Adan Hussain January 28, 2010

Alka Rockets

Objective: To introduce the concept of pressure and work.

Introduction: Force is what causes mass to accelerate or become deformed. Examples of forces include pushing, pulling, gravity and friction. When force is applied to a surface area, it creates pressure. Pressure is what creates diamonds and dry ice. People can harness pressure to do work. In this activity, the students will harness pressure to launch a rocket.

Vocabulary: Velocity, Force, Pressure, Work, Newton’s Third Law of Motion- For every action there is an equal and opposite reaction

  • Empty, film canister with lid that snaps inside (you can find these in any local film store)
  • Markers, crayons, or colored pencils (and any other materials they can use to decorate their rockets.
  • Dry Ice
  • Construction paper
  • Tape
  • Scissors
  • Alka Seltzer tablets (or any antacid tablet)
  • Re-sealable bags
  • Pipettes
  • Water (optional Vinegar, Lime Juice, and/or other liquids)
  • Bowls or small bins (to make clean up a bit easier)

Safety: Students need to move away from the rocket once they set it down. Some rockets take more time to launch so students may have to wait before they see a reaction. No one should approach a launching rocket unless they are sure from a distance that it leaked, etc.

Demonstration: Put some dry ice into a re-sealable bag and seal it tight. Place a textbook or anything flat and heavy onto the bag. Observe as the bag inflates. This demonstration gives an example of how pressure exerts force. Show them a demo rocket launch afterwards.

Prelab: Answer Pre-lab Questions after demonstrations.

Procedure:

1. Give them construction paper, the canisters, scissors and any other materials they can use to decorate their rockets. Have them cut enough construction paper in order to wrap the canister with the construction paper. They can get as creative as they want. Also, they need to add fins and a cone to the rocket. The fins are simple, but the cone will be harder to make. It would be a good idea to help them make it.

2. They should securely wrap and tape the canister so it does not fall apart when they launch it.

3. The fins and cone come on next. They help the rocket go higher. The canister’s opening should not be covered.

4. The idea of this activity is to experiment with different amounts of water and Alka Seltzer to maximize pressure within the canister. Using the pipettes, they should first fill the canister approximately ¼ full with water and add ½ tablet of Alka Seltzer. It helps if they break up the Alka Seltzer.

5. The students need to snap the canister shut quickly, set it down and move away. They should have enough time to do so.

6. Place the rocket in a bin, lid facing down. Stand back and count down while you are waiting for launch!

7. The students can use measuring sticks to see how high the rocket went, but they will not get accurate numbers. More often than not, the rocket will go higher than what they can measure. They really just need to make visual references and compare the height when they use different amounts of water and Alka Seltzer.

8. They can then use lime juice and vinegar as alternate liquids in combination with the

Alka Seltzer.

Suggestion:

  • Have about 3 volunteers helping. There should be supervision for the rocket launches.
  • While some students launch their rockets, others may have to wait. Give the students an activity they can do while they wait.
  • In case there is not enough time, you can make the rockets and take out lime juice from the activity. You can also change the amount of trials per liquid in the activity.

Expected Results:

If there are no leaks, the rockets should shoot up 4-12ft (1.21-3.67 meters). The less water the better the results. Even 1/8 the canister full works. The idea is to show that more does not mean better. Adding more liquid makes little difference, so more liquid is a hindrance rather than a catalyst. There is only a certain amount of Alka Seltzer that will react before enough pressure builds up, so if there is too much Alka Seltzer, most of it will not have reacted. However, if there was too little, then the rocket will not go as high as it could.

Supplementary Exercises:

Use other acids. Try bases and see what happens.

Design and launch a rocket powered by two, three or more film canisters.
References

Name______

Alka Rockets

Force is anything that changes velocity. Pushing a book across a room or gravity are examples of forces. When force is applied on an object, you create pressure. Pressure can be used to do work for us. In this activity, we will use pressure to launch a rocket.

Pre-Lab:

What happened when the Dry Ice was left inside of the bag?

What would happen if no one let the air out of the bag?

Why did the rocket launch?

Procedure

1. Hold the rocket upside down and squirt in water using the pipette. Repeat as many times as you want. Do not fill the rocket up too much.

2. Ask a nearby adult or partner to help you add Alka Selzter to your rocket. Make sure the rocket is snap shut.

3. Place the rocket in a plastic bin, lid facing down. Stand back and count down while you are waiting for launch!

4. Estimate and record how high your rocket went. Use a measuring stick if you like.

5. Use different amounts of Alka Seltzer and water to see if you can make your rocket go higher

Water / Alka Seltzer / Height
4 squirt / 1 half (1/2)

6. Now try using Vinegar

Vinegar / Alka Seltzer / Height

7. This time use Lime Juice

Lime Juice / Alka Seltzer / Height

What is the best combination of Alka Seltzer and water to produce the maximum launch height? What is your evidence?

What liquid worked made your rocket go the highest? Can you explain why?

What happened when the Alka Seltzer was added to the liquid?

What action happened inside the film canister?

What was the reaction of the rocket?

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