Why do real gases deviate from ideal behaviour, and under what conditions is the deviation least?

The kinetic theory assumes that molecules have negligible volume and exert no forces on one another. At high pressure the molecular volume is no longer negligible compared with the container, and at low temperature the intermolecular attractions become significant. The deviation is therefore least at low pressure and high temperature.

No citable source has been recorded for this record. Treat it as practice material, not as fact.

Explanation

The van der Waals equation corrects for both effects.