an acid and a base (be sure to include an explanation of both the direct and indirect ways different types bases work)? 24. a. Provide the formula to calculate ph? b. Water is neutral has a ph of 7. The product of H+ and OH- concentrations is a constant. What is this constant? c. What is the ph of 0.05 M HCl considering HCl is a strong acid, dissociating completely in water? Show work. 25. Because the ph scale is logarithmic, each numerical change represents a 10x change in hydrogen ion concentration. [3] a. Does a solution with a ph of 9 have a higher or lower concentration of ions compared to a ph of 2? b. Consider two solutions of equal volume. Compared to the acidic solution at ph 2, the basic solution at ph 8 has times as many hydrogen ions [1]. c. Explain the difference between a ph of 8 and a ph of 12 in terms of H + concentration. 26. If hydrogen ions are removed from a solution, will its ph drop or rise?

9 27. In your own words, describe why apparently small changes in ph are so important in biology [2]? 28. a. Even a slight change in ph can be harmful! What is a buffer and how does it work exactly? In addition to text, include a graph that shows the buffering range for a generic buffer with properly labeled x- and y-axes. A graph alone without text will not do in an AP science course. b. Write out and explain the carbonic acid buffer system in human blood [2]. " 29. What is acid precipitation, why does it occur, and why is it of importance to living organisms [2]?

10 30. Explain two reasons why it matters to biology if CO 2 levels rise? 31. Please answer the Self-Quiz at the end of your chapter. Do your best to try it from memory first in order to test how well you grasped the material and so you see what you need to spend more time on References 1. Campbell et al. (2008). AP* Edition Biology. 8 th Ed. San Francisco: Pearson Benjamin Cummings. 2. Adapted from L. Miriello 3. Adapted from Fred and Theresa Holtzclaw