Original: A balloon is filled with hot air and pops up, up, up into the sky!
Corrected (best): A balloon fills with hot air and floats up, up, up into the sky!
Also good: A hot-air balloon fills with hot air and floats up, up, up into the sky!
Why this is better (easy steps):
- We change "is filled" to "fills" so the sentence is active and simple: the balloon does the action.
- We change "pops" to "floats" because "pops" usually means it bursts. "Floats" or "rises" means it goes up gently.
- The phrase "up, up, up" is fine and fun for a child. The exclamation point shows excitement.
Quick tip: Use "floats up" or "rises" when something goes up slowly or gently. Use "pops" only if it bursts.