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About This Drill
AP Biology — Unit 1 — Water Properties & Hydrogen Bonding — Drill 2 is a practice drill. It contains 5 original questions created by Brian Stewart, a Barron's test prep author with over 20 years of tutoring experience.
Practice analyzing the unique properties of water and their biological significance with this AP Biology drill. You will evaluate how hydrogen bonding produces cohesion, adhesion, high specific heat capacity, and solvent properties, and explain how these properties support life at the cellular and organismal level.
Passage
Water is the medium of life. Its unique properties arise from the polarity of the water molecule and the hydrogen bonds that form between molecules. Each water molecule has a partial negative charge on the oxygen atom and partial positive charges on the two hydrogen atoms, making it a polar molecule. This polarity allows water molecules to form hydrogen bonds with each other and with other polar or charged molecules.
Selected Properties of Water and Their Biological Significance
| Property | Cause | Biological Significance |
|---|
| Cohesion | Hydrogen bonds between water molecules | Supports water column in xylem of plants; surface tension |
| Adhesion | Hydrogen bonds between water and polar surfaces | Capillary action; water rises in narrow tubes against gravity |
| High specific heat capacity | Many hydrogen bonds must be disrupted to raise temperature | Moderates temperature in aquatic environments and in organisms |
| High heat of vaporization | Many hydrogen bonds must be broken to vaporize | Evaporative cooling in sweating and transpiration |
| Universal solvent | Polar water surrounds and dissolves polar and ionic solutes | Allows biochemical reactions; transports dissolved nutrients |
| Ice less dense than liquid water | Hydrogen bond lattice in ice spaces molecules farther apart | Ice floats; insulates liquid water beneath; prevents total freezing |
A biology class conducted two experiments. In Experiment 1, a glass capillary tube with a 0.5 mm internal diameter and a capillary tube with a 1.0 mm internal diameter were placed upright in beakers of water. Water rose higher in the narrower tube. In Experiment 2, students applied three drops of water to a waxed surface (hydrophobic) and three drops to a glass surface (hydrophilic). The drops on the waxed surface beaded up, while the drops on the glass spread out.
Questions in This Drill
- Which property of water best explains why water rises higher in the 0.5 mm capillary tube than in the 1.0 mm tube in Experiment 1?
- In Experiment 2, drops of water on the waxed (hydrophobic) surface bead up rather than spreading out. Which of the following best explains this observation?
- A freshwater lake in a temperate climate remains unfrozen beneath a layer of surface ice throughout the winter. Which property of water is most directly responsible for allowing aquatic organisms to survive in the liquid water below?
- During intense exercise, human body temperature rises. One mechanism that prevents dangerous overheating is evaporative cooling through sweating. Which property of water makes evaporative cooling particularly effective?
- A student claims that the high specific heat capacity of water is primarily responsible for the mild temperatures experienced by coastal cities compared to inland cities at the same latitude. Which of the following best evaluates this claim?