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Popsicle Stick Chain Reaction

Summary

Active Time
30-45 minutes
Total Project Time
30-45 minutes
Key Concepts
Elastic potential energy, energy transformation
Credits
Sabine De Brabandere, PhD, Science Buddies
Popsicle Stick Chain Reaction -STEM activity

Introduction

If you enjoy chain reactions and spectacular sights, this activity is for you! Who knew weaving unspectacular tongue depressors could set off a chain reaction of sticks flying in the air? Try it out and see for yourself!

This activity is not recommended for use as a science fair project. Good science fair projects have a stronger focus on controlling variables, taking accurate measurements, and analyzing data. To find a science fair project that is just right for you, browse our library of over 1,200 Science Fair Project Ideas or use the Topic Selection Wizard to get a personalized project recommendation.

Materials

  • Tongue depressors, at least 50. If these are not available, large somewhat flexible craft sticks are a good alternative. Avoid the thicker, more rigid popsicle sticks.
  • Hard floor
  • Markers, 4 different colors
  • Glue
  • Optional: video camera

Prep Work

  1. Make a piece to start your chain by placing three tongue depressors parallel to each other. Leave about two centimeters between the depressors.
  2. Stagger the parallel depressors so each depressor sticks out two to three centimeters above the adjacent one.

  3. Place a depressor at a right angle to all three depressors. Shift it until it just touches all three depressors, and glue it in place.

  4. Place a second depressor next to it and glue it to all three staggered depressors.

  5. Turn over and glue two depressors on the other side to help keep the three staggered depressors in place.
  6. Number the depressor that sticks out most 1, write 2 on the middle one and 3 on the one that sticks out least. You can color the starting piece with markers as shown below. Colors are not essential but can help you understand how to assemble the chain.

Instructions

  1. To start your chain, have the starting piece that you just assembled and a large number of tongue depressors nearby. You may want to color a few depressors in four different colors as shown in the picture. This may help you get started.

  2. Slip a depressor in the starting piece so it goes under depressor 1, over depressor 2 and under depressor 3.

  3. Slip the next depressor in the starting piece so it goes over depressor 1, under depressor 2 and stops there.

  4. You should see two parallel depressors sticking out.

  5. Slip the next depressor under the shorter one until it sticks out a little, and over the longer one, parallel to depressor 1.
    Think about:
    You might feel you have to hold the depressors in place. Why would this be?

  6. You should see two parallel depressors sticking out.

  7. Slip the next depressor under the shorter one until it sticks out a little, and over the longer one so it makes a right angle with the sticks it crosses.

  8. Find the two parallel depressors sticking out and slip the next depressor under the shorter one until it sticks out a little, and over the longer one so it makes a right angle with the depressors it crosses.

  9. Repeat step 8 to build on.
    Think about:
    Do you feel like you have to bend the depressors? How would that help create an explosive chain reaction? What do you think will happen when you no longer hold down the last couple of depressors you weaved into the chain?
    Interlaced popsicle sticks held down by a hand
    Interlaced popsicle sticks held down by a hand
  10. If finding the two parallel depressors that are sticking out is hard, you can also rely on the colors to build the chain. Notice how in these pictures, the sequence is red, light blue, orange, dark blue and then back to adding a red depressor. In this case, the red depressors always go under a dark blue one and over a light blue one. Orange depressors go over the dark blue and under the light blue ones or light blue depressors go under red and over orange ones, etc.
  11. Keep building until you are satisfied with the size of your creation. You can keep the depressors in place by fixing the last depressor you are adding under the one that would be parallel to it if you were continuing making the chain longer.

  12. Once you are ready, let the last depressor go, but be ready to step back and watch.
    Think about:
    What happens? Why would this happen?
  13. Build longer chains and see how the chain reaction changes as the chain gets longer. If you have a video camera available, take a video of the chain going off, preferably in slow motion.
    Think about:
    What is different and what is similar between a longer and a shorter chain reaction? What can you learn from the slow-motion video?

  14. For a challenge, make your stick bomb make a bend or make it go over obstacles.

What Happened?

You probably saw the depressors jump up in the air as soon as you release the last one, and maybe even before you planned to let them go.

You may have noticed that you had to bend the depressors in order to make them fit into the chain. With each bend, you added energy to the system. Did you feel how the chain was under tension, how you had to hold the last couple of depressors to keep them in place? When you let it go, all this tension is released in a chain reaction. It starts with the last depressors straightening up. This releases the next depressors in the chain, and so on. Soon, all the depressors fly in the air, releasing the energy stored in them and you have a whirlwind of depressors flying around.

Digging Deeper

Energy is never created; it gets transferred from one kind to another. For the stick chain reaction built in this activity, you push each depressor as you bend it to weave it into a chain. The depressors store this energy as elastic potential energy. If you have stretched a rubber band, you have felt how it wants to come back to its original length. Scientists say that a stretched rubber band is loaded with elastic potential energy. In a similar way, the depressors store elastic potential energy when bent. When you allow the stick to go back to its flat state, it releases this energy. When one depressor releases its stored energy, nothing spectacular happens, but when a chain of depressors release their energy, you get a dramatic effect. If the chain reaction happens on a hard floor, the sticks will push themselves off of the floor and fly high into the air. The elastic potential energy is transformed into movement, also called kinetic energy. As they fly up, the depressors gain height above earth, which translates into gravitational potential energy or the energy due to the fact that it can fall to earth. Eventually, the depressors lay flat on the ground. The energy once stored in the chain has been transformed into heat and sound energy.

It is much harder to weave small popsicle sticks together. These popsicle sticks do not bend easily, instead, they tend to break. They are not as well suited to store elastic potential energy. Jumbo popsicle sticks (7 3/4 inch long) are more elastic, they can be woven into a chain and are a nice sight when being released. The tongue depressors (5 3/4 inch long) give the most spectacular result.

If you assemble your chain and leave it out for a day or so, you might notice your depressors do not jump as high when you release the chain. Over time, the depressors yield under the tension and become permanently deformed. Part of the elastic potential energy went into deforming the material.

If you tried to release the chain on carpet or any other soft ground, you might also have noticed the depressors did not jump as high. The depressors cannot bounce off the soft ground that easily because the ground absorbs part of their energy.

Interlaced popsicle sticks held down by a hand
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For Further Exploration

  • Compare the chain reaction exploding on carpet to a similar chain exploding on a hard floor. Which one makes the sticks jump up highest? Why would this be the case?
  • Make chains from jumbo popsicle sticks and tongue depressors. Can you explain why the result is different?

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