Chapter 3 - Intermolecular Forces

Intermolecular Forces

Forces of attraction between molecules.

Intramolecular Force

Within a molecule, holds atoms together.

Ionic Bonds

Bonds formed by the electrostatic attraction between oppositely charged ions.

Covalent Bonds

Bonds formed by the sharing of electrons between atoms.

Non-polar covalent

Electrons are equally shared between atoms.

Polar covalent

Electrons are unequally shared between atoms.

Dipole-Dipole Forces (DDF)

Attractive forces between polar molecules due to positive and negative dipoles.

Hydrogen Bonding (H-bond)

A stronger type of dipole-dipole interaction involving H bonded to N, O, or F.

London Dispersion Forces (LDF)

Weak attractive forces present in all molecules due to temporary dipoles.

Polarity

A molecule's property that determines how it interacts with other substances.

Hydrogen chloride

Chemical compound with the formula HCl; a polar molecule.

Gecko feet

Utilize a large amount of London dispersion forces for adhesion.

Density of water

Solid form of water is less dense than its liquid form due to hydrogen bonding.

Solubility

Ability of a substance to dissolve in a solvent; 'like dissolves like' principle.

Melting point

The temperature at which a solid becomes a liquid.

Boiling point

The temperature at which a liquid becomes a gas.

Electronegativity

A measure of an atom's ability to attract electrons in a bond.

Surface tension

The tension of the surface film of a liquid caused by intermolecular forces.

Viscosity

A measure of a fluid's resistance to flow.

Partial charges

Uneven distribution of electron density resulting in regions of slight positive and negative charge.

Open lattice structure

Arrangement of molecules in solid form that can trap air, making it less dense.

Fluctuating dipole

Temporary charge imbalance in a molecule that induces dipoles in neighboring molecules.

Polar solvents

Solvents that can dissolve polar solutes.

Non-polar solvents

Solvents that can dissolve non-polar solutes.

Strength of LDF

Increases with the size of the molecule; larger molecules have more electrons.

Important unique properties of water

High melting and boiling points due to hydrogen bonding.

Behaviors of hydrocarbons

Hydrocarbons are generally non-polar and experience London dispersion forces.

Group 14 Hydrides

Compounds with a hydrogen bond with elements from group 14, often non-polar.

Physical properties dictated by IMF

Include state of matter, melting/boiling point, hardness, and solubility.

Homework assignments

Specific problems assigned from textbook pages for practice.

Anomaly in boiling point trend

Unexpected results regarding boiling points as size increases by group.

Observations in molecular interactions

The study of how molecules influence one another based on their structure.

Effective molecular interactions

Affects the solubility, viscosity, and boiling/melting points of substances.