Krampf
#164/165 Keeping Water in a Cup
#164/165 Keeping Water in a Cup
Krampf@aol.com
For this week's experiment, I went back to a short science show that I
developed while I was Director of Education at the museum in
Jacksonville, FL. It was a simple show, but one of my favorites. It all
centered around a simple task. Turn a glass of water upside down,
without spilling any. For this experiment, you will need:
* a drinking glass
* water
* a variety of materials from around your house
* lots of imagination
Usually, I give you specific directions to follow for the experiment,
but this week, we will try something different. Find a place where you
don't have to worry about spilling the water. I suggest working either
over a sink, in the bath tub or outside. Now, your task is simple. Put
some water in the glass and then turn it upside down, without spilling
any of the water. How can you do that? Cut a square of cardboard that
is a little bigger than the opening of the glass. A good source of
cardboard is one of the food packages that we throw away every day.
Place the cardboard over the top of the glass and carefully turn the
glass upside down. The water stays inside. You can even release the
cardboard and it will still stay on the glass, holding in the water,
held by the pressure of the air outside the glass. Simple, right?
But we are not through. Now comes the challenge. I have shown you one
way to complete your task, and for many people, this is where they
stop. As they try to solve a problem, they find an answer and then
think they are finished. Couldn't there be more than one answer? Maybe
one of the others is better. What I want you to do is to find as many
different ways as you can to keep the water inside the upside down
glass. Just off the top of my head, I came up with 8 different ways to
accomplish the task. I am sure there are many more. How many can you
think of?
Part 2
Happy Easter to those of you that celebrate the holiday. I have
actually had two glorious days at home to catch my breath. Today we
head towards Buffalo, New York for a week of shows at the Buffalo
Museum of Science. It is one of my favorite natural history museums and
I always look forward to my visits.
I was already considering sending out some of the different
possibilities for keeping water in the cup, but the overwhelming number
of e-mails that I got asking, begging and demanding to know what they
were let me know that I had focus on them this week. Let me see......I
said that I could think of four ways, right?.........Eight?.........Did
I say eight?.........Well, if I said eight, then I had better list
eight.
1. Use a solid cover to hold the water inside the glass. The one we did
last week.
2. Freeze the water.
3. Solidify it chemically. You can do this with a chemical like sodium
polyacrylate, which is found in disposable diapers. You could also do
it by adding gelatin to the water. Just follow the directions on the
package.
4. Soak the water up in something. This is one that was so simple that
it took someone in the audience of my show to think of it. Simply stuff
some paper towels into the glass. This soaks up the water and holds it
in.
5. Put it under water. When you have the glass under the surface of the
water, it will be filled. You can then turn it upside down and it will
still be full.
6. This is my favorite. Go outside. Trust me on this, as this way takes
some practice and can make a mess. Put some water into the glass. Use a
plastic or paper cup, not something made of glass. Hold it firmly at
the top. Now, quickly swing your arm in a circle, going up over your
head and then back to your side. At the top of the circle, the cup will
be upside down, but the water will stay inside. Due to inertia, when
you get the water moving, it tries to continue in a straight line. This
forces the water towards the bottom of the cup, keeping it in, even
when it is upside down.
7. Surface tension. Cover the top of the glass with some fine mesh
window screen. Rub the screen with a little oil. Now pour water into
the glass through the screen. It goes in just fine. Then place your
hand over the screen to hold the water in while you turn it upside down
(over the sink). When you remove your hand, the water stays in. The
surface tension of the water holds it together. The combination of
surface tension and air pressure keeps the water inside the cup.
8. Take it into orbit. In the microgravity of space (No, things are not
weightless in space.), you would be able to turn the glass upside down
and the water would stay in the glass.
Did you think of any ways that I missed? I am sure that there are more.
Now that you have the idea, I am certain that some of you will put your
brains to work and come up with more ways to accomplish the task. If
you do think of other ways, please let me know.
I know that I have glossed over a lot of the science, but if you want
to know more, you have a good start. A quick trip to the library or
hitting your favorite Internet search engine will yield an incredible
amount of information for you.