holds particles back
⚗️AP CHEMISTRY STUDY GUIDE
Intermolecular Forces and Properties
Connect molecular structure to boiling point, solubility, vapor pressure, and chromatography.
8 key ideas8 flashcards5 practice questions
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Particles move according to competing attractions.
different travel rates
carries particles forward
Key ideas to know
Start with the relationships between ideas. Then close the notes and explain each one from memory.
- 01
London dispersion forces occur in all atoms and molecules.
- 02
Dipole-dipole attractions occur between polar molecules.
- 03
Hydrogen bonding occurs when hydrogen is bonded to nitrogen, oxygen, or fluorine.
- 04
Stronger intermolecular forces usually raise boiling point.
- 05
Like dissolves like is a useful starting rule for solubility.
- 06
Ion-dipole attractions occur between ions and polar molecules and often assist ionic dissolution in water.
- 07
Polarizability rises when an electron cloud is larger or more easily distorted.
- 08
Surface tension reflects cohesive attractions at a liquid surface.
PART OF THE AP CHEMISTRY GUIDE
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Open the full AP Chemistry guide →Two ideas worth correcting now
NOT QUITE
→Hydrogen bonding occurs whenever a molecule contains hydrogen
USE THIS INSTEAD
The hydrogen must be bonded to nitrogen, oxygen, or fluorine for the usual course definition.
NOT QUITE
→A larger molecule always has stronger attraction
USE THIS INSTEAD
Geometry, polarity, and polarizability all affect attraction.
Flashcards
Answer before opening each card. The effort to retrieve is part of the learning.
1Which intermolecular force exists in every substance?Show answer ＋
London dispersion forces.
2When does hydrogen bonding occur?Show answer ＋
When hydrogen bonded to N, O, or F is attracted to a lone pair on N, O, or F.
3How do stronger attractions affect vapor pressure?Show answer ＋
They lower vapor pressure at a given temperature.
4Why do larger nonpolar molecules often boil at higher temperatures?Show answer ＋
Their electron clouds are more polarizable, creating stronger dispersion forces.
5What determines chromatography separation?Show answer ＋
Different attractions to the stationary and mobile phases.
6What attraction acts between an ion and water?Show answer ＋
Ion-dipole attraction.
7How does branching often affect boiling point among isomers?Show answer ＋
More branching usually lowers surface contact and weakens dispersion attraction.
8Why does water bead on some surfaces?Show answer ＋
Cohesion within water exceeds adhesion to that surface.
Explain it in your own words
Use the answer as a check after you have written or spoken your response.
01Why does water have a higher boiling point than hydrogen sulfide?
Water forms strong hydrogen bonds, while hydrogen sulfide does not.
02Which dissolves better in water, methane or methanol?
Methanol, because its polar hydroxyl group can hydrogen bond with water.
03What happens to viscosity when intermolecular attractions grow stronger?
Viscosity generally increases.
04Why can iodine have a higher boiling point than chlorine despite both being nonpolar?
Iodine has a larger, more polarizable electron cloud and therefore stronger dispersion attraction.
05How does chromatography indicate stronger stationary-phase attraction?
The substance travels more slowly or a shorter distance under the same conditions.
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