AP BIOLOGY UNIT 1 TEST LATEST UPDATE
1. What are the key properties of water?
A. Nonpolar and hydrophobic
B. Polar molecule with polar covalent bonds and cohesive properties
C. Made only of ionic bonds
D. Cannot dissolve substances
Correct Answer: B. Polar molecule with polar covalent bonds and cohesive properties
Rationale: Water is a polar molecule because oxygen has a partial negative charge and hydrogen
atoms have partial positive charges. This polarity allows hydrogen bonding and cohesion.
Exam Tip: Water’s polarity is the reason for many of its unique biological properties.
2. What are polar covalent bonds?
A. Bonds with equal sharing of electrons
B. Bonds where electrons are completely transferred
C. Bonds where opposite ends of a molecule have opposite charges
D. Bonds formed only between metals
Correct Answer: C. Bonds where opposite ends of a molecule have opposite charges
Rationale: In polar covalent bonds, electrons are shared unequally, creating partial positive and
negative regions.
Exam Tip: Unequal electron sharing = polarity.
3. What is cohesion?
A. Water bonding to other substances
B. Attraction between water molecules caused by hydrogen bonding
C. Repelling force between ions
D. Breaking of hydrogen bonds
Correct Answer: B. Attraction between water molecules caused by hydrogen bonding
Rationale: Cohesion occurs because hydrogen bonds make water molecules “stick” together.
Exam Tip: Cohesion helps water move upward in plants during transpiration.
,4. Which property helps water move against gravity in plants?
A. Adhesion only
B. Ionic bonding
C. Cohesion
D. Diffusion
Correct Answer: C. Cohesion
Rationale: Cohesion allows water molecules to pull each other upward through plant vessels.
Exam Tip: Cohesion + transpiration = water transport in trees.
5. What is adhesion?
A. Water bonding to itself
B. Water forming hydrogen bonds with other substances
C. Water freezing into crystals
D. Water becoming hydrophobic
Correct Answer: B. Water forming hydrogen bonds with other substances
Rationale: Adhesion occurs when water molecules are attracted to other materials, enabling
capillary action.
Exam Tip: Adhesion explains why water climbs up paper towels or plant fibers.
6. Why is water considered the universal solvent?
A. It dissolves only nonpolar substances
B. It dissolves many ionic and polar substances
C. It cannot form hydrogen bonds
D. It is always neutral
Correct Answer: B. It dissolves many ionic and polar substances
Rationale: Polar water molecules surround ions and polar molecules, causing them to dissolve.
Exam Tip: “Like dissolves like” — polar solvents dissolve polar substances.
,7. What does hydrophilic mean?
A. Repelled by water
B. Dissolves only in oil
C. Having an affinity for water
D. Unable to form bonds
Correct Answer: C. Having an affinity for water
Rationale: Hydrophilic substances are usually polar or ionic and interact easily with water.
Exam Tip: “Hydro” = water, “philic” = loving.
8. Which of the following is hydrophilic?
A. Oil
B. Fat
C. Cotton
D. Glycerol
Correct Answer: C. Cotton
Rationale: Cotton is made of cellulose, which interacts well with water.
Exam Tip: Polar substances are generally hydrophilic.
9. What does hydrophobic mean?
A. Attracted to water
B. Soluble in water
C. No affinity for water
D. Positively charged
Correct Answer: C. No affinity for water
Rationale: Hydrophobic substances are usually nonpolar and do not mix with water.
Exam Tip: Oils and fats are classic hydrophobic substances.
, 10. Why does ice float on water?
A. Ice is denser than liquid water
B. Ice forms a crystal lattice structure that lowers density
C. Ice contains trapped oxygen gas
D. Ice loses hydrogen bonds
Correct Answer: B. Ice forms a crystal lattice structure that lowers density
Rationale: Hydrogen bonding creates a crystal structure in ice that spaces molecules farther
apart.
Exam Tip: Water is unusual because its solid form is less dense than its liquid form.
11. What is specific heat?
A. The amount of energy needed to boil water
B. The heat needed to change 1 g of a substance by 1°C
C. The energy stored in chemical bonds
D. The process of evaporation
Correct Answer: B. The heat needed to change 1 g of a substance by 1°C
Rationale: Water has a high specific heat because hydrogen bonds resist temperature change.
Exam Tip: High specific heat helps stabilize Earth’s climate.
12. What is evaporative cooling?
A. Cooling caused by freezing
B. Cooling caused when water evaporates from a surface
C. Cooling caused by pressure changes
D. Cooling caused by dissolving salts
Correct Answer: B. Cooling caused when water evaporates from a surface
Rationale: As water evaporates, the highest-energy molecules leave, lowering the surface
temperature.
Exam Tip: Sweating is an example of evaporative cooling.
1. What are the key properties of water?
A. Nonpolar and hydrophobic
B. Polar molecule with polar covalent bonds and cohesive properties
C. Made only of ionic bonds
D. Cannot dissolve substances
Correct Answer: B. Polar molecule with polar covalent bonds and cohesive properties
Rationale: Water is a polar molecule because oxygen has a partial negative charge and hydrogen
atoms have partial positive charges. This polarity allows hydrogen bonding and cohesion.
Exam Tip: Water’s polarity is the reason for many of its unique biological properties.
2. What are polar covalent bonds?
A. Bonds with equal sharing of electrons
B. Bonds where electrons are completely transferred
C. Bonds where opposite ends of a molecule have opposite charges
D. Bonds formed only between metals
Correct Answer: C. Bonds where opposite ends of a molecule have opposite charges
Rationale: In polar covalent bonds, electrons are shared unequally, creating partial positive and
negative regions.
Exam Tip: Unequal electron sharing = polarity.
3. What is cohesion?
A. Water bonding to other substances
B. Attraction between water molecules caused by hydrogen bonding
C. Repelling force between ions
D. Breaking of hydrogen bonds
Correct Answer: B. Attraction between water molecules caused by hydrogen bonding
Rationale: Cohesion occurs because hydrogen bonds make water molecules “stick” together.
Exam Tip: Cohesion helps water move upward in plants during transpiration.
,4. Which property helps water move against gravity in plants?
A. Adhesion only
B. Ionic bonding
C. Cohesion
D. Diffusion
Correct Answer: C. Cohesion
Rationale: Cohesion allows water molecules to pull each other upward through plant vessels.
Exam Tip: Cohesion + transpiration = water transport in trees.
5. What is adhesion?
A. Water bonding to itself
B. Water forming hydrogen bonds with other substances
C. Water freezing into crystals
D. Water becoming hydrophobic
Correct Answer: B. Water forming hydrogen bonds with other substances
Rationale: Adhesion occurs when water molecules are attracted to other materials, enabling
capillary action.
Exam Tip: Adhesion explains why water climbs up paper towels or plant fibers.
6. Why is water considered the universal solvent?
A. It dissolves only nonpolar substances
B. It dissolves many ionic and polar substances
C. It cannot form hydrogen bonds
D. It is always neutral
Correct Answer: B. It dissolves many ionic and polar substances
Rationale: Polar water molecules surround ions and polar molecules, causing them to dissolve.
Exam Tip: “Like dissolves like” — polar solvents dissolve polar substances.
,7. What does hydrophilic mean?
A. Repelled by water
B. Dissolves only in oil
C. Having an affinity for water
D. Unable to form bonds
Correct Answer: C. Having an affinity for water
Rationale: Hydrophilic substances are usually polar or ionic and interact easily with water.
Exam Tip: “Hydro” = water, “philic” = loving.
8. Which of the following is hydrophilic?
A. Oil
B. Fat
C. Cotton
D. Glycerol
Correct Answer: C. Cotton
Rationale: Cotton is made of cellulose, which interacts well with water.
Exam Tip: Polar substances are generally hydrophilic.
9. What does hydrophobic mean?
A. Attracted to water
B. Soluble in water
C. No affinity for water
D. Positively charged
Correct Answer: C. No affinity for water
Rationale: Hydrophobic substances are usually nonpolar and do not mix with water.
Exam Tip: Oils and fats are classic hydrophobic substances.
, 10. Why does ice float on water?
A. Ice is denser than liquid water
B. Ice forms a crystal lattice structure that lowers density
C. Ice contains trapped oxygen gas
D. Ice loses hydrogen bonds
Correct Answer: B. Ice forms a crystal lattice structure that lowers density
Rationale: Hydrogen bonding creates a crystal structure in ice that spaces molecules farther
apart.
Exam Tip: Water is unusual because its solid form is less dense than its liquid form.
11. What is specific heat?
A. The amount of energy needed to boil water
B. The heat needed to change 1 g of a substance by 1°C
C. The energy stored in chemical bonds
D. The process of evaporation
Correct Answer: B. The heat needed to change 1 g of a substance by 1°C
Rationale: Water has a high specific heat because hydrogen bonds resist temperature change.
Exam Tip: High specific heat helps stabilize Earth’s climate.
12. What is evaporative cooling?
A. Cooling caused by freezing
B. Cooling caused when water evaporates from a surface
C. Cooling caused by pressure changes
D. Cooling caused by dissolving salts
Correct Answer: B. Cooling caused when water evaporates from a surface
Rationale: As water evaporates, the highest-energy molecules leave, lowering the surface
temperature.
Exam Tip: Sweating is an example of evaporative cooling.
