Understanding Intramolecular and Intermolecular Forces

Intramolecular force

The strong force that holds atoms together within a molecule (e.g., covalent or ionic bonds).

Intermolecular force

The weaker force that holds separate molecules together (e.g., dipole-dipole, hydrogen bonding, London dispersion).

Dipole-Dipole force

An intermolecular force that happens between polar molecules, where the positive end of one molecule attracts the negative end of another.

Hydrogen bonding

A strong type of dipole-dipole force that occurs when hydrogen is bonded to nitrogen (N), oxygen (O), or fluorine (F).

London dispersion

The weakest intermolecular force caused by temporary shifts in electron clouds, found in all molecules but especially important in nonpolar ones.

Ionic bond

A strong bond between a metal and a nonmetal where electrons are transferred, creating positive and negative ions.

Metallic bond

A bond between metal atoms where electrons move freely, allowing metals to conduct electricity and be malleable.

Polar

A molecule with an uneven distribution of charge, meaning it has a positive and a negative end (like water).

Nonpolar

A molecule with an even distribution of charge, meaning it has no distinct positive or negative ends (like oil).

Boiling point

The temperature at which a liquid turns into a gas. Stronger intermolecular forces mean a higher boiling point.

Vapor pressure

The pressure of a gas above a liquid; liquids with weak intermolecular forces have higher vapor pressure because they evaporate easily.

Indefinite shape and volume

Gases take the shape and volume of their container.

Compressible

Gases can be easily compressed due to large spaces between particles.

Low density

Gas particles are widely spaced, resulting in lower density compared to liquids and solids.

Rapid diffusion and expansion

Gases spread out quickly and uniformly in a given space.

Weak intermolecular forces

Gas particles experience minimal attraction to each other.

Definite volume, indefinite shape

Liquids take the shape of their container but have a fixed volume.

Not easily compressible

Particles are closer together than in gases, making compression difficult.

Fluidity

Liquids can flow and take the shape of their container.

Moderate intermolecular forces

Stronger than gases but weaker than solids.

Surface tension

Due to intermolecular forces, liquids form droplets and resist external force.

Viscosity

A measure of a liquid's resistance to flow.

Definite shape and volume

Solids maintain a fixed shape and volume.

Incompressible

Particles are tightly packed, making compression nearly impossible.

High density

Compared to gases and liquids, solids have the highest density.

Rigid structure

Atoms, ions, or molecules are arranged in a fixed, orderly pattern.

Strong intermolecular forces

These forces keep particles in fixed positions.

Molecular size and mass

Larger molecules tend to have higher melting points.

Crystal structure

More ordered structures, like network solids, have very high melting points.

Impurities

The presence of impurities can lower the melting point by disrupting the crystal lattice.

Temperature

Higher temperatures increase vapor pressure as molecules gain kinetic energy.

Molecular weight

Heavier molecules generally have lower vapor pressure.

Volatility

Substances with weak intermolecular forces have higher vapor pressure (e.g., acetone vs. water).

Network solid (diamond)

Extremely strong covalent bonding throughout the structure.