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  1. Bond Classifications

    • Intramolecular Bonds: Interactions occurring within a single molecule (e.g., covalent and ionic bonds).

    • Intermolecular Bonds: Interactions occurring between separate neighboring molecules (e.g., hydrogen bonds, hydrophobic interactions, Van der Waals forces).

2. Structure and Properties of Water

  1. Polarity of Water

    • One oxygen atom covalently bonded to two hydrogen atoms

    • Partial negative charge on oxygen and a partial positive charge on each hydrogen.

  2. Hydrogen Bonding

    • An intermolecular attraction between the partial positive hydrogen of one water molecule and the partial negative oxygen of a neighboring molecule.

    • Individually weak, but strong in large numbers.

    • Represented graphically using dashed lines.

3. Physical Properties of Water

  1. Specific Heat

    • Definition: The amount of heat energy required to raise or lower the temperature of a substance by 1extC1^ ext{C}.

    • Water has a high specific heat due to its extensive network of hydrogen bonds, which provides stability

  2. Kinetic Energy and States of Matter

    • Temperature measures average kinetic energy (motion of molecules).

    • Solid (Ice): Low kinetic energy leads to stable, long-lasting hydrogen bonds. Molecules form a lattice structure with increased space between them, resulting in lower density than liquid water

    • Liquid: Moderate kinetic energy causes hydrogen bonds to continuously break and reform

    • Gas (Water Vapor): High kinetic energy causes rapid molecular movement and rapid breakage of hydrogen bonds.

  3. Cohesion and Adhesion

    • Cohesion: Hydrogen bonding between water molecules.

    • Adhesion: Hydrogen bonding between a water molecule and a different polar or charged substance

    • Together, cohesion and adhesion allow water to move upward against gravity in plants.

4. Solutions and Molecular Interactions

  1. Solution Terminology

    • Solute: The substance being dissolved.

    • Solvent: The liquid dissolving the solute (water is the primary biological solvent).

    • Solution: The homogeneous mixture formed by a solute and solvent.

  2. Dissolution and Hydration Shells

    • Polar substances and ionic salts dissolve in water due to partial or full electrical charges.

    • Anions interact with partial positive hydrogens; cations interact with partial negative oxygens.

    • Hydration Shell: A surrounding sphere of water molecules formed around dissolved ions.

  3. Water Affinity

    • Hydrophilic: "Water-loving"; polar or charged molecules that interact readily with water.

    • Hydrophobic: "Water-fearing"; nonpolar molecules that avoid interaction with water.

    • Amphipathic Molecules: Contain both hydrophilic and hydrophobic regions (e.g., phospholipids).

    • Micelle: A spherical structure formed when amphipathic molecules are placed in water, orienting hydrophilic heads outward and hydrophobic tails inward.

5. Chemical Reactions and Dynamics

  1. Reaction Terminology

    • Reactants: Starting substances in a reaction.

    • Products: End substances formed by a reaction.

    • Chemical Equilibrium: A state where forward and reverse reaction rates are equal, indicated by a double-headed arrow.

  2. Ionization of Water

    • Pure water dissociates into hydronium ions (H3O+H_3O^+) and hydroxide ions (OH−OH^-).

    • Protons are used interchangeably with hydrogen ions (H+H^+).

6. pH and Buffers

  1. The pH Scale

    • Measures the concentration of free hydrogen ions (H+H^+) on a logarithmic scale.

    • Neutral: =7.0=7.0 (equal concentrations of H+H^+ and OH−OH^-).

    • Acidic: <7.0<7.0 ; higher H+H^+ concentration.

    • Basic / Alkaline: >7.0>7.0 ; lower H+H^+ concentration.

    • Every unit change on the pH scale represents a 10imes10 imes change in H+H^+ concentration.

  2. Buffers

    • Consist of an acid-base pair that minimizes fluctuations in pH.

    • Function to stabilize system pH and maintain homeostasis within biological limits.

  • 60-70 Percent of body weight is water

  • Concentration: amount of solute dissolved in a unit of volume solution

  • Molecular mass: sum of atoms masses in a molecule

  • Molarity: number of moles dissolved in a 1 L solution of water

  • Heat Capacity: amount of heat to raise temp of the entire sample (high for water)

  • Surface tension : attraction of the molecules at surface (strong in water)

  • Changes in state involve an input or release of energy

  • Each number on the pH scale has a 10n difference