Handwashing potato demonstration

[uthoff <uthoff@fyiowa.infi.net>]

Someone asked for these directions several weeks back. It has taken me
this long to locate them and then I lost her email address. Sorry.
Subject:
        handwashing
   Date:
        Wed, 01 Mar 2000 10:02:44 -0600
   From:
        Susan Uthoff <x1uthoff@exnet.iastate.edu>
     To:
        uthoff@fyiowa.infi.net




2 potatoes or hands, washed in advance
(nut not by the person cutting the apple or potato)
Potato peeler
small, clean knife
cutting board
 2 sterilized jars (wipe clean with rubbing alcohol or wash in the
dishwasher)
Masking tape or gummed labels
felt-tip markers

Label the jars:
Jar 1 - Washed hands
Jar 2 - Unwashed hands

Choose a class volunteer to perform the experiment. Make sure his/her
hands haven't been washed in several hours.

Procedure
1. Without washing hands, peel one apple or potato and cut it in half on
the cutting board.
2. Place one half of the apple or potato in the jar labeled "Unwashed
Hands." Screw the lid on tightly, compost the remaining
apple or potato.
3. Wash your hands thoroughly with soap and warm water for 20 seconds.
Now wash the potato peeler, knife and cutting
board with soap and warm water.
4. Peel the second apple or potato and cut it in half.
5. Place one half of the apple or potato in jar labeled "Washed Hands."
Screw the lid on tightly and compost the remaining
apple or potato.
6. Place jars in a warm place.
7. Observe the jars once daily for a week and record your observations.

After one week, the apple in the "Hands Unwashed" jar should show signs
of microorganism growing. The
microorganism grew because it was transferred to the apple by dirty
hands. The apple in the "Hands Washed" jar
should appear relatively free of visible microorganism growth.

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