AP Biology Reading Guide
Fred and Theresa Holtzclaw
Chapter 3: Water and the Fitness of the Environment
G
Name_______________________Period___________
Daniela
Chapter 3: Water and the Fitness of the Environment
Concept 3.1 The polarity of water molecules results in
hydrogen bonding
1. Study the water molecules at the right. On the central
molecule, label oxygen (O) and hydrogen (H).
2. What is a polar molecule? Why is water considered polar?
OI
Ht Ht
A polar molecule is
a molecule that has
a positive and
negative charge.
Attracts other molecules because
water attracts hydrogen bonds
because it has positive and
negative bonds.
oÉo
Ht
3. Now, add + and – signs to indicate the charged regions of
each molecule. Then, indicate the hydrogen bonds.
4. Explain hydrogen bonding. How many hydrogen bonds can
a single water molecule form?
Water can form two
hydrogen bonds.
Adhesion
is
an attractionbetween
different substances
Concept 3.2 Four emergent properties of water contribute to Earth’s fitness for life
Hydrogen bonding accounts for the unique properties of water. Let’s look at several.
Motion
Cohesion
5. Distinguish between cohesion and adhesion.
Cohesion helps the transport of water against gravity in plants. Adhesion is an
attraction between di erent substances for example
6. What is demonstrated when you see beads of water on a waxed car hood?
1kcal 1,000cal
239or 4.18
11
units
calories
Adhesion
are
energy
7. Which property explains the ability of a water strider to walk on water?
Surface tension
Moderation of Temperature
8. The calorie is a unit of heat. Define calorie.
Calorie is a unit of energy of thermal
energy.
9. Water has high specific heat. What does this mean? How does water’s specific heat compare to
alcohol’s? Speci c heat of water 1cal|g|°c
Water evaporates slower to alcohol due to
its high speci c heat.
10. Explain how hydrogen bonding contributes to water’s high specific heat.
Heat forms when those hydrogen bonds break so since there’s
a lot of bonds it causes it to have higher speci c heat.
Copyright © 2010 Pearson Education, Inc.
-1-
AP Biology Reading Guide
Fred and Theresa Holtzclaw
Chapter 3: Water and the Fitness of the Environment
11. Summarize how water’s high specific heat contributes to the moderation of temperature. How is this
property important to life?
Watershigh specific heat traces to hydrogenbonding
it's important cause high specific heat of water minimizes temp fluctuations to within
Permit
limits thatWhat
12. Define evaporation.
is heatlife
of vaporization? Explain at least three effects of this property on
living organisms.
Evaporation is when liquid
transforms into gas but heat of
vaporization is the heat a liquid
must absorb for 1 g to be
converted to gas.
Expansion upon Freezing
Three a ects
1-Evaporative cooling of water helps stabilize
temp in organisms and bodies of water.
2- Evaporations can lead to droughts causing
organisms to die.
3-When evaporation occurs it results in
participation causing it to rain living plants water.
13. 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 important.
They would ow up because ice is less dense than
water. This is because of the hydrogen bonds in
ice are more “ordered”.
14. Now, explain why ice floats. Why is 4oC the critical temperature in this story?
When water reaches its greatest density its at 4
Celsius.
Solvent of Life
15. Review and define these terms:
solvent A substance that dissolves in a solute to make a
mixture.
solution
solute
Is the result of a solute and solvent mixture.
The substance that disolves IN a solvent.
16. Consider coffee to which you have added sugar. Which is the solvent? The solute?
Sugar- solute
Co ee- solvent
17. Explain why water is such a fine solvent.
Water is a versatile solvent due to its polarity
18. Define hydrophobic and hydrophilic.
Hydrophilic attracts water
Hydrophobic pushes away water
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.
This is because olive oil is less dense that water
and its also hydrophobic to water.
Copyright © 2010 Pearson Education, Inc.
-2-
AP Biology Reading Guide
Fred and Theresa Holtzclaw
Chapter 3: Water and the Fitness of the Environment
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.
Steps to prepare a solution:
a.
Write the molecular formula.
C12H22O11
b.
Use your periodic table to calculate the mass of each element. Multiply by the number of atoms of
the element. (For example, O has a mass of 16. 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.
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 here.
NIA
don't
have mativiels
wasn't taught
22. Define molarity.
Number of moles of solute per liter of solution.
Concept 3.3 Acidic and basic conditions affect living organisms
23. What two ions form when water dissociates?
Hydronium ion and hydroxide ion
You should have answered “hydronium (H3O+) and hydroxide ions (OH–)” in the preceding question.
However, by convention, we will represent the hydronium ion as H+.
24. What is the concentration of each ion in pure water at 25oC?
H+ and OH- ——> [H+][OH-]=10-
25. Water has a pH of 7. pH is defined as the negative log of the hydrogen ion concentration [H+]. Can you
now see how water is assigned a pH of 7?
Yes
26. To go a step further, the product of H+ and OH– concentrations is constant at 10–14.
[H+}[OH–} = 10–14.
Copyright © 2010 Pearson Education, Inc.
ok
-3-
AP Biology Reading Guide
Fred and Theresa Holtzclaw
Chapter 3: Water and the Fitness of the Environment
Water, which is neutral with a pH of 7, has an equal number of H+ and OH– ions. Now, define
acid is any substance that increases the H+ acidic pit a
concentration of a solution
is any substance that reduces the H+
concentration of a solution
base
base
PHP
27. Because the pH scale is logarithmic, each numerical change represents a 10X change in ion
concentration.
a.
So, how many times more acidic is a pH of 3 compared to a pH of 5?
b.
How many times more basic is a pH of 12 compared to a pH of 8?
c.
Explain difference between a pH of 8 and a pH of 12 in terms of H+ concentration.
1Acidic
gait
2
3
40times
moreacidic
28.
On the pH chart, label pH 1–14. Label neutral, acid, base. Indicate
the locations of pure water, urine, gastric juice, and bleach.
7 Neutral
29.
Even a slight change in pH can be harmful! How do buffers moderate
pH change?
changes in concentrations
They minimize
of Ht Olt in a solution
8
9
10
bleach
40 in change
4
5
urine 6
water
20 in change
30.
12
13
14
Exercise will result in the production of CO2, which will acidify the
blood. Explain the buffering system that minimizes blood pH
changes.
Bu ering helps to keep the acidity minimized
base
because it contains weak acid and its
corresponding base which combine reversible
with H+ ions.
31. Acid precipitation is increasing. Explain its sources.
It’s coming from the environments addition of H+
ions.
32. Discuss how CO2 emissions affect marine life and ecosystems.
It causes an imbalance in the water causing ocean
acidi cation. This could be caused by burning
fossil fuels.
Testing Your Knowledge: Self-Quiz Answers
Now you should be ready to test your knowledge. Place your answers here:
NO Quiz
1._______ 2._______ 3._______ 4._______ 5._______ 6._______ 7._______ 8._______
0
Copyright © 2010 Pearson Education, Inc.
in
Pdx
-4-