Pat Riley [Lincoln Park HS] Milk of Magnesia
Pat led us in a discussion of the properties of Milk of Magnesia Mg(OH)₂, [MOM for short] and its use in treating upset stomach, heartburn, and the like.  Then she began an experiment, based upon the laboratory exercise Upset Tummy? MOM to the Rescue! A colorful Antacid Demonstration [Flynn Scientific: http://www.flinnsci.com/]. She proceeded as follows:

1. She put 20 ml of Mg(OH)₂ into a beaker and added 200-300 ml of ice to slow down any reactions, and diluted to 800 ml with water. She then turned on a stirring motor.
2. Next she added 4-5 ml of a universal pH indicator [http://www.purchon.com/chemistry/ph.htm], which turned purple.
3. She handed out color cards to use to translate the "indicator color" into pH. [pH is a quantitative measure of hydrogen ion concentration, on a negative logarithmic scale; see http://www.purchon.com/chemistry/ph.htm.]  The color of the solution indicated that the pH was around 10, showing that the Mg(OH)₂ is rather basic.
4. She then added 2-3 ml of Hydrochloric Acid (HCl), and the stirred solution turned orange, indicating a pH of about 5. Over the next minute or so the colors continued to change sequentially to yellow (pH =6) to green (pH = 7-8) to blue (pH = 9) to purple (pH = 10). We concluded that the Mg(OH)₂ was gradually neutralizing the HCl.  By the same mechanism, HCl in our stomachs is neutralized by Mg(OH)₂.
5. She added more HCl to the beaker, and the same cycle occurred.

1. Mg(OH)₂ is 5 times more soluble in hot tap water than cold tap water. In water ions are formed through the reaction Mg(OH)₂ « Mg⁺²(aq) + 2 OH^-(aq) The equilibrium constant for the reaction, determined from the concentrations, is much greater in hot than cold water.  In our experiment most of the Mg(OH)₂  does not dissolve, and thus our MOM solution looks milky.
2. The hydroxyl ions [from soluble Mg(OH)₂] and the hydrogen ions [from HCl] combine to completion in the neutralization reaction OH^-(aq) + H⁺(aq) ® H₂O(l) The color indicator thus makes a gradual transition toward the "red" end of the visible spectrum.
3. This reaction is a direct consequence of Le Chatelier's Principle:
   When stress (an excess of hydrogen ions) is applied to an equilibrium state, the reaction proceeds in the manner (direction) that will relieve the stress.
   • In our case the stress of excess H⁺ ions causes the removal of OH^- ions, and equilibrium is shifted to the right side the reaction, in order to replace the OH^- ions that are lost.
   • The net result is that more of the insoluble Mg(OH)₂ dissolved in the solution.
   • The color of the universal indicator goes back toward the violet (purple) as OH^- ions are restored.
4. The experiment can be continued many times, until all the Mg(OH)₂ has dissolved and excess OH^-(aq) is neutralized.

Marva Anyanwu [Worley-Green Elementary School, K-8] Fingerprints [handout]
One handout described the basic fingerprint patterns:  whorl, arches, loop, and composite, as shown on the website http://www.odec.ca/projects/2004/fren4j0/public_html/fingerprint_patterns.htm, whereas the other involved a study of the characteristics of fingerprints and skin, similar to the website http://safety-identification-products.com/fingerprint-information.html. Marva challenged us to explain what fingerprints have in common with tire treads.

• We began by sharing our knowledge on fingerprints. Marva asked how fingerprints can be altered. We concluded that they can be burned off and rubbed off for short periods, but that deep cuts are not effective because the fingerprints are regenerated.  Fingerprints have ridges and grooves to provide traction, just like tire treads. We also discussed the dermis -- the outer layer of skin cells that continually regenerate fingerprints as the dead cells slough off.
• We made fingerprints by inking fingers and then pressing them onto a piece of paper, as described in the second handout and website.  We all began with our left thumb, so that we could make person-to-person comparisons in a controlled way.  We also categorized our own left thumb print  into one of the four basic patterns. We found that it is not very easy to make an accurate fingerprint!
• Gary Guzdziol described a project in his school, in which one teacher submitted his/her print as that of "perpetrator", and had students  gather prints from their teachers to identify the "prime suspect".  Carl Martikean described a project involving a "mock crime", which students would solve by gathering clues such as fingerprints and other material evidence.
• We discussed the uniqueness of fingerprints, as well as foot/toe prints and other physical features.  Footprints of newborn babies are taken to establish their identity and avoid mix-ups
• We then discussed these questions:
  1. Why do your hands have so many creases on them? [for folding paper?]
  2. Explain how the calluses on a person's hand can be used to guess the person's occupation?
• Pat suggested a tie-in to genetics, to determine whether students have fingerprints that are in the same class as their parents.
• Carl  suggested that the Evidence Laboratory of the Chicago Police Department [now located next door at 35th Street and State Street] would be an excellent resource, and that somebody from there might be asked to present to a SMILE class.

Carl Martikean [Wallace HS, Gary] Teaching of Science from a Humanistic Perspective
Carl raised the following questions:

• Should animals with human gene sequences spliced into their own DNA be considered human? Why or why not?
• Why are chimpanzees immune to the HIV virus? Is it possible that there was an HIV virus among chimps, say, two million years ago, devastating the population at that time, so that only the few virus-resistant chimps survived? Why or why not?
• The crusades brought rats and the bubonic plague back to Europe from the Mediterranean basin, resulting in untold human agony and depopulation in Europe. Did this resultant depopulation serve to enhance the value of human life, leading inevitably to specialization of labor, banking and commerce, inherited wealth, leisure time, and [among those fortunate few] time and resources for scientific inquiry?  Does science drive society, or does science drive science?

Notes taken by Ben Stark.