Chemistry Rocket (Acid/Base Reaction)
The classic combination of vinegar and baking soda launches a homemade, table-top rocket.
When you think of mixing vinegar and baking soda, you probably recall homemade volcano demonstrations at school and wonderful, stinking messes in the kitchen sink at home. Don’t let these common experiences put you off of the true potential of this classic acid/base reaction. With the Chemistry Rocket activity, you’ll see just how explosive and exciting the combination of these simple components can be in the right setting.
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- 16 oz (473 ml) plastic bottle
- Rubber stopper (to fit the bottle opening)
- Tablespoon measure
- Baking soda
- Strong tape (e.g. duct tape)
- Three new pencils
- Small kitchen funnel
- White vinegar
- Paper towels
- Adult supervision
Use the scissors to cut about 12” (30 cm) of the strong tape from the roll. Duct tape is probably the best choice but you can use electrical or heavy masking tape as well.
The pencils will be the legs of the rocket. Stick one end of the tape to the middle of the bottle but don’t wrap it around the bottle, yet. Hold one pencil onto the bottle so about 2” (5 cm) of it extends beyond the opening of the bottle and keep it in place with the tape. The pencils need to be equidistant from each other around the bottle and extend past the opening the same distance. Wrap the tape over the second pencil and then the third. Make sure the rocket is stable and points straight up on its three pencil legs.
Turn the bottle right side up and use the funnel to pour in some vinegar. You want the bottle to be about half-full.
Grab a single paper towel from the roll. If there are multiple layers in the towel, separate them so you have just one thin layer. Keep the other layer(s) for upcoming launches.
Tear the single layer into thirds or fourths and save the pieces for more tests.
Scoop a heaping tablespoon (1 T) of baking soda and . . .
. . . dump it into the center of the piece of towel you tore off.
Fold and wrap the towel around the baking soda so it’s a snug bundle but don’t tear the towel if you can help it. The bundle needs to be small enough to fit through the opening of the bottle so shape it like a miniature hot dog. Grab the bottle, the bundle of baking soda, the stopper, and take it all outside. DON’T do the next Step inside – please! Your parents and teachers will appreciate your thoughtfulness, you’ll have less to clean up, and everyone will be impressed with the launch.
Outside where you can make a mess safely and clean it up with a hose, you need to think about how to do the next five steps kind of all at once to achieve a successful launch. You need to:
- Push the paper towel-wrapped baking soda into the bottle
- Snugly twist the rubber stopper into place in the opening of the bottle
- Give the rocket a quick, hard shake
- Set the rocket upright on the pencils
- Stand back!
See? Easy-peasy. And what a blast! How can you resist? Do it again!
How Does It Work
What happens when you mix vinegar with baking soda? There’s a lot of bubbling and foaming! The bubbles and foam you see are filled with carbon dioxide gas (CO2) that’s being released by an acid/base reaction. Vinegar is acetic acid dissolved in water and baking soda is a base called sodium bicarbonate. Initially, the reaction makes carbonic acid which is unstable. It quickly breaks down into CO2 and water. The gas then rapidly leaves the water creating foam and bubbles along the way.
When you close the bottle with the rubber stopper, you prevent the CO2 from immediately escaping the bottle. This causes a rapid increase of pressure inside the bottle. The pressure eventually gets to the point that the rubber stopper can no longer contain the gases and – WHOOOOOOSH! – the stopper and the contents of the bottle explode through the opening. It doesn’t take long to get there, either.
As the contents of the bottle shoot downward, the bottle itself shoots upward. How does that happen? This is a demonstration of Newton’s Third Law of Motion: for every action, there is an equal but opposite reaction. The initial action is the rush of material and force out of the opening going one way pushing hard against the air behind the bottle. The reaction is the air pushing back with the same amount of force going the other way. The bottle is thrust forward as the rushing foam and gas shoot backward.
Take It Further
Test different quantities of baking soda and vinegar to lengthen the flight time and distance. Work with different sized plastic bottles, too. You’re looking for the perfect combination of bottle size and fuel to achieve the best launch at the highest speed (distance divided by time). A higher flight, means figuring out the best combination of vinegar to baking soda to produce the most explosive reaction. There may be modifications you can make to the bottle so it travels farther as well. Do some research on the Venturi Effect and see how that might improve things. Maybe the temperature of the vinegar you use will make a difference. There’s “science fair” written all over this activity.