Unit 4: Intermolecular Forces and States of Matter

Flashcards covering key concepts related to intermolecular forces, their types, properties of liquids, phase changes, and associated energy changes.

Intermolecular Forces (IMFs)

Forces that exist between molecules and are weaker than ionic or covalent bonds.

Dipole-Dipole Forces

Forces that are effective when polar molecules are close together; they arise from the attraction between the positive end of one dipole and the negative end of another.

London Dispersion Forces

The weakest intermolecular force that occurs in all molecules, including nonpolar ones, due to momentary dipole moments created by the movement of electrons.

Hydrogen Bonding

The strongest intermolecular force occurring between a hydrogen atom and highly electronegative atoms like nitrogen, oxygen, or fluorine.

Polarizability

The ease with which the electron cloud in a molecule can be distorted, influencing the strength of London Dispersion Forces.

Boiling Point

The temperature at which the vapor pressure of a liquid equals the external pressure, influenced by the strength of intermolecular forces.

Melting Point

The temperature at which a solid becomes a liquid, also related to the strength of intermolecular forces.

Viscosity

The resistance of a liquid to flow; as intermolecular forces increase, viscosity also increases.

Surface Tension

The energy required to increase the surface area of a liquid, directly related to intermolecular forces.

Phase Changes

Transitions between solid, liquid, and gas states that involve energy changes and different strengths of intermolecular forces.

Molar Heat of Fusion (ΔHfus)

The heat required to melt one mole of a solid into a liquid.

Molar Heat of Vaporization (ΔHvap)

The heat required to vaporize one mole of a liquid into a gas; typically larger than the molar heat of fusion due to complete severing of intermolecular interactions.