One day in chemistry class, andrew told us that some gases makes air, which makes hot air balloons stay in the air. We got candles, plastic bags, and lit the candles. Now we tied the candles to sticks, which were holding the plastic bag. When the candles were lit, the plastic bags would go into the air. It was pretty cool to learn that some heat can generate air. The reason it was floating was because the air was trapped in the balloon, which made it float.