Water

• What makes water a polar molecule?

  Water has an oxygen atom (δ⁻) and two hydrogen atoms (δ⁺), creating a dipole. This polarity allows water molecules to form hydrogen bonds.
• • How do hydrogen bonds form between water molecules?

  Hydrogen bonds form between the δ⁺ hydrogen of one water molecule and the δ⁻ oxygen of another, creating weak but significant intermolecular forces.
• • What is cohesion, and why is it important for plants?

  Cohesion is the attraction between water molecules due to hydrogen bonding. It allows water to form a continuous column in the xylem for transport.
• What is adhesion, and how does it assist in water transport?

  Adhesion is the attraction between water molecules and polar/charged surfaces. It helps water stick to xylem walls, enabling capillary action in plants.
• Why does water stabilize temperatures in organisms and environments?

  Water has a high specific heat capacity and high latent heat of vaporization due to hydrogen bonding. This allows it to absorb or release heat with minimal temperature changes.
• • Why is water called the "universal solvent"?

  Water dissolves hydrophilic substances like ions (e.g., Na⁺, Cl⁻) and polar molecules (e.g., glucose) due to its polarity, enabling transport and biochemical reactions.
• What is the difference between hydrophilic and hydrophobic substances?

  • Hydrophilic: Polar or ionic substances that dissolve in water (e.g., salts, sugars).
  • Hydrophobic: Nonpolar substances that repel water (e.g., lipids).
• Why does ice float on water?

  Ice is less dense than liquid water because hydrogen bonds form a rigid crystalline structure, increasing space between molecules.
• • How does water’s transparency benefit aquatic ecosystems?

  Transparency allows sunlight to penetrate water, supporting photosynthesis in aquatic plants and algae.
• • How does water act as a medium for life processes?

  Water dissolves reactants and products of biochemical reactions, provides a stable environment, and facilitates enzymatic activity.
• • How does water’s buoyancy support aquatic organisms?

  Water’s density reduces energy expenditure for movement and floating, enabling organisms like fish and aquatic plants to thrive.
• How do the Black-Throated Loon and Ringed Seal rely on water’s properties?

  • Black-Throated Loon: Buoyancy supports swimming; transparency allows hunting for fish.
  • Ringed Seal: Ice insulates aquatic habitats; buoyancy aids swimming and diving.
• • How do cohesion and adhesion work together in plants?

  Cohesion keeps water molecules together in a column, while adhesion helps water stick to the xylem walls, enabling capillary action for upward water transport.
• • Why is water’s high specific heat capacity important for life?

  It stabilizes temperatures in aquatic ecosystems and organisms, preventing rapid temperature changes.
• • How do hydrophobic interactions influence biological systems?

  Hydrophobic molecules (e.g., lipids) do not dissolve in water, allowing the formation of structures like cell membranes, which are essential for compartmentalization in cells.
• • What property of water enables capillary action?

  Adhesion (sticking to xylem walls) and cohesion (attraction between water molecules) together enable water to rise against gravity in narrow tubes.
• • Why is water essential for metabolic reactions?

  Water dissolves reactants like glucose and enzymes, provides a medium for reactions, and participates in hydrolysis and condensation reactions
• • What is surface tension, and how does it benefit organisms?

  Surface tension is created by cohesive forces at the water’s surface. It allows small organisms like water striders to walk on water.
• How does ice benefit organisms like the Ringed Seal?

  Ice insulates water below, preventing complete freezing, and provides a platform for resting and breeding.
• • Give an example of how water’s solvent properties are used in biology.

  Water dissolves oxygen and nutrients in blood plasma, allowing transport to cells for respiration and energy production.