Physics Project to Prove that Gases Have Volume

Gases are invisible, but they have volume. This means that the require space to be present and they have weight. The science fair project mentioned below is a simple experiment to prove that gases have volume.
Aim:
To demonstrate that gases occupy space.
Materials Required:
  1. Clear drinking glass(12 oz)
  2. piece of notebook paper
  3. bucket (it must be taller than the glass)
Procedure
  1. Fill the half of the bucket with water.
  2. Now wad the paper such that it takes the shape of a ball and push it to the bottom of the glass.
  3. Then the glass must be turned upside down. The paper wad must remain against the bottom of the glass.If the paper ball falls, make it a little bigger. (Note that you hold the glass vertically with its mouth pointing down. Push the glass into the bucket filled with 3/4th of water straight down. DO NOT TILT the glass when you lift it out of the water.)
  4. Finally remove the paper and observe it.
Results:
We can see that the paper is dry.
Why is it so?
The taken glass is filled with air. When you push the glass into the bucket, the air prevents the water from entering it and thus the paper continues to remain  dry.