Gather the materials you need to make your vinegar and baking soda-powered boat.
Carefully cut a small hole in the bottom of the bottle, near to one edge. Note: This is a grownup step. Then, cut a piece of the straw and poke it through the hole. Seal up the hole around the straw with hot glue or packing tape. You want the only path out of the bottle to be down the straw without any other leaks. Safety note: Do NOT try this experiment without the hole for the straw. If there isn’t a way for the gas inside the bottle to escape, the pressure can build up to dangerous levels and cause the bottle to explode.
Hold the bottle close to level and pour in some vinegar. If you rotate the bottle so the straw is at the top, the vinegar won’t leak out.
With the bottle still level, spoon in some baking soda. Hold the bottle steady so the baking soda doesn’t drop into the vinegar.
Screw the bottle cap back on. Tip the bottle to combine the vinegar and baking soda. Immediately place it into a tub of water with the straw under the water. Watch your soda bottle boat go!
What’s going on?
If you mix baking soda and vinegar, you get a chemical reaction which creates carbon dioxide gas. When this happens inside your bottle boat, the gas only has one way to escape, and that’s out the straw. The gas flying down the straw and out the back pushes the boat forwards. This is the same principle used by airplane jet engines. Hot gases are thrown backward out of the engine, and that propels the airplane forward.