1. When the air inside the balloon gets toasty it turns into a little floating helper that lifts the balloon up, and when it cools it becomes heavy and the balloon drifts back down.
2. Warm air inside the balloon is like a bouncy friend that hoists it into the sky, but when the friend gets chilly it lets go and the balloon comes home.
3. The balloon floats up when the air inside is warm and puffed up, and sinks when that air cools and shrinks like a sleepy pillow.
4. Think of warm air as a tiny elevator that takes the balloon up, and when the air cools the elevator goes back down and so does the balloon.