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General Biology: Water, Carbon, and Molecular Diversity

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  • What makes water a polar molecule?

    Water is polar because oxygen has a partial negative charge and hydrogen has a partial positive charge, creating an uneven distribution of electrons.

  • How many hydrogen bonds can a single water molecule form?

    A single water molecule can form up to four hydrogen bonds with neighboring molecules.

  • Distinguish between cohesion and adhesion.

    Cohesion is the attraction between water molecules; adhesion is the attraction between water molecules and other substances.

  • What property allows water striders to walk on water?

    Surface tension, a result of cohesion among water molecules, allows water striders to walk on water.

  • Define calorie in terms of heat.

    A calorie is the amount of heat required to raise the temperature of 1 gram of water by 1°C.

  • What does it mean that water has a high specific heat?

    High specific heat means water can absorb or release a large amount of heat with little temperature change.

  • How does hydrogen bonding contribute to water's high specific heat?

    Hydrogen bonds absorb heat when they break and release heat when they form, stabilizing water's temperature.

  • Why is water's high specific heat important for life?

    It helps moderate Earth's climate and stabilizes temperatures in organisms and environments.

  • What is evaporation and heat of vaporization?

    Evaporation is the change from liquid to gas; heat of vaporization is the heat required for this change.

  • Why does ice float and why is 4°C critical?

    Ice is less dense than liquid water due to hydrogen bonding; 4°C is the temperature where water is densest.

  • Define solvent, solute, and solution.

    Solvent dissolves substances, solute is dissolved, and solution is the mixture.

  • Why is water a good solvent?

    Water's polarity allows it to surround and dissolve many solutes, especially ionic and polar molecules.

  • Define hydrophobic and hydrophilic.

    Hydrophobic substances repel water; hydrophilic substances attract and dissolve in water.

  • What is molarity?

    Molarity is the number of moles of solute per liter of solution.

  • What ions form when water dissociates?

    Water dissociates into hydronium (H3O+ or H+) and hydroxide (OH–) ions.

  • What is the pH of pure water and why?

    Pure water has a pH of 7 because the concentrations of H+ and OH– ions are equal.

  • How does the pH scale relate to ion concentration?

    The pH scale is logarithmic; each unit change represents a 10-fold change in H+ concentration.

  • What is a buffer and its role in pH?

    A buffer minimizes pH changes by accepting or donating H+ ions.

  • What was the significance of Stanley Miller's experiment?

    It showed that organic molecules could form under early Earth conditions.

  • How many valence electrons does carbon have and how many bonds can it form?

    Carbon has 4 valence electrons and can form 4 covalent bonds with other atoms.

  • What are hydrocarbons and are they hydrophobic or hydrophilic?

    Hydrocarbons are molecules of only carbon and hydrogen; they are hydrophobic.

  • Define isotope and isomer with examples.

    Isotope: atoms with different neutron numbers (e.g., Carbon-12, Carbon-14). Isomer: molecules with same formula but different structures (e.g., glucose and fructose).

  • What is a functional group?

    A functional group is a specific group of atoms that confers characteristic properties to molecules.

  • Name three functional groups and one property each.

    Hydroxyl (-OH): polar; Carboxyl (-COOH): acidic; Amino (-NH2): basic.

  • How do functional groups affect molecular function?

    Changing functional groups changes molecule shape and chemical behavior, affecting function.

  • Give an example of enantiomers with different effects.

    Enantiomers of drugs can have different pharmacological effects, such as the two forms of thalidomide.