Use The Baloon As Rocket
1 balloon (round ones will work, but the longer "airship" balloons work best)
1 long piece of kite string (about 10-15 feet long)
1 plastic straw
Tie one end of the string to a chair, door knob, or other support.
Put the other end of the string through the straw.
Pull the string tight and tie it to another support in the room.
Blow up the balloon (but don't tie it.) Pinch the end of the balloon and tape the balloon to the straw as shown above. You're ready for launch.
Let go and watch the rocket fly!