A real gas behaves like an ideal gas when the effects of intermolecular forces and molecular volume are negligible. This happens under specific conditions:
Conditions for Ideal Gas Behavior
- Low Pressure
- At low pressure, gas molecules are far apart.
- The volume of individual molecules is very small compared to the total volume of the gas.
- Intermolecular attractions or repulsions become negligible.
- High Temperature
- At high temperature, gas molecules move very fast.
- The kinetic energy overcomes intermolecular attractions.
- Molecules behave independently, like in the ideal gas model.
- Non-polar, Light Gases
- Gases like hydrogen (H₂), helium (He), nitrogen (N₂) behave more ideally than heavy or polar gases.
- This is because they have weak intermolecular forces (London dispersion forces).
In simple words:
A gas behaves ideally when it is “spread out and moving fast”, so the molecules don’t feel each other much and the space they occupy is small compared to the container.