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Chapter 3: Properties of Water and Their Biological Importance

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  • Why is water a polar molecule?
    Water has polar covalent bonds where electrons spend more time near oxygen than hydrogen, creating partial charges and an uneven charge distribution.
  • What causes hydrogen bonding between water molecules?
    The polarity of water molecules allows the partial positive hydrogen atoms to be attracted to the partial negative oxygen atoms of neighboring molecules.
  • Name the four emergent properties of water important for life.
    Cohesion, moderation of temperature, expansion upon freezing, and versatility as a solvent.
  • What is cohesion in water?
    Cohesion is the attraction between water molecules due to hydrogen bonding, resulting in high surface tension.
  • How does adhesion help plants?
    Adhesion is the attraction between water and other substances, like plant cell walls, helping water move upward against gravity.
  • How does water moderate temperature?
    Water absorbs and releases large amounts of heat with little temperature change due to hydrogen bonding.
  • Define specific heat and water's specific heat value.
    Specific heat is the heat needed to raise 1 g of a substance by 1ºC; water's specific heat is 1 cal/(g·ºC).
  • Why does water have a high specific heat?
    Hydrogen bonds absorb heat when breaking and release heat when forming, stabilizing water's temperature.
  • What is evaporative cooling and its biological significance?
    Evaporative cooling occurs when the fastest molecules evaporate, cooling the surface; it helps organisms regulate temperature.
  • Why does ice float on liquid water?
    Ice is less dense because hydrogen bonds form a crystalline lattice that spaces molecules farther apart than in liquid water.
  • What would happen if ice sank?
    Bodies of water would freeze solid from the bottom up, making life impossible in many aquatic environments.
  • What is a solution, solvent, and solute?
    A solution is a homogeneous mixture; the solvent dissolves the solute, which is the substance dissolved.
  • Why is water called the 'solvent of life'?
    Water's polarity allows it to dissolve many ionic and polar substances essential for life.
  • What is a hydration shell?
    A sphere of water molecules surrounding each ion when an ionic compound dissolves in water.
  • Define hydrophilic and hydrophobic substances.
    Hydrophilic substances have an affinity for water; hydrophobic substances repel water, often nonpolar.
  • What is molarity (M)?
    Molarity is the number of moles of solute per liter of solution.
  • What is the pH scale and its range for biological fluids?
    The pH scale measures H+ concentration; biological fluids typically range from pH 6 to 8.
  • How do acids and bases affect H+ concentration?
    Acids increase H+ concentration; bases reduce H+ concentration in solutions.
  • What is a buffer and its role in cells?
    Buffers minimize pH changes by reversibly combining with H+ ions, maintaining stable internal pH.
  • What is ocean acidification?
    The process where CO2 dissolves in seawater forming carbonic acid, lowering ocean pH and affecting marine life.