Download Oobleck Explained - Otterbein Neutrino Research Group

Oobleck Explained
When you punch the cornstarch quicksand, you force the long starch
molecules closer together. The impact of this force traps the water between
the starch chains to form a semi-rigid structure. When the pressure is
released, the cornstarch flows again.
Another explanation
So why does this concoction act the way it does? Most of it has to do with
pressure. The size, shape, and makeup of the cornstarch grains causes the
cornstarch to “lock-up” and hold its shape when pressure is applied to it.
People have filled small pools with oobleck and they are able to walk across
the surface of it (as long as they move quickly.) As soon as they stop walking,
they begin to sink.
And still another (probably the best)
The cornstarch is made up of long chains of atoms - a polymer. These chains
can move past each other, but they take some time to do this. If you pour it
slowly, it can flow like a liquid. If you try to force things and make the
chains slide more quickly than they want to, they get entangled - and the
mixture gets firmer. So if you push hard on it, it acts more like a solid.
The real explanation is actually a bit more complicated than this. But the
exact workings of mixtures like this is something that is not all that well
understood. Folks sometimes get upset when there is no really good answer
for things in science, but really that's a good thing - if we already knew
everything there was to know, there would be no reason to try new things and what's the fun in that?
Another good one:
Middle/High School Level:
What caused the oobleck to act like a solid or like a liquid? Pressure. When
enough pressure was applied, the oobleck acts like a solid. When little or no
pressure is applied, it acts like a liquid. Why do you think oobleck acts like
this? What size are polymers in the world of atoms and molecules? Polymers
are very long chains. How might that influence the behavior of oobleck?
When pressure is quickly or heavily applied the chains have less time to move
and get tangled up. When little pressure is applied, the chains have time to
slide past each other.
Adding the cornstarch to the water changed the reaction time of the liquid.
Usually liquids move so quickly we do not notice how long it takes them to
move. Oobleck has a finite reaction time. We can see how long it takes for it
to react. We can make oobleck act like both a solid and a liquid. A liquid like
this is called a non-Newtonian fluid because it does not follow the rules that
Newton discovered most liquids follow. A non-Newtonian fluid has properties
of both a solid and a liquid and reacts to stress with increased viscosity. Can
you think of other non-Newtonian fluids? Quicksand is one example. How do
you think you should you move in quicksand?
Adding any polymer to a liquid will increase its reaction time. However,
different polymers will increase the reaction time different amounts. Most
of the time, we will still not be able to tell the reaction time changed
because it will still be very fast. We do not know why cornstarch increase
the reaction time so much. Cornstarch is often appears as a special polymer.
This is an area that you could research as you learn more science.
Was the creation of oobleck a physical or chemical reaction? It was a
physical change. Cornstarch (amylose) and water can be considered a
colloidal suspension. A colloidal suspension is a two-phase system in which the
starch and water are not dissolved but simply mixed into a permanent
suspension that will not settle on standing. Other examples of colloids are
blood, fog, whipped cream, foams, Jell-O®, and styling gel.