Gen Chem II - Chapter 10

Intramolecular Forces

Inside a molecule; covalent, ionic, metallic bonds

Intermolecular Forces

Between separate particles; london dispersion forces, dipole-dipole, ion-dipole, hydrogen bonding

Higher IMF means…

Higher boiling point, higher melting point, higher viscosity, higher surface tension, lower vapor pressure, slower evaporation

London Dispersion Forces

the weakest type of intermolecular force, arising from temporary dipoles in molecules due to fluctuations in electron distribution, present in all atoms and molecules. / attractions caused by temporary changes in the location of electrons

What makes dispersion forces stronger?

greater polarizability, larger molar mass, larger particle size, and molecular shape

Dipole-Dipole

force that occurs between polar molecules

A polar molecule has…

a partially positive end and a partially negative end

Hydrogen Bonding

a strong type of dipole-dipole attraction where hydrogen is directly bonded to N, O, F

The general strength order of the three main forces for similarly sized substances is

London dispersion < dipole-dipole < hydrogen bonding

Ion-dipole

an attraction between an ion with a full charge and a polar molecule with partial charges

General Order of Strength

dispersion < dipole-dipole < hydrogen bonding < ion-dipole < ion-ion

Boiling point

the temperature needed for a liquid to become a gas

Viscosity

a liquid’s resistance to flowing, can be affected by temperature

Surface Tension

the energy required to increase the surface area of a liquid

Cohesion

the attraction between similar substances

Adhesion

the attraction between different substances

Meniscus

the curved surface of a liquid in a container

Capillary Action

the movement of a liquid through a narrow space, sometimes against gravity

Vaporization

the change from a liquid into a gas

Evaporation

vaporization that occurs only at the surface of a liquid

Condensation

the change of a gas to a liquid

Dynamic Equilibrium

rate of evaporation = rate of condensation

Vapor Pressure

the pressure exerted by vapor above a liquid

Volatility

describes how easily a substance vaporizes

Boiling

occurs throughout a liquid when vapor pressure = external pressure

What are the six phase changes?

melting or fusion, freezing, vaporization, condensation, sublimation, deposition

Exothermic Phase Changes

freezing, condensation, and deposition

Endothermic Phase Changes

melting, vaporization, sublimation

Molar enthalpy of fusion

the heat required to melt one mole of a substance at its melting point

Molar enthalpy of vaporization

the heat required to vaporize one mol of liquid at its boiling point

Heating Curve

shows how the temperature of a substance changes as heat is added

Phase Diagram

In the sloped section of a heating curve…

temperature and kinetic energy change, phase stays the same (q = mc∆T)

In the flat section of a heating curve…

phase and potential energy change, two phases are present (q = n∆H)