IMF, Physical Properties, and Triple Point Graph 2

Review your Intermolecular Force (IMF) Pogil

Read

Effects of Intermolecular Forces - see slide show to do the reading.

Physical Properties affected by Intermolecular Forces - add this to your notes.

Physical properties commonly discussed when relating to IMFs in pure substances are:

●Melting (Heat of Fusion) and boiling points (Heat of Vaporization) - when molecules go from
solid to liquid or liquid to gas or the opposite direction. Other phase changes are
affected by IMFs as well.

●Vapor pressure - the pressure exerted by gases onto the walls of the container

●Enthalpy of vaporization - energy needed at constant pressure to turn a liquid to gas

●
●Viscosity - thickness of a liquid when it comes to fluid flow

●
●Surface tension - resistance to distortion at the surface of the liquid from poking

●●Solubility - Another one of the effects of intermolecular forces is solubility. The stronger the
intermolecular forces between the solute and solvent, the greater the solubility. The phrase “like
dissolves like” helps predict the solubility of a solute in a solvent. Polar molecules dissolve polar
molecules through dipole-dipole forces, and nonpolar molecules dissolve nonpolar molecules
through London dispersion forces. Polar molecules and nonpolar molecules don’t dissolve well
with each other.

Truong-Son N. · 2 · Jul 5 2018

THE STRONG THE FORCE THE HARDER TO OVERCOME THE

IMFs FORCES

The core principle is that the stronger the IMFs in the sample of

molecules, the more strongly they interact, which means they stick
together more. This leads to the following trends:

Stronger IMF →Higher melting and boiling points (harder to melt and boil)

Stronger IMF →Lower vapor pressure (harder to boil)

Stronger IMF →Higher enthalpy of vaporization ΔHvap (takes more energy at
constant atmospheric pressure to turn liquid to gas)

Stronger IMF →Higher viscosity (a thicker liquid, flows more like molasses)

Stronger IMF →Higher surface tension (more resistant to deformation from poking)

Truong-Son N. · 2 · Jul 5 2018

These properties determine the conditions (temperature
and pressure) that substance change states of matter.

Notice two new terms: Heat of Fusion = melting temperature or

freezing temperature; Heat of Vaporization = boiling point or

condensation

Notice the further the molecules are apart the weaker the IMF become.

Two new vocabulary words.

Entropy is to measure the randomness (aka:
disorder) of activity in a system, on the other hand,
enthalpy is the measurement of the overall amount
of energy in the system.

Note the more random the weaker the IMF.

Strong IMF Medium IMF Weak IMF

​

​Add to your
Notes

Multiple Choice

Which phase has the greatest entropy?

• solids

• Liquids

• Gases

Multiple Choice

What phase of matter has the weakest IMFs?

• Gas
• Solid
• Liquid

Multiple Choice

What phase of matter has the strongest IMFs?

• Gas
• Solid
• Liquid

Explanation
Intermolecular forces and order:

Stronger intermolecular forces tend to hold molecules

closer together, creating a more ordered system with lower

entropy.

Entropy and freedom of movement:

Conversely, when intermolecular forces are weak, molecules

can move more freely (more random or more disorder),

resulting in a higher degree of disorder and increased

entropy.

We discussed the following; add to your notes.

● Intermolecular forces are hydrogen bonding, dipole dipole,

and london dispersion.

● Intramolecular forces are the ionic bonds, and

nonpolar covalent bonds

● Comparing intramolecular forces and the intermolecular

forces we discuss the following from
strongest forces to weakest force
are:

ionic bonds>nonpolar covalent bonds>hydrogen bonding>

dipole dipole>London dispersion.

Endothermic - the system releases heat energy.
Exothermic - the system absorbs heat energy.

Vocabulary of Phase Changes

Phase Change Descriptions:

Melting -- the change from solid to liquid.

Freezing/Fusion -- the change from liquid to solid.

Vaporization -- the change from liquid to gas.

Evaporation -- vaporization from the surface of a liquid.

Boiling -- vaporization from within as well as from the surface of a liquid.

Condensation --the change from gas to liquid.

Sublimation -- the change from solid to gas.

Deposition -- the change from gas to solid.

Reading Triple Point Graphs Phase Changes

●Triple point is the point where all of the phases exist at the same
time.

●A "critical point" on a phase diagram is the specific temperature and pressure combination
at which the distinction between a liquid and gas phase of a substance disappears

Multiple Choice

List the phases for letters A, B, and C (BE CAREFUL, LOOK AT ORDER ON THE DIAGRAM)

• Solid, Liquid, Gas

• Liquid, Solid, Gas

• Solid, Gas, Liquid

Multiple Choice

What phase exist at 500 degrees C amd 50 atm?

• Solid

• Liquid

• Gas

Multiple Choice

What phase exist at 400 degrees C amd 60 atm?

• Solid

• Liquid

• Gas

Multiple Select

What phase change is occurring at 400 degrees C and 67 atm? Check all that apply

• Melting

• Freezing

• Fusion

• Sublimation

• Vaporization

Multiple Select

What phase change is occurring at 200 degrees C and about 34 atm? Check all that apply

• Deposition

• Condensation

• Sublimation

• Vaporization

• Fusion

(No date) Phase diagram of neon the solid-liquid-gas triple point is at (24.56 K,... | download scientific diagram. Available at:
https://www.researchgate.net/figure/Phase-diagram-of-neon-The-solid-liquid-gas-triple-point-is-at-2456K-043-bar-and-the_fig2_360376618 (Accessed: 31 October 2024).

Multiple Choice

At what temperature does fusion occur?

• 10 K

• 24.6 C

• 24.6 K

• 44.5 K

Multiple Choice

What phase(s) occurs at 24.6 K and 0.43 bars?

• solids

• liquids

• gases

• all three - s, l, g

Multiple Choice

What element is this?

• Water

• Zeon

• Neon

Multiple Choice

What variable is on the X axis and the Y axis, consectively?

• Pressure, Temperature

• Temperature, Pressure

• Triple Point, Critical Point

Citation

Liu, D. (2024) Influence of intermolecular forces: ChemTalk ., ChemTalk.
Available at: https://chemistrytalk.org/effects-of-intermolecular-forces/ (Accessed: 30
October 2024).

(No date) Phase diagram of neon the solid-liquid-gas triple point is at (24.56 K,... | download scientific

diagram. Available at:
https://www.researchgate.net/figure/Phase-diagram-of-neon-The-solid-liquid-gas-triple-point-is-at-2456K-043-
bar-and-the_fig2_360376618 (Accessed: 31 October 2024).