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Quizzes > Science > Biology

Master Water Properties in AP Biology: Take the Quiz!

Test your properties of water AP Bio knowledge: surface tension, cohesion & polarity await!

Editorial: Review CompletedCreated By: James Levi PangilinanUpdated Aug 27, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
paper art style water molecules droplets showing polarity cohesion surface tension AP Bio quiz on golden yellow background

Use this AP Biology Polarity & Water Properties quiz to practice how polarity shapes water - cohesion, adhesion, surface tension, and hydrogen bonding. In a few minutes, you can spot weak areas before the exam and lock in the big ideas. Want hands-on review? Try the water lab practice , then explore the full water properties quiz .

What is the shape of a water molecule?
Bent/angular
Linear
Trigonal planar
Tetrahedral
Water has two hydrogen atoms bonded to an oxygen atom and two lone pairs on the oxygen. The electron domain geometry is tetrahedral but the molecular shape is bent/angular due to lone pair repulsion, resulting in a bond angle of around 104.5°. This angular shape creates a polar molecule with a net dipole moment. For more information see .
What type of bond holds the two hydrogen atoms and oxygen atom within a single water molecule?
Hydrogen bond
Ionic bond
Van der Waals interaction
Covalent bond
The bond between hydrogen and oxygen atoms in a water molecule is a covalent bond, where electrons are shared between atoms. Because of oxygen's higher electronegativity, this bond is polar covalent, causing partial charges on each atom. Covalent bonding differs from ionic bonding, which involves full transfer of electrons. Learn more at .
What type of bond forms between the hydrogen atom of one water molecule and the oxygen atom of another?
Covalent bond
Hydrogen bond
Peptide bond
Ionic bond
A hydrogen bond forms when the partially positive hydrogen atom of one water molecule is attracted to the partially negative oxygen of another. These weak, non-covalent interactions are critical for many of water's unique properties, like high surface tension and specific heat. Hydrogen bonds are stronger than van der Waals interactions but weaker than covalent bonds. Further details are available on .
What property describes water molecules sticking to each other?
Surface tension
Adhesion
Osmosis
Cohesion
Cohesion refers to the attraction between like molecules, such as water molecules hydrogen bonding to each other. This property contributes to water droplets forming and the movement of water in plant xylem. Surface tension is a consequence of cohesion at an interface. See for more information.
What property describes water molecules sticking to other surfaces?
Evaporation
Diffusion
Adhesion
Cohesion
Adhesion is the attraction between water molecules and different substances, such as plant cell walls. This property works in conjunction with cohesion to drive capillary action. It is observed when water climbs along the sides of a glass tube. More information can be found at .
Which property of water is primarily responsible for the ability of insects to walk on water?
High specific heat
Surface tension
High heat of vaporization
Capillary action
Surface tension arises from cohesive forces between water molecules at the air-water interface. This tension creates a 'film' that can support lightweight objects and insects. It is a direct result of hydrogen bonding within water. For more details see .
What phenomenon allows water to travel up narrow tubes against gravity?
Osmotic pressure
Capillary action
Adhesion
Cohesion
Capillary action occurs when adhesion between water and tube walls, combined with cohesion between water molecules, causes liquid to rise in narrow spaces. This process is vital for water transport in plant roots and stems. Gravity is overcome by these intermolecular forces in small diameters. Read more at .
Why is water often called the "universal solvent"?
It dissolves many substances due to its polarity
It has low surface tension
It dissolves lipids easily
It is nonpolar so dissolves gases
Water's polarity allows it to surround and interact with various charged and polar molecules, separating and dissolving them. This makes water an excellent solvent for salts, sugars, and other biomolecules. Its high dielectric constant reduces attraction between ions. For further reading visit .
Which side of a water molecule carries a partial negative charge?
None, water is neutral
Oxygen side
Both sides equally
Hydrogen side
Oxygen is more electronegative than hydrogen, pulling shared electrons closer and acquiring a partial negative charge. The hydrogen atoms consequently carry partial positive charges. This polarity is fundamental to water's solvent and cohesive properties. Learn more at .
What enables water's high specific heat capacity?
Covalent bonding
Ionic bonding
Hydrogen bonding
Metallic bonding
Hydrogen bonds between water molecules absorb and release heat slowly, resulting in a high specific heat capacity. This property stabilizes temperature in organisms and environments. It takes significant energy to break these bonds before water's temperature can rise. See for more details.
Why does ice float on liquid water?
Hydrogen bonds in ice create a lattice that is less dense
Ice has lower heat capacity
Ice is denser due to compact structure
Ice crystals trap air bubbles
As water freezes, hydrogen bonds arrange molecules into a crystalline lattice that spaces them further apart than in liquid water. This structure reduces density, causing ice to float. This anomaly is crucial for aquatic life in cold climates. More information can be found at .
How does hydrogen bonding affect water's boiling point?
Lowers it
No effect
Makes it same as methanol
Raises it significantly
Hydrogen bonds require significant energy to break, which raises water's boiling point compared to other molecules of similar size. This elevated boiling point is essential for maintaining liquid water over a wide temperature range on Earth. The strong intermolecular attractions delay vaporization. Visit for more details.
Which term describes substances that readily interact with water?
Apolar
Hydrophilic
Hydrophobic
Amphiprotic
Hydrophilic substances have polar or charged groups that form favorable interactions with water molecules, allowing them to dissolve or mix well. In contrast, hydrophobic substances lack these groups and do not interact with water. This distinction is key in biological membrane formation and protein folding. For more, see .
What is the pH of pure water at 25°C?
1
0
7
14
Pure water undergoes autoprotolysis, producing equal concentrations of H+ and OH? ions of 1 × 10?7 M each at 25°C. pH is defined as ?log[H+], giving a value of 7 under these conditions. This neutral pH is a reference point for acid - base chemistry. Read more at .
What role do buffers play in biological systems?
They accelerate reactions
They change polarity of water
They maintain pH by neutralizing acids and bases
They increase temperature
Buffers resist changes in pH by reacting with added acids or bases, maintaining a stable environment for enzymatic and metabolic processes. They typically consist of a weak acid and its conjugate base. In blood, the bicarbonate buffer system is critical for pH homeostasis. Details at .
Which of the following correctly represents the ionization constant of water (Kw) at 25°C?
1 x 10^-14
1 x 10^-3
1 x 10^-7
1 x 10^-21
The ionization constant of water (Kw) is the product of [H+] and [OH?] concentrations at equilibrium. At 25°C, Kw equals 1 × 10?14, reflecting water's slight self-ionization. This value underpins the pH scale. Learn more at .
Why does sweat cool the body?
Water's density
Water's high latent heat of vaporization
Water's high specific heat
Water's polarity
Sweat cools the body by absorbing heat from the skin during evaporation. Water's high latent heat of vaporization means it requires significant energy to transition from liquid to gas. This energy is taken from the body, producing a cooling effect. More at .
How do hydration shells form around ions in water?
Through ionic bonds
Through metallic interactions
Through covalent bonds
Through hydrogen bonds with water dipoles
Water molecules orient their partial charges around dissolved ions, forming a hydration shell stabilized by electrostatic interactions and hydrogen bonding. The oxygen face of water orients toward cations, while hydrogens face anions. These shells prevent ions from recombining and help them stay in solution. Read more at .
What is the pH of a solution with [H+] = 1 x 10^-5 M?
5
12
3
9
pH is calculated as ?log[H+], so for [H+] = 1 × 10?5 M, pH = ?log(1 × 10?5) = 5. This formula is fundamental in acid - base chemistry. Understanding pH is crucial for biochemical and physiological processes. More at .
Which process requires more energy: melting ice or vaporizing water?
Neither requires energy
Vaporizing water
Melting ice
Both require same energy
Vaporizing water requires disrupting almost all hydrogen bonds to convert liquid into gas, demanding significantly more energy (approximately 40.7 kJ/mol) than melting ice (about 6.0 kJ/mol). These energetic differences underlie water's climate moderation. Latent heat of vaporization is key for processes such as sweating. For details see .
How does adding a nonvolatile solute to water affect its freezing point?
Converts liquid to gas
Lowers freezing point
Raises freezing point
No change
The presence of a nonvolatile solute lowers the chemical potential of the liquid phase, causing freezing point depression. This colligative property depends on solute concentration, not identity. It explains why salt is used to melt ice on roads. Learn more at .
In a buffer solution of acetic acid (pKa ~4.76) and sodium acetate, what happens when acid is added?
pH drops drastically
pH rises
Buffer precipitates
pH stays constant
When acid is added to an acetic acid/sodium acetate buffer, the conjugate base (acetate) neutralizes added H+, minimizing the pH change. The buffer system shifts equilibrium according to Le Chatelier's principle. This resistance to pH change is fundamental to biological pH regulation. For more see .
What measurement directly quantifies water's surface tension?
Conductivity
Viscosity
pH
Capillary rise height
Surface tension can be measured by the height liquid rises in a capillary tube; the greater the tension, the higher the rise against gravity. This capillary rise method relates surface tension to measurable physical parameters. It is widely used in fluid dynamics studies. More information at .
How does the dielectric constant of water affect solubility of ionic compounds?
Lowers solubility
Enhances solubility by reducing electrostatic attraction
Causes precipitation
No effect
A high dielectric constant reduces the electrostatic forces between oppositely charged ions, allowing them to separate and dissolve. Water's dielectric constant (~80 at 20°C) makes it an excellent medium for dissolving salts. This property is critical for cellular ion transport. See .
How does temperature affect the ionization constant (Kw) of water?
Decreases Kw
Increases Kw
Makes water nonpolar
No change
As temperature rises, more water molecules have sufficient energy to dissociate into H+ and OH? ions, increasing Kw. This leads to lower neutral pH values at higher temperatures. Temperature dependence of Kw is essential in temperature-sensitive biological processes. More at .
Which of the following describes the behavior of water molecules in the supercritical state?
They behave as distinct gas and liquid phases
They decompose into hydrogen and oxygen
They have properties of both liquids and gases
They behave as solid crystals
Above its critical temperature and pressure, water enters a supercritical fluid state with no clear phase boundary. It exhibits liquid-like density and gas-like diffusivity, making it a unique solvent. Supercritical water is used in green chemistry and waste treatment. For details see .
Which property explains why water has the highest surface tension among common liquids?
Weak intermolecular forces
High vapor pressure
Low molecular mass
Strong hydrogen bonding network
Water's extensive hydrogen bonding network leads to strong cohesive forces at the surface. This yields the highest surface tension of common liquids. The property is crucial for phenomena like droplet formation and capillarity. Learn more at .
Why does heavy water (D2O) have a higher melting point than normal water (H2O)?
Because D2O is nonpolar
Because D2O has lower specific heat
Because deuterium forms stronger covalent bonds than hydrogen
Because deuterium is radioactive
Deuterium has a greater mass than hydrogen, which lowers the zero-point vibrational energy in D2O molecules, strengthening hydrogen bonds. This stronger bonding raises both the melting and boiling points of heavy water relative to H2O. The isotope effect is a key concept in physical chemistry. For more information see .
How does water activity (aw) affect microbial proliferation in foods?
Water activity has no impact
Lower aw increases microbial growth
Higher aw increases microbial growth
Higher aw inhibits microbial growth
Water activity measures free water available for microbial metabolism; higher aw values support faster microbial growth. Many food preservation methods aim to reduce aw to inhibit bacterial, yeast, and mold proliferation. Understanding aw is vital in food safety and shelf-life determination. Read more at .
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Study Outcomes

  1. Understand Molecular Polarity -

    Define what is polarity AP Bio and describe how uneven electron distribution in water molecules creates a dipole that drives many of water's unique behaviors.

  2. Analyze Hydrogen Bonding -

    Explain how hydrogen bonding between water molecules underpins key properties of water AP Bio, including cohesion, adhesion, and thermal regulation.

  3. Identify Cohesion and Adhesion -

    Distinguish between cohesion and adhesion forces in water and illustrate their roles in capillary action, transport in plants, and cellular processes.

  4. Explain Surface Tension -

    Interpret how surface tension arises from molecular interactions in water and discuss its ecological and physiological importance, with surface tension AP Bio examples.

  5. Apply Thermal Properties -

    Apply concepts of high specific heat and heat of vaporization to real-world scenarios, demonstrating how water's thermal stability supports living systems.

  6. Evaluate Biological Significance -

    Assess the impact of water's characteristics on ecosystem dynamics and cellular function, reinforcing core concepts of AP Biology water properties.

Cheat Sheet

  1. Molecular Polarity -

    Water's polar nature arises because oxygen's electronegativity pulls shared electrons closer, giving O a partial negative (δ−) and H atoms partial positive (δ+). Understanding what is polarity AP Bio requires you to illustrate this dipole with a Lewis or ball-and-stick model. Mnemonic: "O wears the negative coat."

  2. Hydrogen Bonding -

    Hydrogen bonds form when a δ+ hydrogen atom in one water molecule is attracted to a δ− oxygen in another, providing cohesion and high heat capacity. Each bond (~20 kJ/mol) is weaker than a covalent bond but collectively accounts for water's unique behavior in AP Biology water properties. Remember: "Hydrogen bonds hold hands."

  3. Cohesion, Adhesion & Capillary Action -

    Water's cohesion (molecule-to-molecule) and adhesion (water-to-surface) power capillary action, enabling water to rise through plant xylem. This property is central to AP Biology properties of water and underpins nutrient transport in roots and stems. Visualize: "Water climbs vessel stairs."

  4. Surface Tension -

    Surface tension arises from cohesive hydrogen bonds at the liquid - air boundary, resulting in a "skin" that supports small insects like water striders. In surface tension AP Bio questions, you might calculate tension using units (mN/m) or describe its biological implications. Think of a tight "molecular trampoline."

  5. High Specific Heat & Thermal Stability -

    With a specific heat of 4.18 J/g·°C, water buffers environmental and cellular temperature fluctuations, a vital concept in AP Biology water properties. Use q = m·c·ΔT to calculate heat changes in exercises, reinforcing how water sustains life's thermal homeostasis. Recall: "Water's thermal cushion."

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