One afternoon, the Free-Ride offspring were in the mood for some spur of the moment experimentation.
So, we cleared the kitchen table, rummaged through the cupboards, and came up with a plan.
The question we decided to investigate:
What happens to different dry ingredients when you add water to them?
We put each of the dry ingredients in its own little bowl. (If they got mixed up, that would make it harder to figure out what was going on.) Also, to help us remember what was in each bowl, we labeled the wooden sticks that we used to stir once the water was added.
The dry ingredients we used were matzo meal, all purpose flour, whole wheat flour, soy flour, baking soda, salt, cocoa powder, and corn starch. We pretty much went with what we could find in the cupboards, but I made a point of finding the salt, the baking soda, and the corn starch.
We used tap water, and didn’t measure it at all precisely. Our main goal was to get each dry ingredient really wet without overflowing the bowls they were in.
The sprogs started with the table salt. When they added water and stirred, “the amount of salt is less,” says the younger offspring.
“It’s not actually disappearing,” remarked the elder offspring. “It’s dissolving in the water.”
Stirring made more of the salt disappear, although we didn’t get to a completely clear solution. Probably this means we had an excess of salt for the amount of water we could fit in the bowl without spilling, at least at room temperature. (Actually, “room temperature” when we did this was about 85 oF.)
The stuff that looked like water tasted salty, more evidence that the salt hadn’t been zapped into oblivion.
The baking soda also dissolved in water (although the taste of the resulting solution was pronounced “really bad” by both sprogs). Unlike the salt, however, the baking soda bubbled a little as we stirred the water in.
“You can make a volcano with baking soda and vinegar,” noted the elder offspring.
“Do the bubbles mean that water is kind of like vinegar?” asked the younger offspring.
We then moved on to the floury ingredients.
Add the water was added, the all purpose flour started out sort of lumpy. With more stirring, though, the lumps went away.
“The flour’s not going away like the salt did,” observed the younger offspring.
“No, it’s getting to be like a paste,” replied the elder offspring.
“Do you know that when I was I kid we used to make paste from flour and water?” I asked.
The sprogs rolled their eyes.
Adding water to the whole wheat flour made a paste with a slightly grittier texture. (More fiber!)
Adding water to the cocoa produced a cocoa colored paste.
“It looks like chocolate sauce!” cried the younger offspring.
It did not taste like chocolate sauce. (Doing experiments in which all of the ingredients are safe to taste ensures safety, but not deliciousness.)
By the time we got to the soy flour, we expected that it would make a paste rather than dissolving. And it did, but it surprised up by making bubbles.
“The baking soda did that, too,” said the elder offspring, “but the soy flour doesn’t taste anything like the baking soda.”
We’re not entirely sure where the bubbles came from, but we may be mixing soy flour with vinegar at some later date, just to see what happens.
The matzo meal didn’t really make a paste so much as a porridge-like substance. The younger offspring pronounced it tasty.
Finally, we got to the corn starch.
We added the water gradually with vigorous stirring. In fact, at first we overshot and added too much water, which gave us a cloudy white liquid. So, we added more cornstarch and stirred some more.
At which point we achieved oobleck!
We did not go into a long discussion of the theoretical basis for non-Newtonian fluids. Rather, we squished around in it to see how it behaved.
“I love this!” squealed the younger offspring. “If you squeeze it hard you can pick it up like a snowball, but if you stop squeezing, it melts back into the bowl.” The younger offspring spent a good half hour in the oobleck, moving fast and moving slowly, poking gently and pushing hard.
I did not show either of the sprogs this video. We don’t have a pool, and we’re not planning to get one. (Nor are we going to fill our bathtub with oobleck, thank you very much.)
A few days later, we tried to make oobleck with potato starch. It worked just as well as corn starch, but, according to the younger offspring, tastes better.