In a gas such as air, the molecules create force By hitting another surface. This hitting action creates pressure. The amount of pressure involves the number of hits and the average incoming momentum of the particles.(The picture is a women airing a balloon up with her mouth). Look at the picture and the passage. How does the picture demonstrate air pressure? A. The more air that is in the balloon, the faster the air particles move, causing the balloon to expand. B. As more air is blown into the balloon, the pressure increases, forcing the sides of the balloon to expand. C. Air particles blown into the balloon or moving faster than the air outside of the balloon, causing it to expand. D. Compressed air from the lungs is blown into the balloon. Because this air is heavy, the balloon expands.