High School Biology-Chemistry SMILE Meeting
22 February 2005
Notes Prepared by Porter Johnson

Walter Kondratko [Steinmetz HS, Chemistry] Mystery Solutions (handout)
This exercise comes via the ChemVan project sponsored by Chicago State University.

Walter came in with a number of small (25 ml) plastic squeeze bottles (most were clear, but some were brown), each containing a liquid. We started by mixing the 8 "knowns" in pair-wise combinations and noting our observations in the Table provided on the handout. We then repeated the experiment with the 8 "unknowns" and tried to infer from the patterns in the results what the unknowns might be (the "unknowns" were also our "knowns" but not labeled except by letters). Results included the following.

Formation of a precipitate. (Note the color of that precipitate) For example: AgNO₃ (soluble) + HCl ® AgCl (white precipitate) + HNO₃ (soluble))
Formation of bubbles. For example: Na₂CO₃ + 2 HCl ® H₂CO₃ + 2NaCl (soluble)
Followed by by the decomposition reaction
H₂CO₃ ® H₂O + CO₂(bubbles)

Brenda Daniel [Fuller Elementary School] Magnetism and Electricity (handout from the FOSS Science Workbook)

This activity was completed with the help of small FOSS kits. A FOSS kit is a small plastic board (about 20 cm by 25 cm). Several activities concerning electricity could be completed by inserting switches, batteries, wires, bulbs, etc. into sections preformed in the plastic board. The magnetism kit was a "baggie" with various items in it (some magnetic and some not) including a piece of magnetite -- a rock that could be picked up by a magnet (a surprise!).

Ed Scanlon asked us, "Why is it that both the North and South poles of a permanent magnet will attract a piece of iron, but the South pole of a permanent magnet will attract only the North pole of another permanent magnet, and repel its South pole?" Our discussion led to the explanation that there are microscopic magnetic domains throughout the iron, and we assumed that un-like poles attract and like poles repel. The magnetic domains are oriented every which way, so that their magnetic effects cancel out and the iron is not magnetized. Imagine such a bar of iron:

                                        __________________
                                       |                  |  
                                       |    NS-NS-SN-NS   |
                                       |    SN-SN-NS-SN   |
                                       |__________________|
                                              IRON

Now when the North pole of a permanent magnet is brought near the iron, it attracts the South poles of the domains (and repels their North poles). This makes the domains in the iron re-orient so that their South poles point toward the North pole of the permanent magnet (and their North poles are repelled away).

         _________________________         ______________
        |                         |       |              | 
        |South Pole     North Pole|       |SN-SN-SN-SN-SN|
        |South Pole     North Pole|       |SN-SN-SN-SN-SN|
        |_________________________|       |______________| 
              Permanent Magnet                 Iron
                                     (temporarily magnetized)

So the iron becomes temporarily magnetized with a South pole near the North pole of the permanent magnet. The result is an attraction between the permanent magnet and the iron. Similarly, when the South pole of a permanent magnet is brought near the iron, the domains re-orient with their North poles pointed toward the South pole of the permanent magnet, and the result is again an attraction between the permanent magnet and the iron. But that doesn't happen between two permanent magnets. The magnetic domains in a permanent magnet remain permanently oriented (or "frozen"), with their North poles pointing in one direction, and their South poles in the opposite direction. So, the North and South poles of a permanent magnet remain fixed at opposite ends of the magnet, and two permanent magnets will repel only when their like poles are near each other, and attract only when their un-like poles are near each other.

With regard to the electricity experiments, we talked about electricity in chemistry and biology.

Chemistry:
- Electroplating. For information see Electrochemistry Encyclopedia: http://electrochem.cwru.edu/ed/encycl/art-e01-electroplat.htm.
- The "warning light" in the tank of a water softener. It indicates when the water softener is no longer removing metal ions from the input stream, because the conductivity of water in the tank becomes too high.
Biology
- Electrical nerve impulses. These are rather different from ordinary electricity in wires -- for which the current is produced by the flow of electrons. Nerve impulses are produced by motion of ions, being more like waves of polarization and depolarization within the neural membranes.

Marva Anyanwu [Wendell Green Elementary School] Human Traits (handout)
We worked in pairs and investigated the first three traits in Marva's handout (eye color, "tongue rolling", and "finger crossing". Here are the results for the class:

Eye color:	9: brown	2: blue
Tongue rolling?	6: yes	5: no
Finger crossing?	5: yes	6: no

This information would allow us to infer "dominance" and "recessiveness" of the alleles for the genes responsible for each trait, particularly if our class is representative of a freely interbreeding sample of the population as a whole.

We then used a coin toss to simulate/illustrate the "segregation" of the two alleles of a particular single gene of a parent when gametes are formed ( known as Mendel's First Law), since the process is governed by simple rules of probability.

Notes prepared by Benjamin Stark.