Mistake Master

Deviation from the Ideal Gas Law

▶︎  Watch it animatedinteractive step-through · ~3 min · optional

The ideal gas law assumes particles have no volume and no attractions — assumptions that fail for real gases at high pressure (particle volume becomes significant) and low temperature (intermolecular attractions dominate). Under those conditions, measured behavior deviates from what PV = nRT predicts.

UNIT 3 TOPIC 3.6 • DEVIATION FROM IDEAL GAS LAW REAL VS. IDEAL Real gases deviate from the ideal gas law (PV = nRT) because of intermolecular attractions and finite particle volume. IDEAL GAS ASSUMPTIONS Particles have no volume No intermolecular attractions Compression factor PV nRT ≈ 1 Behaves ideally REAL GAS REALITIES Particles have finite volume Intermolecular attractions exist Compression factor PV nRT ≠ 1 Deviates from ideal ! WHAT INCREASES DEVIATION? LOW TEMPERATURE ↓ kinetic energy → attractions dominate HIGH PRESSURE particles crowd → finite volume dominates COMPRESSIBILITY (PV/nRT vs P) >1 1 <1 PV nRT T high T low Pressure (at constant T) THE TAKEAWAY Attractions pull particles together → PV/nRT < 1 (strongest at low temperature) Finite volume takes up space → PV/nRT > 1 (strongest at high pressure) CED ANCHOR Gases behave most ideally at high T and low P. (SAP-7.A) AP Chemistry · Unit 3 · Properties of Substances & Mixtures
Real gases deviate from PV = nRT when the ideal assumptions fail: at high pressure the particles' own volume matters, and at low temperature intermolecular attractions pull particles together. Both conditions push the compression factor away from the ideal value of 1.
Real vs Ideal · Open the sandbox →

The trap is misattributing the deviation — blaming the wrong condition, or reading the particle model incorrectly. Deviation grows precisely where the ideal assumptions break: crowd the particles (high P) or slow them down (low T) and their real volume and attractions start to matter.

The work

3 ways in · any order
Lesson
Real vs Ideal Gases

Real gases deviate at high pressure and low temperature, where particle volume and attractions matter. The lesson ties each ideal assumption to the condition that breaks it, then closes with a ten-scenario check.

Skill check · 10 scenarios
Diagnostic
10-item topic check

Ten items on real-gas deviations: identifying when the ideal assumptions fail, and correctly attributing deviations to particle volume (high P) or attractions (low T).

Not started · 10 items · ~15 min
Targeted Practice
Drill a single misconception

Pick one of the failure modes you missed and drill it on its own. The round is adaptive: two correct in a row clears the misconception and moves you to the next.

Take the diagnostic to identify your misconceptions