Summer time is great for focusing on the fun part of learning. Every Wednesday this summer, we will be doing small but fun activities and experiments with the children to bolster the idea that learning does not have to be a bore. Included in the activities will be competitions, group experiences, and even some low level engineering challenges.
Most recently, we decided to start with something easy to make at home. Oobleck. Named after the Dr. Seuss story “Bartholomew and the Oobleck”, it is a simple mixture of 1 part water to roughly 2 parts cornstarch. Easy to put together, fun to play with, and quite possibly a mess, so if you plan to do this at home, make sure you either get a nice disposable table cloth or take the kids outside.
We start the discussion with all the ingredients on the table. This will be a discussion of states of matter and some of their properties, but the kids don’t know that. I ask them what I poured into the measuring cup. Most say “water”. I ask “what is water”? After some thinking, they decide it is a liquid. They tell me it is wet, and that it “moves around a lot” (inside the cup).
I then point at the table. I knock on it. I ask “if water is a liquid, what is the table? Again, a pause for them to think, but one child quickly decides it is a solid. They tell me it is “hard”, and it “does not move around” like the liquids. Fair enough. With the range of ages in this group (5-12) I don’t want to get super bogged down in the details, but we have basically started learning about states of matter.
I ask them if it is possible for something to be both solid and liquid. They are not sure. Lots of “no”, a few “yes”. I tell them that sometimes there are substances that can act like both, and that we are going to make one. I ask them if they have ever read the book “Bartholomew and the Oobleck”, by Dr. Seuss. I show them a picture of the cover, and one child says he has it at home. I recommend they read the book but ask if they want to see Oobleck this afternoon, and I get a loud “YES” in unison. Time to “cook”.
I take a white 2-gallon bucket I bought at Walmart and pour 2 cans of corn starch in the bucket. I ask them what would happen if we took the table and ground it up? They say it would be sawdust. One says powder. I agree and tell the that powders are also solids. Just broken up. While they think about that, I grab the water and start mixing the 2 ingredients. As I pour and mix, a change begins to happen. Curiosity gets to the kids, and they start to stand and peek into the bucket as I churn the mixture.
Eventually I get the right level of mixture, which makes mixing harder. The Oobleck thickens as pressure is applied, so moving the spoon has now become difficult. I add a little more water, and slowly lift the spoon. A slimy white substance drips down into the bucket. The children stare wide-eyed at our creation.
I ask them what came off the spoon, solid or liquid? They said it looked like a liquid (of course one comparison was to mucus). I asked what they thought would happen if I hit the Oobleck? Some said my hand would get wet. Some that it would splash our of the bucket. Once thought it would act like rubber and my hand would “bounce out of the bucket”.
I punch the mixture, and it hardens, preventing my hand from going in. I lift out my hand, covered only by a small amount of Oobleck. I ask them to stand up, and I lean the bucket over. The Oobleck moves like water towards the edge of the container. I tap it and it hardens. Then the real fun begins. Each child gets to come up and test the Oobleck both ways (slow/soft touch verses fast/hard). If you do this (and you should), be prepared for that one kid that sticks their arm in slowly as far as possible. Fun messes will be made.
We wrap by talking about liquids and solids again. I share with them the simple version of how Oobleck acts as both, that the powder in the water gets closer when the Oobleck is hit by pressure (pushing, hitting, running), and that is what makes it hard. One child says it sounds like quicksand. I agree. And just like quicksand, you can move across it quickly without sinking in, or you can get out of it by moving slowly.
I then add food coloring to the mixture and double bag the Oobleck to go home. I show the kids how to make it behave without taking it out of the bag. Hopefully they remember that at least until they get home.
I realized after we finished the activity that we did not get clear images of the kids testing the Oobleck. We will rectify that during the next experiment. 🙂
For more on Oobleck and other Non-Newtonian fluids, here is a short bit of information via Wikipedia.