How can you prove that air is not an empty space?

That air is not an empty space, but has mass, volume, buoyancy and other qualities can be proved in at least two ways.

1. Take a balloon and inflate it. What will you see? You will see how the ball grows in size. This air fills it with its volume. Then release air from the balloon. The air will come out of it with a characteristic sound, which means that it has a buoyancy force.

2. You need to take an empty glass or cup, turn it over and in this position, dip it into a container with water (bowl or bucket). What will you see? And you will see that water will fill a glass or a cup only when they are immersed in water at an angle.