Ideal Gas
A hypothetical gas whose particles have zero volume and exert no intermolecular forces, obeying pV = nRT exactly at all conditions.
Formula / equation
pV = nRT
Unit
Dimensionless
In depth
No real gas is ideal, but all approach ideality at low pressure and high temperature, where molecules are far apart and moving fast enough for attractions to be negligible. The ideal model is accurate enough for most laboratory calculations near ambient conditions.
Examples in the real world
Helium and hydrogen behave almost ideally at room temperature because their intermolecular forces are very weak.