Cut out four triangles from a piece of cardboard to serve as stabilizers for your bottle rocket. Turn the bottle upside down and glue these triangles around the neck of the bottle with some hot glue. Position the triangles evenly around the neck of the bottle until the bottle can stand up without tipping over. Let it dry completely.
Fill the bottle about one-fourth full of water.
Use the sewing needle to poke a hole all the way through the rubber bottle stopper and insert the stopper into the neck of the bottle.
Insert the inflating needle into the hole in the rubber bottle stopper and rest the bottle on a hard surface, such as a sidewalk.
Attach the bicycle pump to the inflating needle and begin pumping the bottle with air. When the air in the bottle reaches maximum air pressure, the air will blow the bottle off the bicycle pump. The water in the bottle will propel the rocket up.
Record the results of the launch in a science journal. Make notes about the amount of water you used, how many pumps of air it took to blow the bottle off the bicycle pump and how high the rocket was propelled.
Try the experiment again with different variables to see if you can increase the height of your rocket launch. Add more water to the bottle for the next try, measure the height of the launch and record your results. Then add less water and try the experiment a third time, recording your results in a science journal. You can also try this experiment with different size water bottle and compare results.
Use a camera to take photos of each launch and to record each launch to display with your rocket and the notes from the experiment.