Trash Bag will be fly
Hold the mouth of a black trash bag in one hand. Use a hair dryer to blow hot air into the bag.
Seal the mouth of the bag with tape. Tie a long piece of string around the tape so you can hold it. Take the bag out into the sun. The bag will rise slowly into the air. (It’s best to do this trick in an open area on a windless day.)
How Does It Work?
Since the bag is black, it absorbs heat from the sun. That heat makes the air inside the bag expand and become lighter. When the bag and the air inside are lighter than the surrounding air, the bag starts to rise.