A demonstration of the compressibility of air versus water is shown using two syringes, one filled with air and the other with water. When a large weight is placed on each syringe, the air-filled syringe compresses significantly, while the water-filled syringe shows negligible compression. This illustrates the stark difference in compressibility between gases and liquids, highlighting that while air is easily compressed due to the large spaces between molecules, water is nearly incompressible because its molecules are closely packed together.