chm 116 intermolecular forces

Dispersed phase

Molecules are far apart (gases)

Condensed phase

Molecules are closer together (liquids and solids)

Intramolecular bonds

Bonds within a molecule

Intermolecular bonds

Bonds between molecules

List weakest to strongest intermolecular forces

London disperson, dipole-dipole, hydrogen bond, ion-dipole, ionic bond

Polarizability

The ability of an electron cloud to distort from changes in charge, affecting intermolecular forces

Higher molecular weight —> ? boiling point

Higher

Larger atoms —> ? electron clouds

Larger

Larger atoms —> ? polarizable

More

More polar —> ? boiling point

Higher

What elements can H bond to in hydrogen bonds?

F, O, and N

What does ion-dipole interactions allow ions to do in polar solvents?

Ions can dissolve in polar solvents

Viscosity

Resistance of the flow of a liquid (thickness)

Surface tension

Difference in surface energies between 2 substances

What is surface tension a result of on a molecular scale?

Net inward force experienced by molecules on the surface of a liquid

Capillary action

A liquid’s ability to “crawl” up surfaces

What 2 forces affect capillary action?

Adhesive and cohesive forces

What phases does sublimation change?

Solid —> Gas

What phases does deposition change?

Gas —> Solid

Heat/Enthalpy of Fusion

The energy required to change a solid to a liquid

Heat/Enthalpy of Vaporization

The energy required to change a liquid to a gas

Heat/Enthalpy of Sublimation

The energy required to change a solid to a gas

What is the equation for heat/enthalpy of sublimation?

Heat of fusion + heat of vaporization

Heating curves

Graphs that show the required amount of energy to raise the temperature and change the phase of a substance

What is the equation for non-phase changes?

q = mCAT

What is the equation for phase changes?

q = (n)(delta H…)

How do you find the total amount of energy needed to change a substance from a solid to a gas?

Add all the sections’ energies together

Vapor pressure

The pressure that gas molecules exert around a liquid/solid when in equilibrium

Higher temperature —> ? vapor pressure

Higher

Higher vapor pressure —> More liquid molecules “?”

Escape

Vapor pressure shows the relationship between vapor pressure and ____?

Temperature

Volatile

A substance that easily vaporizes

Triple point on phase diagrams

An equilibrium point when a substance can have solid, liquid, and gas equally

Increase temperature on liquid —> ? density

Lower

Increase pressure on gas —> ? density

Higher

Critical point on phase diagram

The point when the density of a liquid equals the density of a gas (cannot distinguish liquid and gas)

Supercritical fluid

Anywhere beyond the pressure and temperature of the critical point

What can supercritical CO2 be used to extract?

Caffeine