Chapter 11 - intermolecular forces

Occurs between a (+) ion and the (-) end of a polar molecule

Occurs between two polar molecules

Occurs between an H atom directly bonded to an O/N/F atom and the (-) region of an O/N/F atom on a separate molecule

Occurs between the electron clouds of all molecules but mostly between nonpolar molecules

Hydrogen bonding and dispersion forces (no electrons shared)

Dispersion < dipole-dipole < hydrogen < ion-dipole

Molecular size: larger molar mass/size = greater dispersion forces

Molecular shape: Larger surface area/chained = greater dispersion forces

Definite = keeps shape in container

Indefinite = takes the shape of the container

- high density

- definite shape

- definite volume

- strong intermolecular forces

- particles close together/in-compressible

- high density

- indefinite shape

- definite volume

- moderate intermolecular forces

- particles close together/in-compressible

- low density

- indefinite shape

- indefinite volume

- weak intermolecular forces

- particles far apart/compressible

The amount of thermal energy needed (added) to break the intermolecular forces between particles in a liquid and turn it into a gas (vapor)

The loss (removed) of thermal energy needed for particles in a liquid to slow down and turn into a solid

stronger intermolecular forces (more energy to boil/less heat needs to be removed)

weaker intermolecular forces (less energy to boil/more heat needs to be removed)

the tendency of liquids to minimize their surface area and resist external penetration

- Molecules on the surface of a liquid have stronger IMF with their neighbors and are more densely packed, minimizing their surface area

A liquid's resistance to flow

- Intermolecular forces = stronger attractions makes molecules more resistant to flow

- longer molecular shape = more likely to tangle and resist free flow

- Temperature = almost all liquids became less viscous as temp increases

The ability of a liquid to flow upward against gravity in a narrow tube

- Cohesive: attraction between molecules that keep them together

- Adhesive: attraction between molecules and the surface of the tube

- The adhesive forces are greater than the cohesive forces

- concave (bulging upward)

Liquid phase to gas phase

Gas phase to liquid phase

1) temperature increases

2) surface area increases

1 - volatile (think alcohols)

2 - nonvolatile (think oils)

Amount of heat energy needed to vaporize 1 mole of a liquid

- The amount of heat added to vaporize a liquid is equal to the amount of heat removed for it to condense (H condensation = - H evaporation)

- A dynamic equilibrium is when a liquids rate of evaporation = its rate of condensation in a container

- The pressure exerted by the vapor is the vapor pressure

- vapor pressure depends on the particular IMF in a liquid and its temp

- Weaker IMF = higher V.P / Stronger IMF = lower V.P

When the air pressure above a liquid equals its vapor pressure at that temperature

- As temperature increases vapor pressure increases

- Even small temp increases have a big impact on vapor pressure

- higher altitude/lower atm. pressure lowers the boiling point of many liquids

1 - The heat of vaporization if given 2 measures of vapor pressure and temperature

2 - The vapor pressure at any temperature if given the heat of vaporization and normal boiling point

3 - The normal boiling point if given heat of vaporization and 1 measure of vapor pressure and temperature

Solid phase to liquid phase

Amount of heat energy needed to change 1 mole of a solid to a liquid

- The amount of heat added to melt a solid is equal to the amount of heat released for it to freeze (H freezing = - H melting)

1 - at the beginning until it reaches its melting point

(temp is steady)

2 - after the solid is completely melted (and begins liquefying)

1 - at the beginning until it reaches its boiling point

(temp is steady)

2 - after the liquid completely boils (and begins turning into a gas)

Solid phase directly to gas phase

Gas phase directly to solid phase

vaporization and melting = endothermic (added)

freezing and condensation = exothermic (released)

- It becomes the strongest molecular force

1) Plug in values and convert C to K

2) Convert R to 0.00831 KJ/mol

3) Solve equation(s) on right side

4) Raise both sides to e^ to cancel ln

5) Times both sides by P₂ to cancel P₂ on left side

6) Isolate P2 on the right side by dividing both sides by the attached value

Direct transfer of heat through a solid

heat transfer through fluid motion (Liquid or gas)

Transfer of heat through electromagnetic waves without a medium