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highschoolbio highschoolbio
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13 years ago
1. what is polar molecule? Why is water considered polar?

2. Explain hydrogen bonding. How many hydrogen bonds can a single water molecule form?

3. Distinguish between cohesion and adhesion

4. What is demonstrated when you see beads of water on a waxed car hood?

5. Which property explains the ability of a water strider to walk on water?

6. The calorie is a unit of heat. Define calorie.

7. Water has a high specific heat. What does this mean? How does water's specific heat compare to alcohol's?

8. Explain how hydrogen bonding contributes to water's high specific heat.

9.Summarize how water's high specific heat contributes to the moderation of temperature. How is this property important to life?

10. Define evaporation. What is heat of vaporization? Explain at least three effects of this property on living organisms.

11 Ice floats! So what? Consider what would happen if ponds and other bodies of water accumulated ice at the bottom. Describe why this property of water is imporant.

12. Now, explain why ice floats. Why is 4 degree Celsius the critical temperature in this story?

13. explain why water is such a fine solvent.

14. Define hydrophobic and hydrophilic.

15. 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.

16. Can you prepare 1 liter of a 0.5 molar glucose solution? Show work.

17. Define molarity

18. What two ions form when water dissociates?

19. What is the concentration of each ion in pure water at 25 degree Celsius?

20. Water has a pH of 7. pH is defined as the negative log of the hydrogen ion concentration of [H+] Can you now see how water is assigned a pH of 7?

21 To go a step further the product of H+ and OH- concentrations is a constant 10 (small -14 at the top right of the 10)    [H+} [OH-} =10 (small -14 at top right of 10)

22. Acid precipitation is increasing. Explain its sources.

22. Discuss how CO2 emissions affect marine life and ecosystems.

Please and thank you!
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Staff Member
13 years ago
One question per post please.

Quote
1. what is polar molecule? Why is water considered polar?

A polar molecule is one that has an element that is more electronegative, causing a difference in electron pull to one part of the molecule, such as water. Water is polar because it is a highly electronegative oxygen bonded to two weakly electronegative hydrogen atoms. In other words, a molecule of water is polar because of the unequal sharing of its electrons between oxygen and hydrogen in which the former has larger electronegativity than the latter, resulting in a "bent" structure.

Quote
2. Explain hydrogen bonding. How many hydrogen bonds can a single water molecule form?

A single H20 can form 3-4 hydrogen bonds with the neighboring water molecules. 2 hydrogen atoms bond with two water molecules and the single oxygen atom can bond with 1-2 water molecules.
- Master of Science in Biology
- Bachelor of Science
highschoolbio Author
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13 years ago
Ok didn't know, these are for tomorrow for me so I'm kinda in a rush. Could you help me out with the rest as well if you don't mind?
wrote...
Staff Member
13 years ago
4. What is demonstrated when you see beads of water on a waxed car hood?

Consider water - the individual molecules "stick" to each other by hydrogen bonds - this is the cohesive property of water - it holds together. Adhesion is when something sticks to something else (like adhesive tape, glue, etc). Water has an affinity, for example, with the walls of xylem tubes and this adhesion helps move water up the plant. Both adhesion and cohesion help in the transport of water in plants.
- Master of Science in Biology
- Bachelor of Science
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Staff Member
13 years ago
4. What is demonstrated when you see beads of water on a waxed car hood?

The wax sitting on the cars paint creates a barrier for the water to sit on, and since the wax is nonpolar as it is a saturated molecule the polar water molecules are capable of being held together because of the hydrogen bonding between the molecules.
- Master of Science in Biology
- Bachelor of Science
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Staff Member
13 years ago
5. Which property explains the ability of a water strider to walk on water?

I believe it's Surface Tension.
- Master of Science in Biology
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highschoolbio Author
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13 years ago
You are the man.
wrote...
Staff Member
13 years ago
You are the man.

I'll answer the rest later.
- Master of Science in Biology
- Bachelor of Science
highschoolbio Author
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13 years ago
Ok, but I will be needing them in the next 3 hours...
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Staff Member
13 years ago
6. The calorie is a unit of heat. Define calorie.

Calorie
- Master of Science in Biology
- Bachelor of Science
wrote...
Staff Member
13 years ago
7. Water has a high specific heat. What does this mean? How does water's specific heat compare to alcohol's?

Specific heat deals with the amount of energy (in joules/gram*degrees Celsius) that must be put into one gram of a substance in order to raise the temperature of the substance one degree. A high specific heat capacity would indicate that that it takes a lot of energy to raise the temperature of the substance (i.e. water). A low specific heat capacity would mean it only takes a little bit of energy to raise the temperature of the substance (i.e. aluminum).
- Master of Science in Biology
- Bachelor of Science
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Staff Member
13 years ago
8. Explain how hydrogen bonding contributes to water's high specific heat.

As I mentioned in (7), water has an extremely high specific heat capacity. This means that it takes a lot of energy to increase the temperature of water by 1 degree compared to other chemicals. This is also due to the hydrogen bondings. As hydrogen bondings are so strong, it takes a large amount of energy to break the bonds. This is important to evaporation, boiling points etc. Why do you think it takes so long to boil water? Because an extremely large amount of energy is needed to break bonds. Also, we sweat to cool ourselves down. Water on the surface of our skin can absorb up a lot of heat before evaporating.
- Master of Science in Biology
- Bachelor of Science
wrote...
Staff Member
13 years ago
9.Summarize how water's high specific heat contributes to the moderation of temperature. How is this property important to life?

Water molecules are attracted to one another by hydrogen bonds and this restricts the movement of the molecules. This means that a relatively large amount of energy is required to increase the temperature of water (i.e. it has a high specific heat capacity) and that large bodies of water are slow to change temperature i.e. lakes and oceans. Due to their high water content, the bodies of organisms are also slow to change temperature and this makes maintaining a stable body temperature easier. Moreover, water also requires a relatively high amount of energy to become a gas and this can be used as an effective means of cooling the body by sweating and panting. Conversely, a relatively large amount of energy must be transferred away from water to make it freeze, which is important for organisms with a high body water content and for those living in water.
- Master of Science in Biology
- Bachelor of Science
highschoolbio Author
wrote...
13 years ago
Thank you for helping me, Please don't work your self too hard, just do like a couple more, and I will try to manage the rest. You are the best.
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