High School Biology-Chemistry SMILE Meeting
28 January 2003
Notes Prepared by Porter Johnson
Roy Coleman made a presentation before the group--- in the spirit of Popeil-GinsuŽ Knife Commercials. Using an electronic projector and laptop computer, he showed us samples of the content of a CD containing all information on the SMILE and SMART websites.  But, wait; there was more stuff on it! All for just $10! And on a CD nicely packaged in a beautifully labeled jewel case.

Then in a short ceremony of sorts, Roy also presented several long-term staff members with cups bearing  the inscription: Where's My CoffeeŽ  [Magic Coffee Happy Face Mug; Item No: 4706; ordered from The Johnson Smith Company  ([http://www.johnsonsmith.com/]. There are dark, frowning faces on the cup when it is empty, and bright, smiling faces when the cup contains HOT coffee. Roy showed that it was important to keep it filled with HOT coffee, since the change is thermally activated. What a wonderful eye-opener! Thanks, Roy!

Pat Riley [Lincoln Park HS, Chemistry]      How Thick is a Piece of Aluminum Foil??
had us separate into groups of about 4, and then gave each group the following problem:

Task: Determine the thickness of Aluminum foil!  Write down the steps your team does in order to solve this problem.

Time:  You have 20 minutes to solve the problem

There is more than one way to attack this problem. The following solutions were proposed:
  1. Fold the foil over a number of times [and count how many times!], press the folds flat so that there is no space between them, measure the total thickness, and divide by the number of folds.
  2. Cut a piece of foil, and measure its surface area and its mass M . Then, fold it up, put it in the graduated cylinder partially filled with water, and measure the volume V displaced by  the compressed foil. Now, the density, D, of Aluminum foil of mass M, volume V, area A, and thickness t are related by
    D = M / V = M / ( A t)
    Solve to determine the foil thickness t.
  3. Proceed as in the previous case, but use the density of Aluminum given in the textbook (say, 2.699 g/cm3 at 20° C), which would surely be more accurate than that determined in the rather difficult, imprecise measurement of D in the previous step.
  4. ... and ... Did anybody  who read the label on the foil box  make use of the information given there?  Was this just 3 mil foil, [thickness t = 0.075 cm] or what?

Good work, Pat!

Therese Donatello [St Edwards Elementary School]      The Nuts and Bolts of Chemical Compounds 
Therese helped us understand chemical ions at a molecular level by using various types nuts and bolts to model them.  We divided into groups of about 4, and she gave each group a set consisting of 4 nuts and four  bolts. The nuts and bolts all had the same diameter, but the bolts were of various lengths.  The length of a bolt represents its "valence", corresponding to the maximum number of nuts that would fit on the bolt. A bolt of "valence two" will hold two nuts, etc.  There were various types of nuts, with square heads [Sq] or hexagonal heads [Hx].  We could use the symbol [Bo] to represent a short bolt, as well as [Bl] to represent a long bolt.  Then, the configuration with two hexagonal nuts on a short bolt is represented by the symbol [BoHx2], whereas with two square nuts it would be [BoSq2].

We could also "combine" the bolts by having two short bolts to share the same hexagonal nut. This would correspond to the combination [Bo2Hx], in our symbolic notation. We could then use bolt combinations  to model chemical reactions.  For example, the reaction [combination]

2 long bolts + 2 hex nuts ® 2-2 structure
could be represented symbolically as
2 Bl + 2 Hx ® Bl2 Hx2
Note that, as an example, the "compound" Bo2Sq2 is represented by two short bolts attached with two square nuts, and similarly for other configurations. We are limited as to what configurations we can make with the types of bolts and nuts in question, and that reflects an intrinsic property of the corresponding chemical compounds.

A nutty but good idea, Therese!

Notes taken by Ben Stark.