At high pressure, gases deviate from ideal behavior because the assumptions of the ideal gas law no longer hold.
Reasons for deviation at high pressure:
- Finite volume of gas molecules
- Ideal gas law assumes gas molecules have no volume.
- At high pressure, molecules are forced closer together, so their own volume becomes significant, reducing the free space for movement.
- Intermolecular attractions
- Ideal gases are assumed to have no forces between molecules.
- At high pressure, molecules are very close, so attractive forces pull them together, lowering the pressure they exert on the container.
Effects on gas behavior:
- The measured pressure is less than predicted by the ideal gas law because attractions slow the molecules down.
- Gases may condense into liquids if the pressure is high enough.
- Corrections for these effects are included in the van der Waals equation for real gases.
In simple words:
At high pressure, gas molecules get very close, so their size and attraction matter, making them behave differently from the “perfect” ideal gas.