Do some gases weigh more than others? We'll soon find out. Using a balance scale with an empty glass on each side, we will compare the weights of air (the kind that hangs around
for us to breathe) and carbon dioxide.

Carbon dioxide can be produced in a flask, as shown in Project Number C131.10.

When the jar of carbon dioxide, made as C131.10 instructs, is full, take the jar out of the dish and slowly pour the carbon dioxide into one of the glasses. You will see the balance tip as the carbon dioxide goes into the container.

That probably means that carbon dioxide weighs more than air.