Here’s the post I promised you (and one I’ve been very excited about writing!): Dancing Oobleck!
Right about now you may be asking yourself “What is oobleck?” Oobleck is a Non-Newtonian Fluid. Which basically means it is a substance that can be both a solid and a liquid at the same time.
In preschool terms it is that cool stuff you can make with cornstarch and water that you can form into a ball when you press on it, but drips through you fingers when you let go.
How To Make Oobleck:
The day before we did this experiment, we had made dough in the water table using flour and water, which made for great predictions when I pulled out another white powder (cornstarch) and asked the children to guess what would happen when I mixed it with water.
After the children made their predictions, I went ahead and mixed the solution. My method is usually to mix until it is the right consistency, but if you prefer to measure, it is about one part water to two parts cornstarch. Once I had it mixed up, the children realized it did not make dough. In the bowl, it displayed liquid qualities.
The words solid and liquid have become part of the children’s vocabulary from exposure to these words through other science activities. So, I asked the children if I had made a solid or a liquid. They said liquid. Then I asked them what they thought would happen if I slapped the oobleck with my hand. Expecting it to act like a liquid, they guessed it would splash all over them, and braced themselves as I went to hit it!
With pressure, it is a solid.
When there is no pressure, it is a liquid.
But my hand hit the oobleck as if it were a rock. We then had a discussion on how this acts as both a solid and a liquid. When pressure is applied, it acts as a solid, but when the pressure is released, it acts as a liquid. We also let a toy sink into the bowl of oobleck and saw how it acts like quicksand. The toy got stuck and was very hard to pull out!
Then we moved on to the best part: making the oobleck dance!
How To Make Oobleck Dance:
Oobleck “comes to life” making little mounds and worm-like forms that move up and wiggle around when it is set on a speaker cone with a tone of a certain frequency. I had seen this on YouTube before and had been wanting to make it happen for a good, long time. So I was very excited when I finally decided to try it with the preschoolers. It took a lot of prep time and figuring out before I could do it with the kids. I had so much fun being the scientist at home, tweaking and experimenting until I figured out how to make it work!
I happened to have an old stereo lying around, which worked perfect for this experiment. I popped the plastic cover off the front of the speaker to reveal the speaker cone on the inside. On this speaker, the cover would pop right back on, so it would be possible to do this experiment without ruining the stereo. It can, however, be quite messy, so I would recommend using a stereo you can devote only to oobleck dancing if you can. The experiment can also be done using a subwoofer, but we had better luck with the speaker.
The hardest part was figuring out what frequency I needed to make the oobleck dance and how to get the tone from my computer to play through the speaker (I even tried rigging a set of headphone speakers to connect the speaker directly to my laptop. It didn’t work.) After a bit of researching, I found out the oobleck moves the best with lower frequencies, around 20 hertz or so. I also found a tone I could download, burn to a disk, and play through the stereo.
I later found out the tone I burned to a disk was actually a wave; it moved up and down in frequency. As you can see in the video, the oobleck dances better at certain points in the sound than it does in others. I think the oobleck will dance better with a steady, static tone at the right frequency. That is what I will do next time I do this with the children. You can find free tone downloads here.
I set the speaker on its side and covered the speaker cone with plastic wrap. Then we were set to go! I told the students one of the best things about oobleck is that it loves to dance; but it has a funny taste in music! I poured some of the oobleck onto the plastic-wrap-covered speaker cone, turned on the tone, turned the volume up, and watched the oobleck take on a life of its own! This gave us a great opportunity to talk about sound waves and vibrations.
We noticed the oobleck moved best when the plastic wrap was tight, so I held it extra tight with my hands. It was so much fun listening to the kid’s reactions as the oobleck formed little finger-like shapes and moved around on its own! We also added some liquid watercolor to the oobleck and watched as the dancing oobleck mixed the colors together. Unfortunately, I did not get a picture of this.
Squeezing oobleck to make it solid.
After the lesson, I put the oobleck in the water table to let the kids play with and explore. I also put a few small toys in with it, so they could see how easily toys can get stuck inside. Many of the children really enjoyed getting their hands in the messy oobleck (while some preferred to use spoons to play with it), and I heard a lot of great science vocabulary coming out of their mouths as they played!
Letting oobleck drip through fingers as a liquid.
A few kids even asked for a re-play of the dancing oobleck during playtime. That is when we shot the video. By this point, the oobleck had dried out a bit, so the reaction here is not as good, but still really neat!
For more oobleck fun, check out these videos:
Running across a pool of oobleck
Kids playing in a pool of oobleck
Maybe some day we will fill a pool with oobleck! But for now, I am happy with our oobleck dancing success!
Note: Do not wash oobleck down the drain! It will settle and clog the pipes. When you are done, just scoop it up and plop it in the garbage!
Thanks for reading! Please leave any comments on your thoughts or experiences with oobleck!