holds particles back
🧪AP CHEMISTRY STUDY GUIDE
Unit 3: Properties of Substances and Mixtures
Review intermolecular attractions, solids, gases, solutions, spectroscopy, and separation for AP Chemistry Unit 3.
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 attractions occur in every atom and molecule.
- 02
Dipole-dipole attractions occur among polar molecules.
- 03
Hydrogen bonding occurs when hydrogen bonded to nitrogen, oxygen, or fluorine interacts with a lone pair.
- 04
Stronger intermolecular attraction generally raises boiling point and lowers vapor pressure at a fixed temperature.
- 05
Solubility depends on the relative attraction among solute particles, solvent particles, and solute-solvent pairs.
- 06
The ideal gas law connects pressure, volume, amount, and absolute temperature.
- 07
Beer-Lambert law connects absorbance to concentration and path length.
- 08
Chromatography separates substances through different attractions to stationary and mobile phases.
PART OF THE AP CHEMISTRY GUIDE
See every set in this course and follow a focused review order.
Open the full AP Chemistry guide →Two ideas worth correcting now
NOT QUITE
→Breaking an intermolecular attraction breaks a covalent bond
USE THIS INSTEAD
Intermolecular attractions act between particles, while covalent bonds hold atoms together within a molecule.
NOT QUITE
→A gas at high pressure always behaves ideally
USE THIS INSTEAD
Particle volume and attractions cause greater deviation at high pressure.
Flashcards
Answer before opening each card. The effort to retrieve is part of the learning.
1Which attraction occurs in all substances?Show answer ＋
London dispersion attraction.
2What increases dispersion attraction?Show answer ＋
Greater polarizability, often associated with more electrons and more contact area.
3How do stronger attractions affect vapor pressure?Show answer ＋
They lower vapor pressure at the same temperature.
4What is molarity?Show answer ＋
Moles of solute per liter of solution.
5What equation describes an ideal gas?Show answer ＋
PV = nRT.
6What does Beer-Lambert law state?Show answer ＋
Absorbance equals molar absorptivity times path length times concentration.
7What determines chromatography retention?Show answer ＋
Relative attraction to the stationary phase compared with the mobile phase.
8What is an electrolyte?Show answer ＋
A substance that produces mobile ions in solution or when molten.
Explain it in your own words
Use the answer as a check after you have written or spoken your response.
01Why does water boil at a higher temperature than methane?
Water forms hydrogen bonds, while methane has only weaker dispersion attraction.
02How does doubling absolute temperature affect gas pressure at fixed volume and amount?
The pressure doubles under ideal behavior because pressure is proportional to absolute temperature.
03Why can a calibration curve determine an unknown concentration?
Measured absorbance is compared with standards whose concentrations are already known.
04Why can sodium chloride dissolve in water?
Ion-dipole attractions between water and the ions can compensate for separating ions and water molecules.
05How does paper chromatography separate two dyes?
The dyes move at different rates because they differ in attraction to the paper and the solvent.
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