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I have a different hypothesis, more "out there", but much like the
Jeff's. Perhaps the paper mache' glue (water and flour?) is somewhat
exothermic while "curing." (or, it warms up to room temperature after
the water evaporates?). This may have been enough to make both balloons
expand for a few hours. The most likely place for a paper-mache'-covered
balloon to expand would be at the narrow, tied-off end (which would
subsequently separate itself from the mache somewhat).
So, after hours, the upside down balloon wouldn't do much: expand up,
then collapse back to normal as it cooled. The nozzle-down balloon,
though: it would displace air in the cup as it expanded, but upon
cooling would find itself sealed within the cup as it tried to contract
back to its normal shape.
This eliminates my concerns about how fast the air in the balloon cools
versus the air in the room versus air in the cup. But it's completely
hooey if paper mache' doesn't heat up (much) while curing.
That said, Jeff's got a great point: the air in the cup would
undoubtedly cool at a slower rate than the air outside, so the
egg-sucked-into-a-bottle analogy seems very feasible. In either case,
the shape of the cup very likely creates a very good seal, since it's so
similar to the tapering of a balloon at the nozzle.
If I were a betting man, I'd go with Jeff's idea, though.
Shane Pickett
-----Original Message-----
From: Informal Science Education Network
[mailto:[log in to unmask]] On Behalf Of Jeff Rosenblatt
Sent: Wednesday, February 21, 2007 1:04 PM
To: [log in to unmask]
Subject: Re: balloons gone mad
ISEN-ASTC-L is a service of the Association of Science-Technology
Centers Incorporated, a worldwide network of science museums and related
institutions.
************************************************************************
*****
Alissa,
What a nice little experiment your educator discovered.
From your description of the set up, here is my guess.
What happened to the balloon has everything to do with air pressure.
You said the water in the cups was at room temperature, probably around
70 degrees F, or so. Then the little portion of air between the water
in the cup and balloon was also probably 70 degrees too.
Overnight, if the temperature in the room went down to 60 degrees F
(which most people do to save money), then the air and the water also
decreased to 60 F.
This temperature change caused an overall decrease in air pressure, or
lower air pressure, in the cup. So the air pressure around the cup then
becomes higher, and the higher air pressure always moves towards lower
air pressure in the cup. The only thing in the way of the higher air
pressure moving is the balloon, so the higher air pressure pushes the
balloon into the cup.
That's it. It's just like the well-known egg getting 'sucked' into an
Erlenmeyer flask which has hot air turn to cold air, and so it creates
an air pressure difference.
I'm going to have to try this one out. Hope that helps.
Jeff Rosenblatt
Education Manager for Physical Sciences
Science City at Union Station
phone: 816-460-2218
email: [log in to unmask]
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-----Original Message-----
From: Informal Science Education Network
[mailto:[log in to unmask]] On Behalf Of Daniels, Alissa
Sent: Wednesday, February 21, 2007 11:06 AM
To: [log in to unmask]
Subject: balloons gone mad
ISEN-ASTC-L is a service of the Association of Science-Technology
Centers Incorporated, a worldwide network of science museums and related
institutions.
************************************************************************
*****
OK, my scienctific friends, wrap your heads around this little
accidental experiment.
One of our art educators is creating models of hot air balloons. He
covered two regular latex balloons in papier mache. He set them both on
plastic cups to dry. The cups were filled about half way with room
temperature water. He placed one balloon with the narrower, tied end in
the cup, and placed the other with the opposite (wider) end down on the
cup.
This morning, the second balloon had dried just fine. The first balloon
(with the knot end down) had something a little unexpected. The balloon
had come loose from the surrounding papier mache and had been "sucked
down" into the cup. The balloon is still inflated and tied, the cup is
quite tight around it, and the top part of it is still inside the
hardened papier mache.
So what happened? I feel like it has something to do with air pressure
but I'm not sure what. Stretch those brains and help us solve this
little mystery.
thanks!
AD
~~~~~~~~~~~~~~~~~~~~~~~~~~
Alissa Daniels, Science Program Manager
Boston Children's Museum
617-426-6500 x342
www.BostonChildrensMuseum.org
The most exciting phrase to hear in science, the one that heralds new
discoveries, is not "Eureka!" (I found it!) but "That's funny..."
--Isaac Asimov
~~~~~~~~~~~~~~~~~~~~~~~~~~
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