How To Make Soda Bottle Motorboats

When baking soda and vinegar mix, the resulting chemical reaction produces carbon dioxide. Carbon dioxide is present in many aspects of our everyday lives. Some of the most familiar places you've seen carbon dioxide is in soda pop's fizz and in the bubbles in rising bread. A simple experiment that demonstrates carbon dioxide's properties is the ever popular "Soda Bottle Motorboat." This is a good one for kids to try - just supervise them and be sure that everyone wears their safety glasses.

The supplies for this project are commonly available.

  • baking soda
  • vinegar (any type will work)
  • one clean, twenty-ounce soda bottle
  • one sheet of paper towel
  • one thumbtack (optional)
  • one flexible drinking straw (optional)
  • a handful of marbles (optional)
  • modeling clay (optional)
  • one bathtub or wading pool with a few inches of water

Step 1: Take all of the supplies to the bathtub or pool. Once the vinegar and soda mix, the motorboat needs to be placed in the water right away.

Step 2: Tear the paper towel into quarters. Take one of these pieces and put one tablespoon of baking soda in the center. Fold the paper towel around the pile and twist it closed at the top. Try to fold it well so the reaction will be delayed slightly.

Step 3: Pour one half cup of vinegar into the "motorboat." Drop the paper packet of soda inside, and then quickly cap it. Twist the lid only three-quarters of a turn. Do not screw it on tightly.

Step 4: Place the boat into the water. As soon as the vinegar soaks through the paper and reaches the soda, the chemical reaction will begin and the boat will start to move forward. Take notes on what this model did and then try the variations below to see how things can change.

Variation 1: After Step 2 above, use the thumbtack and puncture a hole in the lid. Make a second hole that is large enough for a drinking straw in the end of the bottle. Push the straw a little over 1/4 of the way into the bottle with the short end inside. Press some modeling clay around the opening in the bottle so it is airtight. This will allow the carbon dioxide to only escape through the thumbtack hole in the lid and through the straw and should give the motorboat more power. Continue to Step 3, but screw the lid on tightly this time.

Variation 2: Drop a few marbles into the bottle and see how it affects the bow or stern ends.

Variation 3: Vary the amount of vinegar and baking soda used. Change the ratios. Note the proportions which increase the speed of your homemade soda bottle motorboat.


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