Assumptions of the kinetic molecular theory of ideal gas .

Gases are made up of independent particles (atoms or molecules) moving in rapid motion in a straight line .
The molecules/ atoms exert no attractive or repulsive forces between them .i.e they are independent.
When the atoms collide with others or with any surface, there is no loss of velocity ( momentum is conserved) , the collisions are perfectly elastic.
The particles are viewed as being relatively far apart and their volumes relatively small (negligible) compared to their total volume of the container, the gas can only occupy 0.03% of the total volume e.g for I mole of a gas at STP.
The pressure is due to the impact of the molecules/atoms on collision with the walls of the container.