Strong or Nah?
A liquid has low vapor pressure and high surface tension.
STRONG!!!
A nonpolar molecule like CO₂ interacting with another CO₂ molecule
London Dispersion Forces
Rank: He, Ne, Ar
He < Ne < Ar (increasing size → stronger dispersion)
Pentane evaporates faster than water. What does this indicate?
Pentane has weaker IMFs
A molecule is nonpolar. What is the only intermolecular force present?
London Dispersion Forces
A substance boils at −50°C and evaporates quickly at room temp.
WEAKKKKK
Attraction between HCl molecules
Name the force AND draw a model to support it.
Dipole-Dipole
Rank the following and draw the diagrams:
CH₄, NH₃, H₂O
CH₄ < NH₃ < H₂O
Ethanol partially evaporates, water remains. Compare IMFs.
Water stronger (hydrogen bonding stronger than ethanol’s overall IMFs)
A student claims that all polar molecules have hydrogen bonding.
Using evidence from intermolecular forces, evaluate this claim.
Incorrect; only molecules with H bonded to N, O, or F have hydrogen bonding. Other polar molecules only have dipole-dipole forces.
Two liquids: one is thick and pours slowly, the other is runny.
Which has stronger IMFs and why?
Note: MUST USE THE CORRECT WORD!
Thick liquid; higher viscosity = stronger IMFs
Attraction between water molecules.
Name the force AND draw a model to support it.
Hydrogen Bonding
Which has stronger IMFs: NH₃ or PH₃? Explain.
NH₃; hydrogen bonding present
A liquid forms beads on a surface instead of spreading out. What property and IMF strength?
High surface tension; strong IMFs
A substance requires a large amount of energy to change from liquid to gas.
Explain what is happening at the particle level.
Strong attractions between particles must be overcome. Most likely polar.
A substance has high vapor pressure but low boiling point. Explain IMF strength.
In other words: WHY does this happen?
Weak IMFs; particles escape easily
Is CH3Cl a polar or nonpolar covalent bond? Explain.
CH3Cl is a polar covalent bond due to its electronegativity difference and its asymmetric shape.
Rank: C₅H₁₂, C₃H₈, C₈H₁₈
explain your answer.
C₃H₈ < C₅H₁₂ < C₈H₁₈
A substance dissolves in benzene but not water. What does this tell you?
think of the butter and water
the substance is nonpolar
Why do polar molecules experience dipole-dipole forces?
they have partial positive and negative ends due to unequal electron sharing
Two liquids are placed in identical conditions:
Using evidence from both observations, determine which liquid has stronger intermolecular forces and justify your answer using at least two properties and particle-level reasoning.
Liquid A; high surface tension (beading) and slow evaporation both indicate strong IMFs. Strong attractions between particles make them harder to separate and escape
Two substances both have dispersion forces, but one has a much higher boiling point. Explain.
Larger molecule / more electrons → stronger dispersion forces
A compound has a higher boiling point than another with similar structure. What are TWO possible reasons?
More electrons OR hydrogen bonding OR greater polarity
You are in the lab observing two unknown liquids:
B; high viscosity = strong IMFs
Three substances are tested under the same conditions:
a. Identify the most likely dominant intermolecular force in each substance
b. Rank A, B, and C from weakest to strongest intermolecular forces
c. Justify your ranking