Balloon Rocket

Materials Required

1. Balloon
2. Straw
3. String
4. Two chairs

Procedure

1. Take the straw and stick it to the balloon and push the string through the straw.
2. Tie two ends of the string to the two chairs.
3. Inflate the balloon and let it go 

Observation and reason

1. The balloon goes woosssshhhhhh.
2. It is because of the imbalance between the two ends of the balloon.