This simple demonstration will show that air has weight, and you can even measure it. You'll need a triple-beam balance, some tape, and a big balloon. First, attach a piece of tape to the pan of the balance. You'll be sticking the balloon to this, later. Put the uninflated balloon on the scale too. Balance the scale so the indicator is centred. Blow up the balloon as large as you can. Attach it to the tape on the scale. You will immediately notice that the pan falls, and the scale is no longer in balance. Since the only thing that's been added to the pan is the air in the balloon, the imbalance represents the weight of the air you've added! If you're careful, you can bring the pan into balance again and record how much mass you had to add to do it. That will represent the weight of the air in the balloon. Our thanks to Mark Centazzo and his wonderful 'Whiz-Bang' demonstrations, for the idea for this page. Resources