This project demonstrates how hot air can make a lightweight plastic bag rise, using a hair dryer. The heated air fills the bag, making it less dense than the surrounding cooler air, which causes the bag to lift into the air.

1. Find a very thin, lightweight plastic bag (such as a dry-cleaner bag or thin trash can liner).
2. Hold the bag open at the bottom, keeping the opening wide.
3. Turn on a hair dryer and direct the warm air into the bag, allowing it to inflate.
4. Once the bag is filled with hot air, release it gently and observe how it rises.
5. Repeat with different settings (cool, warm, hot) on the hair dryer to compare results.

How to Make a Mini Hot Air Balloon | Home Science Experiments - Science Max:

Make your own hot air balloons - Curiosity Show:

• Use different sizes and thicknesses of bags to test how mass affects lift.
• Use two hair dryers at once to fill the bag more quickly.
• Compare how long the bag stays aloft depending on how hot the air is inside.

• Keep the hair dryer away from water and avoid overheating.
• Do not use sharp or heavy bags that could tear or fall dangerously.
• Supervise children to ensure the hair dryer is used safely.
• Avoid holding the bag too close to the hair dryer’s heating element to prevent melting.

• Why does the plastic bag rise after being filled with hot air? (Because hot air expands, becomes less dense than cooler surrounding air, and creates lift.)
• How does the size of the bag affect its ability to fly? (Larger volumes can trap more hot air and stay aloft longer.)
• Why does the bag eventually fall back down? (The air inside cools, becomes denser, and can no longer support the bag’s weight.)
• How does this compare to using candles as a heat source? (Candles provide continuous heating, while a hair dryer only heats during filling.)