Family Science

Build a Rocket

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Science Hobbies RocketImagine sweeping the dust from a giant rock formation to uncover an ancient dinosaur fossil, or peering through your backyard telescope to identify a hazy comet as it streaks across the sky. Sound exciting? Believe it or not, several scientific discoveries were first observed by amateur hobbyists. While most hobbies don’t lead to important breakthroughs, they can be a fun way to learn about science. This is the perfect time of year to explore some new activities. The investigation below will introduce you to the hobby of rocketry. If building rockets isn’t your thing, you might try some other science hobbies, like collecting rocks, observing weather or flying kites. Who knows, your hobby might even turn into a career one day.

Caution: This activity requires adult supervision.

35 mm film canister
effervescent tablets
(such as Alka-Seltzer)
construction paper
(The canister should have a lid that snaps inside the rim. Most white or transparent canisters have this type of lid. The black canisters with the gray lids that snap over the rim will not work.)

To Do:
1.) Find an area outside that is not too crowded and a safe distance from any buildings or trees. A solid surface, such as concrete, works best. (If you plan to launch your rocket in the grass or dirt, put a piece of wood or other hard material on the ground.)
2.) Place the film canister on the ground and fill it approximately 1/3 to 1/2 full of water.
3.) Carefully break your effervescent tablet in half. Set one of the pieces aside for later.
4.) Drop the remaining piece of tablet into the canister and quickly put on the lid.
5.) Turn the canister over so the lid is touching the ground and then stand back!
6.) Watch your rocket shoot into the air.
7.) If your rocket doesn’t fly as high as you would like, launch it again. It takes some practice to get the right technique and the proper amount of the ingredients.

Now Try This:

Can you make your rocket fly higher by altering the shape of the rocket or the ingredients that you add to the film canister? For example, you might fashion a nosecone or fins out of paper and attach them to the canister (see photo above). Or try adding a larger piece of effervescent tablet or a different amount of water. You can even substitute vinegar and baking soda for the water and Alka-Seltzer. Keep investigating until you find the perfect combination.

What’s Going On?
The main ingredients in the effervescent tablet are sodium bicarbonate and citric acid. When the tablet dissolves in the water, these chemicals react to produce carbon dioxide gas. This gas builds up inside the canister until the pressure becomes so great that the lid pops off and the gas rushes out. The escaping carbon dioxide gas pushes against the ground, causing the canister to shoot into the air. This film canister rocket is an excellent demonstration of Newton’s third law of motion, which states, “Every action has an equal and opposite reaction.” The same scientific principle applies to real rockets, except a chemical propellant replaces the effervescent tablet.

Debbie DeRoma is the education manager at the Reuben H. Fleet museum.