Hi everyone and welcome back!
Today we started off with a refresher about atoms and molecules. Individual atoms combined into larger molecules can display very different traits. To illustrate this, we made glucose molecules, which are composed of hydrogen, oxygen, and carbon. Despite being made of life-giving oxygen, you can't breathe it, just like you can't breath water despite it containing oxygen. And glucose molecules are the component parts of starches, which taste extremely bland.
Starch is a good source of energy, however, because it can be turned into sugar. In our mouths, we produce enzymes in our saliva that begin to break it apart into those sugars, so that if you hold something starchy in your mouth, it will begin to taste sweeter. It's believed this adaptation helped our ancestors know to eat starchy foods. We tried it out with corn starch and, although it's not very sweet compared to modern day candies we make out of pure sugar, it's still possible to taste the change.
Then we made oobleck by adding water to the cornstarch. Oobleck does not form a new molecule when the two ingredients are combined and can actually be separated very easily - simply squeezing it hard enough, as the kids tried, will push the water out again and turn it into damp corn starch. The resulting substance does have some very unusual properties, though, due to its ability to shift rapidly between solid and liquid depending on pressure. My favorite is that you can cause the fluid to tear if you try to make ripples the way you would in water.
If your kids want more time to play with it, it's very easy to make at home. Just pour some cornstarch into a bowl and add a bit of water until it has the right consistency - your kids should be able to tell you when it's right!
Next week, we'll talk about exactly why oobleck has these properties and then make gak, a compound.
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