Oobleck and Glurch
Oobleck and Glurch --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.
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.
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.
Oobleck:
I would recommend making about a quart for 25-30 students, but the amount really
doesn't matter.
1/2 quart water
about 2 boxes cornstarch
food coloring
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!
Play with it. Make observations. This is when the children can run the four test on it
and see how it reacts. Older children could write a more detailed description.
Is it a solid or a liquid? Actually, it is both in a way. Oobleck is a non-neutonian liquid.
All that means is that it is a liquid that doesn't follow Newton's equations for liquids
under pressure. I haven't found a good model for this, but some children might have
seen glass in very old buildings that is thin at the top and thick at the bottom. That is
because glass is also a non-neutonian fluid and is slowly flowing out of the pane.
Glurch:
water
white glue
sodium borate
food coloring
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.
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.
What did we learn?
I like to 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
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.
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.
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.
Oobleck:
I would recommend making about a quart for 25-30 students, but the amount really
doesn't matter.
1/2 quart water
about 2 boxes cornstarch
food coloring
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!
Play with it. Make observations. This is when the children can run the four test on it
and see how it reacts. Older children could write a more detailed description.
Is it a solid or a liquid? Actually, it is both in a way. Oobleck is a non-neutonian liquid.
All that means is that it is a liquid that doesn't follow Newton's equations for liquids
under pressure. I haven't found a good model for this, but some children might have
seen glass in very old buildings that is thin at the top and thick at the bottom. That is
because glass is also a non-neutonian fluid and is slowly flowing out of the pane.
Glurch:
water
white glue
sodium borate
food coloring
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.
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.
What did we learn?
I like to 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
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