A hot air balloon works because the hot air inside the balloon is lighter or less dense than the air surrounding the balloon, causing the balloon to float. You can apply this principle to make your own hot air balloon. Take a black trash bag, fill it with air (a blow dryer is the fastest way), and tie off or securely tape the balloon closed.
Take the trash bag balloon outdoors on a cool, sunny day. The black trash bag will absorb heat. The air inside the bag won't be able to dissipate heat very well, thanks to the greenhouse effect. The hotter air inside the bag will cause your homemade balloon to rise!
Do you think you can get this project to work with a white trash bag? Why/why not?
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