Rockets and Launchers

A) Objective: The students are introduced to the concept of chemical reactions that occur when: a) two substances react or b) when one substance undergoes a phase change. The students also get to learn the importance of angles of projection in projectile motion, as they are constructing launchers for their chemically powered rockets. The goal is to make the rocket travel the longest distance.

B) Time: 1 hour.

C) Materials:

• List of Materials:
  1. film canisters with lids
  2. vinegar and baking soda; or dry ice
  3. Goldberg materials (usually "junk" like Styrofoam, scrap paper, paper towel tubes, etc. - see "Rube Goldberg Machines")
• Materials found:
  1. Film canisters and Goldberg materials are usually available as donations from stores and factories. Dry ice may be available at fishing supply stores.
• Cost per student: negligible.

D) Theory:
In this activity, either vinegar and baking soda or dry ice is used to produce gas. Vinegar reacts with baking soda and produces carban dioxide gas, solid carbon dioxide (dry ice) can be used as it spontaneously sublimates into carbon dioxide gas at room temperature. As the chemical reaction occurs, producing gas, pressure is built up in the canister until it is no longer able to contain the gas. At this point, the canister is shot up into the air, the gas is able to escape and the pressure is released.

The forces acting on the rocket are gravity and the force produced by the chemical reaction. The force of gravity has to be opposed by directing the rocket upwards, but at the same time, the force from the gas expansion has to be directed horizontally as to reach maximum distance. This is achieved by a 45 degree launching angle (ignoring the effects of air resistance).

E) Procedure:

1. Divide the students into pairs
2. Give each pair an empty film canister and Goldberg supplies
3. Let the students build their launchers for about 20-30 minutes. Let them try them out with the launching chemicals once during the building process.
4. Launching procedures:

   Vinegar and Baking Soda Method	Dry Ice Method
   Put the vinegar in the canister first. Put the baking soda on a little piece of paper. Drop the paper in the canister. Seal quickly. Putting the soda on the paper allows time to seal the lid before the gas is released. There may be other ways to delay the reaction -- let the kids figure it out!	Do not let the dry ice touch your skin. Scoop up a teaspoon full of dry ice with the canister. Seal the canister See if taking more dry ice into the canister speeds up the reaction or delays the reaction. Why?

5. Line the launchers up and fire the rocket, one at a time. Remember to mark the landing spot for each rocket.
6. Discuss with the students what rockets/launchers worked the best.
7. Tell the students how to use vinegar and baking soda (or dry ice, whichever you are not using) as an alternative to produce carbon dioxide.

F) Safety:
Be careful with the dry ice. Don't let the students touch it and be sure that there is no dry ice left on the launchers before the kids pick them up. Make sure that the area for launching is empty and that the students stay behind the launchers as not to get hit by the rockets. It is recommended that this project be done outside due to the mess that occurs if you are using baking soda and vinegar.