In this science experiment we will make Oobleck and Glurch while learning about Solids and Liquids.
A great way to teach early grade schoolers about solids and liquids is with Oobleck and Glurch.
Oobleck is a Non-Neutonian fluid. This means that when a small amount of force is used, it acts like
a liquid, but when more force is applied, it acts like a solid. For instance, one can slowly put a spoon
in Oobleck, but it is impossible to stir it quickly. Another fun activity (though potentially messy!) is to
pour a little Oobleck in the palm of your hand and watch it puddle like a liquid. Now make a fist and
quickly open your hand. The Oobleck will have formed a hard ball from the pressure of your fist; but
when the pressure is release, it will seem to "melt" into a liquid again.
Materials To Make Oobleck:
- 1/2 quart water
- 2 boxes cornstarch
- food coloring
- Bowl and Cookie Sheet
Watch The Non-Newtonian Oobleck Fluid Experiment Video:
Describe solids and liquids.
Though most children can name a dozen solids or liquids, they usually don't know about the
molecular differences. I find that it is easy to explain with a model. Cheerios work great for liquids --
they roll around, take the shape of the container and aren't bound to one another. Several Legos stuck
together are the perfect solid -- they alway keep their shape, are hard to the touch, and stick together. I
try to use the models only after a student has named a bunch of solids and liquids. Problems you
might encounter include sand and pillows. It is difficult to explain why these are solids and not
liquids, so be creative!
What can we do to tell them apart?
What is something that is different in every solid and every liquid and how they could test that. They
should come up with the following for tests.
1. push test -- can you push into it?
2. pick up test -- if you pick some up, does it all come up?
3. pour test -- does it pour out smoothly, or does it just fall out in a clump?
4. shape test -- does it keep the same shape?
Make a chart of these rules so that they can test any new materials by seeing if they match.
Process for Making Non-Newtonian Fluid Oobleck:
Put the water and food coloring in a large bowl and begin adding the corn starch and mixing.
Eventually the mixture will get thicker; keep adding and stirring. You will know when you have Oobleck!
It will be about the same consistency as honey.
The Science Behind Making Oobleck
The mixture is a non-newtonian fluid. That means it acts like both a solid and liquid. When you pick
up a handful and squeeze it, the pressure makes the substance act like a solid for a fraction of a
second. However, as you stop squeezing and release the pressure it flows away like a liquid. When
you slap or punch a non-newtonian fluid it acts like a solid and does not splash. If you slapped a bowl
of water (liquid) it would splash all over the place! Oobleck is a good example of quicksand. Put your
hand on top and it feels solid for a few seconds, then your hand slowly begins to sink in like a liquid.
Materials To Make Glurch:
Glurch is a polymer that the children can actually watch polymerize. By mixing two liquids together and
stirring, a sticky, gooey ball will form; this is Glurch. Because the newly formed Glurch has water
trapped in its polymer matrix, it also exhibits a lot of the characteristics of solids and liquids. Though it
seems solid, it will actually "pour" very slowly and it will take the shape of its container. Yet it sticks
together and can all be picked up at once.
There are actually two solutions for Glurch. The first is 50% water, 50% white glue and food coloring.
The second is a nearly saturated solution of sodium borate (I would experiment to see how much you
actually need. I usually just dump a couple tablespoons in a half quart and shake.) Give the students
equal volumes of the two solutions to mix.
The Science Behind Making Glurch
Is it a solid or a liquid? Again, it has properties of both. This is because there is still water stuck in the
polymer matrix; dried Glurch acts very differently. The best model for Gluch I have found is one of
those magnet-art toys that have a magnetic base and numerous small metal pieces that can be
shaped any which way.
Make sure that the students understand that in science, things aren't always what you expect (mix two
liquids and get a polymer) and that not everything falls into neat categories (non-neutonian fluid).
Often there is a child that wants to know what will happen if they mix Oobleck and Glurch. Though this
results in a compound that is not as interesting as either alone, that type of inquistivness is
wonderful. Now get some friends together and make some Oobleck and Glurch!
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