Water, Aqueous Solutions, and Intermolecular Forces

Water Molecule

Composed of two hydrogen and one oxygen atom.

Dipole Moment

Unequal sharing of electrons creates partial charges.

Hydrogen Bond

Electrostatic attraction between H and O atoms.

Boiling Point

Water's high boiling point due to hydrogen bonding.

Melting Point

Water's high melting point from strong intermolecular forces.

Surface Tension

Water's resistance to external force, due to cohesion.

Hexagonal Ice

Common ice structure with low entropy and density.

Hydrophilic

Substances that easily dissolve in water.

Hydrophobic

Nonpolar substances that do not dissolve in water.

Solvation

Process of surrounding solute particles with solvent molecules.

Electrostatic Interaction

Attraction between charged or polar molecules.

Entropy Increase

Dissolving salts raises disorder in the system.

Aqueous Environment

Water-based medium where biochemical reactions occur.

Weak Acid

Substance that partially dissociates in water.

Weak Base

Substance that partially accepts protons in water.

Crystal Lattice

Ordered arrangement of ions in solid state.

Proton Donor

Substance that releases protons in a reaction.

Proton Acceptor

Substance that gains protons in a reaction.

Nonpolar Gases

Gases with no charge separation, poorly soluble in water.

Electronegativity

Tendency of an atom to attract electrons.

Solubility

Ability of a substance to dissolve in a solvent.

Molecular Interactions

Forces that affect how molecules interact in solutions.

Bulk Water

Water with high entropy and little order.

Hydrophobic Solute

Substance with low solubility in water.

Low Entropy

Thermodynamically unfavorable state in systems.

Amphipathic Lipids

Molecules with polar and nonpolar regions.

Ordered Water Molecules

Water molecules structured around nonpolar tails.

Entropy Decrease

Reduction in randomness, leading to unfavorable states.

Non-Polar Aggregation

Non-polar molecules cluster to minimize water interaction.

Hydrogen Bonds

Energetically favorable bonds formed by polar groups.

Lipid Micelles

Aggregates formed by amphipathic lipids in water.

Ligand Binding

Interaction of hydrophobic substrates with proteins.

Van der Waals Interactions

Weak forces between nearby atoms.

London Dispersion Forces

Attractive forces due to transient dipoles.

Steric Repulsion

Repulsive forces based on atomic size.

Van der Waals Contact Distance

Distance for maximal attraction between atoms.

Van der Waals Radius

Limit of atomic proximity without repulsion.

Steric Complementarity

Fit between shapes of interacting molecules.

Biological Macromolecules

Large molecules stabilized by non-covalent interactions.

Hydrophobic Effect

Spontaneous formation of non-polar aggregates.

Hydrophobic Binding Sites

Protein regions that attract hydrophobic ligands.

Drug Design

Utilizes hydrophobic effects for therapeutic compounds.

Non-Covalent Interactions

Forces not involving electron sharing.

Hydrogen bonds

Attractive forces between polar molecules' hydrogen atoms.

Ionic Interactions

Electrostatic forces between charged species or dipoles.

Hydrophobic Effect

Ordering of water around non-polar substances.

Van der Waals Interactions

Weak attractions between all atoms, regardless of polarity.

Cumulative Effect

Weak interactions significantly influence protein structure.

Ionization of Water

Water dissociates into H+ and OH- ions.

Proton Hopping

Rapid movement of protons in water via hydrogen bonds.

Electrical Conductivity of Water

Pure water conducts electricity via ion migration.

Hydronium Ion

H2O molecule that gains a proton, forming H3O+.

Osmotic Pressure

Pressure from water movement across semipermeable membranes.

Equilibrium Constant

Ratio of products to reactants at equilibrium.

Weak Acids

Substances that partially ionize in solution.

Weak Bases

Substances that accept protons in solution.

Solvent Properties of Water

Unique characteristics due to hydrogen bonding.

Macromolecular Conformations

Stable structures influenced by noncovalent interactions.

Hydrophobic Moieties

Non-polar parts of molecules that avoid water.

Dissociation of Water

Rapid reversible process producing H+ and OH-.

Semipermeable Membrane

Barrier allowing selective passage of substances.

Proton Concentration Measurement

Experimental determination of total H+ in solution.

Hydroxide Ion

An ion formed when water loses a proton.

Diffusion Rate Comparison

Proton movement faster than Na+ and K+ diffusion.

Water Molecule Structure

Two hydrogen atoms bonded to one oxygen atom.

Hydronium Ion

A water molecule with an added proton.

Ionization of Water

Process where water dissociates into H+ and OH-.

Equilibrium Constant (Keq)

Ratio of concentrations at equilibrium for a reaction.

Water Density

Mass of water per unit volume, 55.5 M.

Ion Product of Water (Kw)

Product of [H+] and [OH-] concentrations.

Kw Value

1.0 x 10^-14 M² at 25 °C.

Neutral pH

Condition where [H+] equals [OH-], pH 7.

pH Definition

Negative logarithm of hydrogen ion concentration.

pH Scale

Logarithmic scale for acidity/basicity of solutions.

pH and pOH Relationship

pH + pOH = 14 in aqueous solutions.

Concentration of Water

55.5 M derived from water's density.

Acid-Base Reaction

Chemical reaction involving proton transfer.

Electrical Conductivity of Water

Measurement used to determine Keq value.

Hydrogen Ion Concentration

[H+] in pure water is 1 x 10^-7 M.

OH- Concentration

[OH-] in pure water is 1 x 10^-7 M.

Logarithmic Nature of pH

Each pH unit change represents tenfold concentration change.

Reversible Reactions

Chemical reactions that can proceed in both directions.

Dissociation of Water

Water splits into H+ and OH- ions.

Proton Hops

Rapid movement of protons through hydrogen bonds.

Hydrogen Bonding

Attraction between water molecules facilitating proton movement.

Enzyme Functionality

Affected by pH levels, impacting biological processes.

Acidosis Symptoms

Drowsiness, nausea, and convulsions from low pH.

Diabetes Mellitus

Condition indicated by high blood glucose and acidosis.

b-Hydroxybutyric Acid

Ketone body elevated in diabetic acidosis.

Acetoacetic Acid

Another ketone body found in diabetic patients.

Plasma pH

Measure of acidity or alkalinity in blood.

Fasting

Condition leading to increased fatty acid usage.

Pepsin

Digestive enzyme active in acidic gastric juice.

Trypsin

Digestive enzyme active in neutral small intestine.

Alkaline Phosphatase

Enzyme aiding in bone mineralization, active at alkaline pH.

Enzyme Activity

Influenced by pH, affecting metabolic processes.

pKa

Measures a molecule's acidity and proton loss tendency.

Strong acids

Completely ionize in water, releasing H+.

Weak acids

Partially ionize in water, not fully dissociated.

HA

Generic formula for a weak acid.