While working on our Wright Brothers project earlier this fall we did a lot of fun activities out of the book Planes, Gliders, Helicopters and Other Flying Machines. One that the kids enjoyed was the Hot Air Balloon experiment we did when we were talking about lighter than air flying.

What you need… small plastic bottle, balloon, heat safe bowl and a kettle/pot. Stretch the balloon over the opening of the empty bottle. Note how it hangs down. Talk about what is in the bottle. This isn’t necessarily apparent to young kids. Even an empty bottle has air in it. Predict what will happen when the air gets hot. Heat water. Test your prediction by placing the bottle in a heat safe bowl filled with hot water (mom should do this for safety reasons). You will have to hold the bottle down… empty bottles like to float… but that is another experiment ;). Watch as the balloon inflates. Talk about why and then predict what will happen when you place it in the freezer.

We ended up going back and forth from hot to cold several times as the kids were fascinated with this experiment. We did this experiment a couple weeks ago but I didn’t get a chance to blog about it so we are using it as our entry for the Unplugged Challenge Theme B.