The kinetic-molecular theory of gases makes some simplifying assumptions about the behavior of gas molecules. These assumptions break down under certain conditions, limiting the theory's usefulness.

Here are two conditions that can limit the usefulness of kinetic-molecular theory:

1. High Pressure: The theory assumes negligible volume of gas molecules compared to the container volume. At high pressure, molecules are packed closer together, and their volume becomes a more significant factor, leading to deviations from ideal gas behavior.

2. Low Temperature: The theory assumes that gas molecules have negligible intermolecular forces. At low temperatures, molecules move slower, and intermolecular forces become more significant. These forces can cause deviations from ideal gas behavior, such as condensation.

Important Note: While these conditions limit the theory's accuracy, it's still a powerful tool for understanding and predicting the behavior of gases in many situations. It provides a fundamental framework for understanding the relationship between macroscopic properties (pressure, volume, temperature) and microscopic properties (molecular motion, intermolecular forces).