Attractive forces and size effects of molecules in a gaseous system can be neglected at

Attractive forces and size effects of molecules in a gaseous system can be neglected at high temperatures and low pressures.

Here's why:

1. High Temperature: At high temperatures, the kinetic energy of the gas molecules is high. This means the molecules are moving rapidly and are likely to be far apart from each other. The distance between the molecules is so large that the attractive forces between them become negligible.

2. Low Pressure: At low pressures, the gas molecules have more space to move around. This means that the molecules are not close enough to each other for their sizes to have a significant effect.

Therefore, under conditions of high temperature and low pressure, we can make the ideal gas assumption where we neglect the size of the gas molecules and the intermolecular forces between them.