Hot Air Balloon

Make your own hot air balloon. There is something very cool about things that fly – this homemade hot air balloon is no exception. Suitable for children aged 8+ with adult supervision

You Will Need:

Plastic refuse bag

Hair dryer

Duck / Gaffa tape (or a plastic packing strip)

Safety note: This experiment should only be carried out by adults or under adult supervision. There is a chance the refuse bag will get too hot and start to melt risking a minor burn. The hairdryer could also overheat.

Instructions

Open up the refuse bag and make the bag opening narrow using duct tape or similar. To do this, poke holes in the plastic around the bag opening and thread the tape (or a plastic packing strip) in and out through the holes and secure.

Blow hot air into the bag using the hair dryer directed through the now small opening. Do not leave the hairdryer on for too long or the plastic may start to melt and weigh the bag down.

After a few seconds, when the bag is full of hot air, turn off the hairdryer and let go of the bag. The bag should begin to rise towards the ceiling and hover for some time. When it comes back down, fill the bag with more hot air and let go again. You may have to repeat this a few times before the bag actually reaches the ceiling.

What’s Happening?

The particles, or atoms, making up hot air have more energy and therefore move faster than air at cooler temperatures. Because they are on the move, the hot air particles take up more space in the refuse bag than cooler air particles. This means there are fewer air particles inside the hot air balloon compared to the outside atmosphere. With less particles, the bag is lighter than the surrounding air, allowing it to rise. When the air inside the bag cools down and the particles slow down making more room, this allows more air to enter the bag making it heavier and sinking it to the floor. Real hot air balloons work on this same principle: that hot air rises. Heat is turned up to get the balloon higher and turned down to sink the balloon lower.

Have Fun!

Thanks to, and adapted from madaboutscience.com.au