This week, the Sisters at Reavis made oobleck!
First, the girls talked about whether they thought there were essentially two different kinds of people in the world (like cat people vs. dog people). The consensus they came up with was: No! People are essentially the same, and there’s no need to divide them up.
Great! Now, on to our lesson: As it turns out, there are two different kinds of fluids in the world. There are Newtonian fluids, which have a single density and can’t be compressed. Most fluids that we think of, like water, are Newtonian–if you put your finger in a cup of water to push it down, the water doesn’t push back; it just moves out of the way. On the other hand, oobleck is a non-Newtonian fluid–its density can change, and it can be compressed like a solid. Let’s see it in action!
Oobleck is made by mixing cornstarch and water (adding just a few drops of food dye for color). We mixed it up in a large bowl and tried to get the proportions just right. The Sisters got messy–cornstarch and water everywhere! But finally, we got it!
Experiment time: What happens when you hold oobleck in your hands? Now, what happens if you roll it up, or if you push on it?
The answer is very surprising! When you hold oobleck without putting force on it, it flows through your hands like a liquid; but when you push on it or roll it between your hands, it hardens and acts like a solid!
Each Sister scooped some oobleck into a ziploc bag and began experimenting in various ways: Alita added some more cornstarch to see what would happen, and Aaliyah started throwing it against the ceiling to see if it would harden on impact. Then, they each took their oobleck home to do further experiments–Kemonte wanted to put the bag in her freezer to see if the water and cornstarch would separate and freeze. We’ll catch up with the results next week in Sisters4Science at Reavis!