[Geysers] Geyser model

[Craig Messerman]

Our model is based on the Exploratorium versions (which all of these  
are, I guess).  I made a new one last year:  A 250 ml erlenmeyer with  
stopper and about 24 inches of glass tubing inserted in stopper.  At  
the top of the glass tubing I attached a pint-sized, clear-plastic  
container (Glad brand or some other disposable kind).  Without water  
the whole thing is light enough to stand up by itself, and it is all  
transparent to see what's happening.  To attach the little tub  
permanently I drilled the hole in the bottom by heating the glass and  
melting it through. Then I bought two small O-rings at the local  
hardware store that sit on the glass above and below the hole to seal  
it.  I used some two-part epoxy to really seal the O-rings  
permanently to the plastic and glass (plumber's putty works too, if  
you want to take it apart, but it tends to leak).   For the demo I  
use a tall ringstand to support the tub, and the flask sits on a  
small hotplate. I set it up so the top end of the tube about 3 cm  
below the rim of the tub so I can nearly fill the tub with water, get  
good splashing, and get quick recycling because the water in the tub  
stays cooler. I think the small flask also helps with quick  
recycling. We've been using this model for years and have never had  
any glass shatter. Of course, they are always Kimax or Pyrex.  I  
always fill the model with distilled water to keep it and the  
surroundings free of scale and salt.

I also model a cone type geyser very simply by putting a thick- 
walled, tall neck Florence flask (flat bottomed, 500 mL) on a  
hotplate with 50-100 mL of distilled water in it.  Heat on medium- 
high until boiling, then jam a rubber stopper in the top and crank  
the heat to full and stand back.  After a few tense minutes the  
stopper will blow off and about half the water will turn to steam,  
and with any luck the ceiling will get all wet too. I keep the whole  
thing a safe distance from my students, but I've done it 100 times  
with consistent results, always with the same flask that I hide away  
for this one purpose. I also took video of the eruptions that we  
analyze in slow motion. It's a crowd-pleaser.

Craig Messerman
Sentinel High School, Missoula, MT

cmesserman at mcps.k12.mt.us
cmflyer at bresnan.net



On Jan 14, 2008, at 12:22 PM, Jeff Cross wrote:

> I will add a few things to the posts that have been written about  
> model geysers.
>
> 1) Glass models are nice because you can see the steam bubbles  
> inside the flask.
> 2) Glass is very brittle.
> 3) Glass is most likely to break at the very end of the eruption.   
> If you have a funnel on top of the geyser, the cool water in the  
> funnel will get sucked back into the reservoir after the eruption  
> ends.  The thermal shock of this cold water on the hot reservoir  
> flask can cause the flask to shatter.  Putting boiling stones in  
> the reservoir flask will not prevent this from happening.
>
> To avoid this problem, we have used metal containers for most of  
> our models.  You can get some 2" pipe at the hardware store.  Get  
> the right pieces to make a T or L-shaped reservoir.  Get some  
> reducers and put a 4-foot long standpipe on the model, maybe 1/2 or  
> 3/8 inch diameter.  The geyser will need supports of some kind.   
> Try tying it to a ladder or something stable.
>
> Jeff Cross
> Jeff.cross at wallawalla.edu
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> Geysers mailing list
> Geysers at lists.wallawalla.edu
> 

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