Hey Science Fans!
What do you call a liquid that isn’t a liquid, at least all the time? The technical term is a non-Newtonian fluid, but a lot of people call it oobleck – in reference to the Dr Seuss book Bartholomew and the Oobleck!
Centuries ago, Sir Isaac Newton proposed that fluids should behave in a constant, predictable way – think about water. If you’re swimming, it doesn’t matter if you’re swimming fast or slow, the water will always flow around you. Liquids that behave this way are called Newtonian Fluids. However, not all fluids behave this way. We call these fluids non-Newtonian fluids, and we’re going to show you how to make some today!
You’ll need a pie plate, some cornstarch, and some water. Feel free to add some food coloring if you like.
Start with a cup of cornstarch and then slowly add water until the cornstarch is no longer grainy – you’ll probably need about ¾ of a cup, but your results may vary. As you slowly mix the cornstarch and water, you’ll *think* you’re creating a normal fluid – you can move your spoon freely, and even scoop it and pour it. But, if you slap the top of the dish with your hand – it’s suddenly a solid! You can even pick it up and create a ball with it in your hands, but as soon as you stop applying pressure it falls apart and runs through your fingers!
So, what’s the science here? As you apply force to the oobleck it become MORE viscous. The particles of cornstarch get jammed into each other, trapping the water molecules between them and preventing them from flowing the way they normally would. Scientists don’t ACTUALLY know all the details about why or how this works! But there is significant interest in oobleck because there are a lot of potential uses. For example, it could be used to make very comfortable body armor for first responders, or even a fast, temporary filling for potholes!
Cornstarch and water aren’t the only non-Newtonian fluids, or even the most famous. In fact, if you’ve ever eaten French fries, you probably know about another - ketchup! Ketchup is also a non-Newtonian fluid – but instead of getting thicker under pressure like the cornstarch mixture does, ketchup gets thinner! That’s why it’s easier to get ketchup out of a plastic squeeze bottle than it is to get it out of a glass bottle.
Try this demonstration for yourself - and share your results below!
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