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Water and Molecular Bonds in General Biology

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  • What type of bond shares electrons equally between atoms?
    Nonpolar covalent bonds share electrons equally, such as in C-C or C-H bonds.
  • What makes a covalent bond polar?
    A polar covalent bond shares electrons unequally due to differences in electronegativity, e.g., O-H bonds.
  • Why is water (H2O) a polar molecule?
    Water is polar because oxygen is more electronegative than hydrogen, causing electrons to spend more time near oxygen, creating partial charges.
  • What is the molecular shape of water and its bond angle?
    Water has a bent molecular shape with a bond angle of approximately \(104.4^\circ\) due to lone pairs on oxygen.
  • How do electronegativity values relate to bond polarity?
    Greater differences in electronegativity between atoms lead to more polar bonds; for example, O (3.44) and H (2.1) form polar bonds.
  • What is a hydrogen bond?
    A hydrogen bond is a weak attraction between a partially positive hydrogen atom and a partially negative atom like oxygen or nitrogen.
  • Are electrons shared in hydrogen bonds?
    No, hydrogen bonds are noncovalent and do not involve sharing electrons.
  • What role do hydrogen bonds play in water's properties?
    Hydrogen bonds cause water's unique properties like cohesion, high specific heat, ice floating, and solvent abilities.
  • What is the difference between hydrophilic and hydrophobic molecules?
    Hydrophilic molecules are polar and interact well with water; hydrophobic molecules are nonpolar and do not dissolve in water.
  • How does water dissolve ionic compounds like salt (NaCl)?
    Water molecules surround ions, with oxygen attracting cations (Na+) and hydrogen attracting anions (Cl-), forming a hydration shell.
  • What is the significance of water's polarity for biological molecules?
    Water's polarity allows it to dissolve polar molecules and ions, facilitating biochemical reactions and transport in cells.
  • How does the shape of methane (CH4) compare to water (H2O)?
    Methane is tetrahedral and nonpolar, while water is bent and polar due to lone pairs on oxygen.
  • What is the relationship between molecular symmetry and polarity?
    Symmetrical molecules like CO2 are often nonpolar, while asymmetrical molecules like H2O are polar.
  • What is the effect of hydrogen bonding on DNA structure?
    Hydrogen bonds hold complementary base pairs together, stabilizing the DNA double helix.
  • What is the electronegativity of oxygen and hydrogen?
    Oxygen has an electronegativity of 3.44, and hydrogen has 2.1.
  • What is the difference between polar covalent and ionic bonds?
    Polar covalent bonds share electrons unequally, while ionic bonds involve complete transfer of electrons between atoms.
  • How does water's high specific heat benefit living organisms?
    Water absorbs and stores large amounts of heat with minimal temperature change, helping organisms regulate temperature.
  • Why does ice float on liquid water?
    Ice is less dense because stable hydrogen bonds form a crystal lattice that spaces molecules further apart.
  • What is the role of lone pairs on oxygen in water's shape?
    Lone pairs repel bonded hydrogen atoms, causing the bent shape and polarity of water.
  • How do polar covalent bonds contribute to partial charges in water?
    Electrons spend more time near oxygen, giving it a partial negative charge (δ-), and hydrogens partial positive charges (δ+).