Between collisions molecules exert no attractive or repulsive forces on one another.
Gases consist of particles which are very far apart compared to their own sizes.
The pressure exerted by the gas is due to molecules striking the container walls. The average kinetic energy of gas molecules is directly proportional to the temperature of the sample. The average kinetic energy of molecules of different gases are equal at a given temperature. The average speed of gas molecules is directly proportional to the square root of the temperature. The average speed of molecules of different gases are equal at a given temperature.