Saturday, October 29, 2011

The “Mini Grain Elevator” Demo

Take a look at this one!

I have wanted to do this demo ever since my second year of teaching.  I have read the instructions many times, found in Volume 1, Demo 1.41 of Shakhashiri’s Chemical Demonstrations.  Every time I have read them, I would think, “I’ve got to try this, but it seems scary.”  The set-up always gave me pause.   I put it off until I “had more time”; just another excuse to delay plunging into this experiment.

The Flinn Kit
At the end of last year I was looking through the Flinn catalog for my summer supply order.  The kit for the Mini Grain Elevator caught my eye.  I decided to get the kit and give it a try; surely a kit would be easier and the experts at Flinn have tested it.   I was still too scared to do it by myself, so I dragged my ever-willing colleague into the fun.  We set up the quart sized paint can with a pipette full of lycopodium powder. Just light the candle, secure the lid of the can with a hammer, and then squeeze the pipette into the sealed paint can.  Simple, right?  The instructions for the kit say, “Stand back as far as possible as you squeeze the pipette.”  This didn’t put us at ease. On the first try we got a big bang, the lid flew off, it was exciting.  But the pipette rig was not reproducible.  Attempts two and three were duds, nothing happened and the candle went out.  I decided to go back to “the bible” and, with the support and enthusiasm of my colleague, together we spent the afternoon building our Mini Grain elevator rig.

Here are a few pictures from the construction of our Mini Grain Elevator.   We bent a funnel for the inside of the can, punched a hole in the paint can, scrounged around the science building for a rubber bulb, and put the whole thing together in a 1 gallon paint can.

This rig was awesome.  It made a loud explosion, the lid flew off the can, flames shot out of the top of the can, and the candle flew out of the can.  Attempts two and three were equally impressive.  Making the rig was worth the effort! My colleague and I spent a couple of days setting off the Mini Grain Elevator for all of our classes and for any other visitors to the lab.   It was really fun every time we ignited the can.  The physics guys next door and the biology teacher down the hall came in to watch it go off several times too!  My husband even made the trek from the next building to watch the famous Mini Grain Elevator explode.  My reputation as a closet pyro was confirmed with this demo.
Bending the stem of the funnel.
Second attempt.  We broke the first funnel.

I used my awl to make a hole in the paint can.
A look at the inside of the can.

Attaching the funnel to the can.
Loading the lycopodium powder.

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