Beakman weighs a slightly deflated basketball, pumps it up with air, and weighs it again to prove that air has weight. He explains that different gases have different densities, and to demonstrate this, he uses two shopping bags hanging from opposite ends of a suspended stick. He uses a pitcher to collect CO2 gas coming off of dry ice. When he pours the CO2 into one of the shopping bags, that bag's side of the balance goes down, illustrating that CO2 is denser than air and that different gases have different densities.