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AP Biology Quiz Prep Unit 1
Biology (Wayzata High School)
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AP Biology Quiz Prep: Unit 1.1 — Water &
Chemical Bonds
Part I — AP-Style Multiple Choice
1. Hydrogen bonding
Water molecules are able to form hydrogen bonds primarily because
A. electrons are transferred from hydrogen to oxygen.
B. oxygen attracts shared electrons more strongly than hydrogen.
C. hydrogen and oxygen share electrons equally.
D. water molecules contain ionic bonds.
Answer: B
Why: The O–H bonds are polar covalent. Oxygen's greater electronegativity creates partial
charges that allow hydrogen bonding between water molecules.
2. Covalent vs. hydrogen bonds
Which statement correctly compares the bonds within and between water molecules?
A. Hydrogen bonds occur within water molecules, and covalent bonds occur between them.
B. Ionic bonds occur within water molecules, and hydrogen bonds occur between them.
C. Polar covalent bonds occur within water molecules, and hydrogen bonds occur between
them.
D. Nonpolar covalent bonds occur within water molecules, and ionic bonds occur between
them.
Answer: C
3. Polarity
Which characteristic of a water molecule causes it to be polar?
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A. Water contains two hydrogen atoms.
B. Oxygen and hydrogen share electrons unequally.
C. Water forms covalent bonds with neighboring molecules.
D. Oxygen transfers electrons completely to hydrogen.
Answer: B
4. Nonpolar molecule
A molecule consisting primarily of carbon and hydrogen has electrons distributed relatively
evenly throughout the molecule.
The molecule is most likely
A. polar and hydrophilic.
B. nonpolar and hydrophobic.
C. ionic and hydrophilic.
D. charged and soluble in water.
Answer: B
Now make it biological
5. High specific heat
A lake experiences relatively small changes in water temperature even though the surrounding
air temperature changes substantially between day and night.
Which property of water best explains this observation?
A. Low density of ice
B. High specific heat capacity
C. Adhesion
D. High surface tension
Answer: B
6. WHY does high specific heat matter?
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Water's high specific heat helps organisms maintain relatively stable body temperatures
because
A. water rapidly releases all absorbed heat.
B. large amounts of energy are required to disrupt hydrogen bonds before water temperature
rises substantially.
C. covalent bonds within water molecules frequently break.
D. water molecules become nonpolar when heated.
Answer: B
Hydrogen bonds → energy requirement → temperature stability → biology
7. Biological relevance
Which organism would benefit most directly from water's high specific heat?
A. A bacterium using glucose during respiration
B. A fish living in a lake with changing air temperatures
C. A plant absorbing nitrate ions
D. A fungus releasing digestive enzymes
Answer: B
Evaporative cooling
8.
A runner's body temperature decreases as sweat evaporates from the skin.
Which property of water most directly explains this effect?
A. Water has a high heat of vaporization.
B. Solid water is less dense than liquid water.
C. Water adheres to polar surfaces.
D. Water dissociates into ions.
Answer: A
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9. Harder
Why does evaporation of sweat cool the body?
A. The coolest water molecules leave the skin first.
B. High-energy water molecules escape into the air, carrying thermal energy with them.
C. Hydrogen bonds within individual water molecules break.
D. Water molecules release heat when they become gas.
Answer: B
10. Plant application
During a hot day, water evaporates from leaves through stomata.
In addition to contributing to water movement through the plant, this process can
A. increase leaf temperature.
B. provide evaporative cooling.
C. prevent hydrogen bonding.
D. decrease water polarity.
Answer: B
Cohesion, Adhesion & Capillary Action
11.
Water molecules moving upward through xylem tend to remain connected to one another
primarily because of
A. adhesion.
B. cohesion.
C. ionic bonding.
D. hydrophobic interactions.
Answer: B
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12.
Water molecules interact with the polar walls of xylem vessels.
This interaction is an example of
A. cohesion.
B. adhesion.
C. surface tension.
D. nonpolar bonding.
Answer: B
13. AP reasoning
Water can move considerable distances upward through narrow plant xylem vessels despite
gravity.
Which combination of properties contributes most directly?
A. Cohesion and adhesion
B. High specific heat and low ice density
C. Hydrophobicity and ionic bonding
D. High pH and low surface tension
Answer: A
14.
A student places a thin glass tube into a container of water. Water rises several centimeters
inside the tube.
Which explanation best accounts for this observation?
A. Water molecules repel one another.
B. Adhesion attracts water to the glass while cohesion pulls additional water molecules upward.
C. Covalent bonds between water molecules cause them to climb the tube.
D. Water becomes less dense inside narrow tubes.
Answer: B
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Surface Tension
15.
A water strider can remain on the surface of a pond without immediately sinking.
Which property contributes most directly?
A. High specific heat
B. Surface tension resulting from cohesion
C. Adhesion to nonpolar substances
D. Low heat of vaporization
Answer: B
16. Experimental reasoning
A researcher adds a detergent that disrupts hydrogen bonding among surface water molecules.
What would most likely happen?
A. Surface tension would increase.
B. Surface tension would decrease.
C. Water would become ionic.
D. Water's covalent bonds would disappear.
Answer: B
Ice Floating
17.
Why is solid water less dense than liquid water?
A. Water molecules lose mass when freezing.
B. Hydrogen bonds arrange water molecules into an open crystalline structure.
C. Covalent bonds between hydrogen and oxygen disappear.
D. Oxygen atoms move closer together during freezing.
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Answer: B
18. Biological significance
What is an important biological consequence of ice being less dense than liquid water?
A. Lakes freeze from the bottom upward.
B. Ice sinks and provides nutrients to aquatic organisms.
C. Surface ice can insulate liquid water below, allowing aquatic organisms to survive winter
conditions.
D. Frozen water has greater ability to dissolve ions.
Answer: C
19. Excellent AP-style “what if?”
Suppose solid water were more dense than liquid water.
Which consequence would be most likely in a cold freshwater lake?
A. Ice would remain at the surface and increase insulation.
B. Ice would sink, potentially allowing much more of the lake to freeze.
C. Surface tension would dramatically increase.
D. Water would become nonpolar at low temperatures.
Answer: B
Water as a Solvent
20.
Sodium chloride dissolves readily in water primarily because
A. water forms covalent bonds with sodium and chloride.
B. the partial charges of water molecules interact with the charged ions.
C. sodium chloride becomes nonpolar in water.
D. hydrogen atoms remove electrons from chloride.
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Answer: B
21.
Which substance would most likely dissolve readily in water?
A. A nonpolar hydrocarbon
B. An ionic compound
C. A long chain composed only of carbon and hydrogen
D. A neutral lipid
Answer: B
22. Biological application
Water's ability to dissolve many ionic and polar compounds is particularly important to cells
because it
A. allows many biochemical reactions to occur in an aqueous environment.
B. prevents ions from interacting with proteins.
C. eliminates the need for cellular membranes.
D. makes all biological molecules soluble.
Answer: A
Notice the important word many, not all.
23.
Why are lipids such as oils generally insoluble in water?
A. Lipids contain ionic bonds that repel water.
B. Most lipids are largely nonpolar and cannot form favorable interactions with polar water
molecules.
C. Water molecules are too large to interact with lipids.
D. Lipids contain stronger hydrogen bonds than water.
Answer: B
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pH
24.
A solution changes from pH 7 to pH 5.
The hydrogen ion concentration has
A. increased 2 times.
B. increased 10 times.
C. increased 100 times.
D. decreased 100 times.
Answer: C
25.
Solution A has a pH of 3, and solution B has a pH of 6.
Compared with solution B, solution A has approximately
A. 3 times more H⁺.
B. 30 times more H⁺.
C. 100 times more H⁺.
D. 1,000 times more H⁺.
Answer: D
26.
A solution with a pH of 9 is best described as
A. acidic, with relatively high H⁺ concentration.
B. basic, with relatively low H⁺ concentration.
C. neutral, because its pH is close to 7.
D. acidic, because it contains OH⁻.
Answer: B
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Integrating Scientific Inquiry
Now I would mix in the scientific reasoning you've been teaching.
27.
A student hypothesizes that increasing salt concentration decreases the rate of seed
germination.
Which statement is the best prediction?
A. Salt affects seed germination because water movement is important to cells.
B. Seeds exposed to higher salt concentrations will have lower germination percentages.
C. Seeds exposed to 2% salt had a 45% germination rate.
D. Increasing salt decreased germination.
Answer: B
28.
The student obtains these results:
NaCl
Germination
0%
92%
1%
73%
2%
48%
3%
21%
Which is the best claim?
A. Salt influences osmosis.
B. Increasing NaCl concentration was associated with decreased seed germination under the
conditions tested.
C. At 3% NaCl, germination was 21%.
D. Seeds require water.
Answer: B
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29.
Which is the strongest evidence for that claim?
A. Seeds require water for germination.
B. Germination decreased from 92% at 0% NaCl to 21% at 3% NaCl.
C. Salt can dissolve in water.
D. The student predicted that germination would decrease.
Answer: B
30.
Which statement provides the strongest reasoning?
A. Germination was lower when salt concentration was higher.
B. High external solute concentration can reduce water movement into seed cells, limiting
processes required for germination.
C. The highest concentration was 3%.
D. The seeds were placed in salt solutions.
Answer: B
Beautiful CER distinction:
Claim: Salt decreased germination.
Evidence: 92% → 21%.
Reasoning: Water potential/osmosis explains why.
A Short AP-Style FRQ
I would finish their review with this.
A researcher investigates whether humidity affects water loss from plant leaves. Identical plants
are placed under either 30% humidity or 80% humidity for one hour.
The plants at 30% humidity lose an average of 4.8 g of water, while plants at 80% humidity lose
an average of 1.7 g.
A.
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Identify the independent variable.
Humidity
B.
Identify the dependent variable.
Amount/rate of water loss
C.
Write an appropriate null hypothesis.
Humidity has no effect on water loss from the plants.
D.
Write an appropriate alternative hypothesis.
Humidity affects water loss from the plants.
E.
Make a claim supported by the results.
Plants exposed to lower humidity lost more water.
F.
Provide evidence.
Plants at 30% humidity lost 4.8 g compared with 1.7 g at 80% humidity.
G.
Explain the result using a property of water.
A good response:
Water molecules cohere through hydrogen bonding. During transpiration,
evaporation from leaves helps pull the continuous column of water through the
xylem. Lower atmospheric humidity creates conditions that favor greater
evaporation from the leaf, increasing water loss.
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