Bathtub Bottle Rocket
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You know the super fun bottle rocket experiment you can do with baking soda and vinegar (plus a cork)? Â We tried another really cool variation on that activity this past week. We made a bathtub bottle rocket that actually moves through the water. Â It is so easy to make, so save your bottles!
These bathtub bottle rockets, or water rockets, are the perfect homemade science toy for kids. You don’t need any special supplies or ingredients.
How to Make the Bathtub Bottle Rocket
To make this bathtub bottle rocket, Â you need just a few simple supplies:
- Baking soda
- Vinegar
- Empty soda or other plastic bottle
- Straw
- Small piece of clay  (polymer modeling clay works great)
- X-acto knife or other sharp knife
Instructions:
I have done this with white vinegar and red wine vinegar (when I was out of the white kind) and both worked great!
Using a sharp pair of scissors or an ice pick, poke a hole in the side, bottom part of the bottle.
Insert the straw into the bottle and seal it with tape or clay so that air and water do not escape through the hole.
Pour some vinegar into the bottle, about 1/4 to 1/2 cup should do. This will depend on the size of your bottle. A smaller bottler will need less vinegar.
Using a square of toilet paper, scoop a tablespoon of baking soda into the center and fold it up.
When you are ready to let the rocket go, drop the baking soda packet into the bottle. Put the lid back on the bottle, and shake it up.
Fill up the bathtub about half way. Place your bottle rocket into the tub with the straw pointing into the water. You have to act quickly! Â You may want to assign one person to be the rocket launcher and be ready to go. It will blast off quickly.
The bubbles from the reaction between the baking soda and vinegar will bubble out of the straw and make the bottle rocket move across the tub! Â It will have a quick acceleration, then fizzle out and slow down.
Tip: If it isn’t sitting down low enough in the water, you can add a couple of coins or marbles into the bottle to add weight.
Try launching two different bottle rockets at the same time to keep the fun going. You can also experiment with different sizes of bottles. What other variables could you use?
The Science Behind the Bathtub Bottle Rocket:
Anytime baking soda and vinegar react it creates the gas carbon dioxide. The gas creates a change in pressure inside the bottle and it wants to escape. The gas bubbles out of the straw since it is the only opening. This pushes into the water and makes the boat move! Simple and fun.
The bottle rocket is an example of Newton’s Laws of Motion. The first law of motion states that an object will remain at rest unless a force acts upon it. The bottle rocket remains at rest on the launch pad until the force from the pressure inside the bottle when the reaction happens.
Newton’s second law illustrates the relationship between force, acceleration and mass . The amount of force pushing the rocket depends on the amount of force created by the baking soda and vinegar reaction. If you add a little more of either of these to the bottle, it will increase the mass of the rocket.  This then increases the force applied as the gas is expelled from the straw.
The Third Law of Motions states that for every action there is an equal and opposite reaction. This definitely takes place here!
My kids did this bathtub bottle rocket activity a whole bunch of times. It was really a hit in our house. Â Give it a try and see if you can get some races going with a few different bottles.
See More SUPER FUN Science Activities:
Straw Rocket with Printable Template
STEM Project: Cardboard Tube Rocket Blaster
