Wanda Pitts [Douglas Elementary School]      Balancing Act
Wanda began by showing us an apparently unopened pop can that balanced on the table when tilted on its edge, as indicated below:

Wanda next handed out an arch shape, an isosceles triangle shape, both cut from the same heavy paper stock, and two clothespins.  We were challenged to balance the arch on the apex of the triangle, with the apex pointing up.  This was difficult but possible.  We then hooked the clothespins on the left and right corners of the bottom of  the triangle, and balanced the triangle by placing our finger at the center on its bottom.  Then, we gently put the arch on the apex of triangle. It turned out to be rather easy to balance the triangle-clothespin combination on a finger, since we used the same principle as the balance bar employed by tightrope walkers.

We continued with a general discussion of how to use the center of gravity to aid in balancing objects.  Ken Schug continued Wanda's miniteach with materials from his bag of tricks!

Great job, Wanda!

Chris Clausing [Bloom Trail HS]      CD Spectroscope [handout]
Chris made a CD spectroscope using the same procedure as that described by Kathy Hocker in the Math-Physics section today.  We looked at various light sources in the room using the spectroscopes that she had made.  Here is some information from her handout sheet:

"A spectroscope is a device that separates light into its component colors.  The way a spectroscope does this is to make use of something called a diffraction grating.  Light reflects and refracts through this diffraction grating, and the different colors of the spectrum all refract a little differently.  This is how the colors are separated into the colors of the rainbow.  A CD contains a large amount of information encoded onto its surface.  This information is stored in concentric rings so that it can be read by a laser beam while the disk is spinning.  These concentric rings can act as a diffraction grating if the light hits them just right. Around the room are 6 different light sources.  Each of the light sources corresponds to a different element.  Your task will be to identify the elements, based on their line-emissions."

Each light source would be expected to have a different emission pattern, since that is dependent on the nature or the source, the energy levels for electronic transitions, etc.

Interesting stuff, Chris!

Ana Timbers [Haven Middle School, Evanston]      Starch in Green Leaves
Ana had a beautiful, large, hand-lettered and hand-drawn poster, which she posted on the blackboard in the front of the class, to help us follow these instructions:

1. Remove two leaves from a healthy plant that has been growing in a sunny spot.
2. Remove the green color from the leaves by heating water in a large beaker until it boils.  Turn off the heat source, move the large beaker off the heat source, place the leaves in a smaller beaker, and cover the leaves with methanol. [Be careful! Methanol is poisonous and highly flammable!] 
3. Put the small beaker into the large beaker containing hot water.  The methanol will become warm enough to boil.
4. Soak the leaves in the warm methanol for 5 - 10 minutes.  The methanol could become green as it dissolves the coloring of the leaves.  Simultaneously, the leaves should become pale.
5. Remove the leaves from the methanol and rinse them in tap water and spread them face up on a piece of white paper.
6. Treat one leaf with three or four drops of a tincture of  iodine solution.  Then place the leaf in water to fix the color --- to make it permanent.  Compare the treated leaf with the untreated leaf.  Look for any slight change in color.

Why does the iodine produce the color change in the leaf?  [Actually, it was too difficult to see any color change because the iodine solution too concentrated and would cause a dark stain, even with out starch present..  Therese suggested diluting the iodine solution with isopropyl alcohol. Then the iodine had a golden color --- easily distinguishable by that black color made in the presence of starch.]  We concluded that the iodine had reacted with the starch in the leaf, which remained there even though the chlorophyll had been removed previously.  To demonstrate the starch reaction more vividly, Marva Anyanwu suggested we put iodine on a piece of bread --- and that turned out to produce a very striking color change.  

We experienced the Biology of everyday life!  Thanks, Ana!

Brenda Daniel [Fuller Elementary School] and Erma Lee [Williams Elementary School]      Different Salads in a Bowl
Erma and Brenda made a salad consisting of various mystery ingredients, which we identified and categorized according to the organism, and part of organism, that was the source of each:

April 08: Carol Giles