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Water and Life - General Biology

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  • Why is water a polar molecule?
    Water is polar because the electrons in the polar covalent bonds spend more time near oxygen than hydrogen, creating an uneven charge distribution.
  • What allows water molecules to form hydrogen bonds?
    The polarity of water molecules allows them to form hydrogen bonds with each other.
  • What is cohesion in water?
    Cohesion is the phenomenon where hydrogen bonds hold water molecules together, resulting in high surface tension.
  • How does cohesion help plants?
    Cohesion helps transport water and dissolved nutrients against gravity in plants, aided by adhesion between water and plant cell walls.
  • How does water moderate temperature?
    Water absorbs heat from warmer air and releases heat to cooler air, changing temperature only slightly due to its high specific heat.
  • Define thermal energy and temperature.
    Thermal energy is the kinetic energy of random motion of atoms or molecules; temperature is the average kinetic energy of molecules in matter.
  • What is a calorie in terms of water?
    A calorie is the heat required to raise 1 g of water by 1°C or released when 1 g of water cools by 1°C.
  • Why does water have a high specific heat?
    Water's high specific heat is due to hydrogen bonds absorbing heat when breaking and releasing heat when forming.
  • What is evaporative cooling?
    Evaporative cooling occurs when a liquid evaporates, cooling the remaining surface as heat is absorbed to convert liquid to gas.
  • Why does ice float on liquid water?
    Ice is less dense because hydrogen bonds form a crystalline lattice that spaces molecules farther apart, making ice about 10% less dense.
  • What would happen if ice sank?
    If ice sank, bodies of water would freeze solid from the bottom up, making life impossible on Earth.
  • What is a solution, solvent, and solute?
    A solution is a homogeneous liquid mixture; the solvent dissolves the solute, which is the dissolved substance.
  • Why is water a versatile solvent?
    Water's polarity allows it to dissolve ionic compounds and polar molecules by surrounding ions or polar regions with hydration shells.
  • Define hydrophilic and hydrophobic substances.
    Hydrophilic substances have an affinity for water; hydrophobic substances do not, often due to nonpolar bonds like in oils.
  • What is molarity (M)?
    Molarity is the number of moles of solute per liter of solution.
  • Why do biologists search for water on other planets?
    Water is essential for life, so finding planets with water increases the chance of discovering life elsewhere.
  • What happens when water molecules dissociate?
    Water molecules dissociate into hydronium ions (H3O+) and hydroxide ions (OH-), affecting pH balance.
  • What is the pH scale?
    The pH scale measures acidity or basicity of a solution, defined as the negative logarithm of hydronium ion concentration.
  • What is the role of buffers in living cells?
    Buffers minimize changes in pH by reversibly combining with hydrogen or hydroxide ions, maintaining stable internal pH.
  • How does ocean acidification occur?
    CO2 from fossil fuel combustion dissolves in seawater forming carbonic acid, lowering pH and affecting marine life.