Boiling Point, Melting Point, Solubility and Biomolecules - Vocabulary Flashcards

Vocabulary flashcards covering key terms and concepts from the lecture notes.

Boiling point

The temperature at which a liquid boils; increases with stronger intermolecular forces.

Intermolecular forces

Weak attractions between molecules (Van der Waals forces, dipole–dipole interactions, hydrogen bonding, and ion–ion interactions) that influence phase changes and solubility.

Pentane

A nonpolar hydrocarbon with weak intermolecular forces; lower boiling point compared to more polar or hydrogen-bonding groups.

Butanal

Aldehyde with moderate polarity; higher boiling point than nonpolar hydrocarbons due to dipole–dipole interactions.

1‑Butanol

Alcohol capable of hydrogen bonding; higher boiling point than nonpolar analogs due to strong intermolecular hydrogen bonds.

Surface area

The extent of the outer surface of a molecule; larger surface area can increase boiling points for similar functional groups.

Polarizability

Ease with which a molecule’s electron cloud can be distorted; greater polarizability increases London dispersion forces and often boiling points.

Atomic radius

Size of an atom’s covalent radius; influences polarizability and intermolecular interactions.

Melting point

The temperature at which a solid becomes a liquid; higher when intermolecular forces are stronger and symmetry is greater.

Functional group

A specific group of atoms that determines a compound’s chemical properties and reactions.

Symmetry (molecular)

The degree to which a molecule is balanced and uniform; more symmetry can lead to tighter packing in a crystal lattice and higher melting points.

Neopentane

A highly symmetrical alkane; tends to pack well in crystals and often has a higher melting point than less symmetric isomers.

Isopentane

A less symmetric alkane isomer; typically packs less efficiently than neopentane, affecting melting point.

Solubility

The extent to which a solute dissolves in a solvent, driven by favorable interactions and packing.

Solute

The substance being dissolved in a solvent.

Solvent

The medium in which a solute dissolves.

Like dissolves like

A rule of thumb: polar solutes dissolve best in polar solvents, nonpolar solutes in nonpolar solvents.

Hydrogen bonding

A strong dipole-dipole interaction where a hydrogen atom bonded to N, O, or F interacts with a lone pair on another electronegative atom.

Ionic compound

Compound composed of ions; typically soluble in water due to ion–dipole interactions replacing ion–ion attractions.

Ion-dipole interaction

Electrostatic interaction between an ion and a polar molecule; key in dissolution of ionic compounds in water.

Dipole-dipole interaction

Attractive forces between polar molecules due to partial charges.

Ion-ion interaction

Electrostatic attractions between oppositely charged ions in a lattice or solution; overcome during melting or dissolution.

Van der Waals forces

Weak intermolecular forces including London dispersion forces and dipole-induced dipole interactions.

Hydrophilic

Affinitiy for water; polar groups capable of hydrogen bonding with water.

Hydrophobic

Repelled by water; nonpolar or weakly polar substances tend to be water-insoluble.

Soap

Amphiphilic molecule with a hydrophilic head and a hydrophobic tail, acting as a surfactant.

Nucleophile

Electron-rich species that donates electrons to an electrophile.

Electrophile

Electron-poor species that accepts electrons from a nucleophile.

π bond

A bond formed by sideways overlap of p orbitals; weaker than a σ bond and more easily broken.

σ bond

A bond formed by end-to-end overlap of orbitals; generally stronger and less easily broken than a π bond.

Heteroatom

An atom such as N, O, or a halogen in a molecule that can influence reactivity and polarity.

Acetone

A small, polar organic solvent (carbonyl compound) that is water-miscible and a hydrogen-bond acceptor.

Butane

A nonpolar hydrocarbon; soluble in organic solvents but insoluble in water.

Ethanol

A small polar alcohol; water-soluble due to its hydroxyl group and hydrogen bonding capability.

Cholesterol

A large, mostly nonpolar lipid; insoluble in water due to its extensive hydrocarbon framework.

Vitamin A (retinol)

Fat-soluble vitamin essential for vision; ~20 carbons; contains one OH group; water-insoluble.

Vitamin C (ascorbic acid)

Water-soluble vitamin with multiple oxygen-containing groups capable of hydrogen bonding; dietary source includes citrus fruits.

Fat-soluble vitamins

Vitamins soluble in fats (e.g., A, D, E, K) that are not readily dissolved in water.

Water-soluble vitamins

Vitamins soluble in water (e.g., vitamin C and many B vitamins); often excreted readily.

Biomolecules

Organic molecules essential to life, usually with several functional groups and molecular weights typically under 1000 g/mol.

Simple sugars

Monosaccharides and simple carbohydrates; building blocks of starch and cellulose.

Amino acids

Building blocks of proteins; contain amino and carboxyl functional groups that form peptide bonds.

Nucleotides

Building blocks of nucleic acids; consist of a sugar, phosphate, and a nitrogenous base.

Lipids

A diverse group of nonpolar or amphiphilic biomolecules including fats and oils; store energy and form membranes.