Ideal gas law
MCAT glossary · Chemical & Physical Foundations of Biological Systems
Definition
PV = nRT (R = 0.0821 Lcdotatm/molcdotK); valid for low pressure and high temperature; deviations described by van der Waals equation.
Ideal gas law in plain English
The ideal gas law, PV = nRT, is one tidy equation linking how squeezed a gas is (Pressure), how much room it fills (Volume), how many gas particles you have (n, in moles), and how hot it is (Temperature); R is just a fixed conversion number (0.0821 in these units) that makes the units agree. The big idea: gases are mostly empty space with tiny particles zipping around, so their behavior is surprisingly predictable — heat them and they push harder or expand; add more particles and the same happens. It's "ideal" because it pretends particles have no size and don't stick to each other, which is nearly true when a gas is spread thin (low pressure) and warm (high temperature). When a gas gets cold and crowded those pretends break down, and the fancier van der Waals equation patches in corrections for particle size and stickiness.
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