How can you show experimentally that a gas produces pressure on the walls of the vessel in which it is located?

Let us consider experiment to prove this property. Place a knotted rubber ball that contains a small amount of air under the bell of the air pump. Then we pump out the air from under the bell, thereby reducing the number of molecules that hit the outer shell of the ball. Under this condition, we will see that the ball begins to inflate, because the number of air molecules that hit the inner walls of the ball has not changed. This experiment shows that las produces pressure on the walls of the vessel in which it is located.