High School Biology-chemistrySMILE Meeting
26 April 2005
Notes Prepared by Porter Johnson

Ben Stark [IIT Biology ]               Seeds of Wisdom
brought in his "seed sprouter" from the last session -- for details see Chris Etapa's  presentation from the last SMILE meeting  bc041205.html. It had been very successful, with all planted seeds apparently sprouting. There were six healthy shoots, some nearly 20 cm long with first leaves. The zip-lock bag had been open for about 10 days to permit the shoots space to grow, but the soil was still fairly moist below the surface -- although water had been added a few hours before.

Sister Mary Lucy Adetunji [Gale Elementary School]              Vinegar & Eggs
SR Mary
had tried two experiments, but they didn't work out, so she is going to repeat it for us to see if we can figure out why they didn't work  When SR Mary put a hard boiled egg into vinegar, she expected the shell to dissolve (the CaCO3 of the shell would be converted to NaCO3) and the egg to shrink (instead the egg swelled). The egg must have had a higher overall salt concentration (lower osmotic pressure) than the vinegar, and that is why it happened in this way. Soeur M also put a chicken bone into vinegar and expected the hard part (CaPO4) of the bone to dissolve (much as what happens with the egg shell) and the bone to get rubbery. But the bone stayed rigid. Probably there was not enough vinegar compared to the mass of the bone; changing to fresh vinegar or using a much larger volume of vinegar to begin with would provide enough acid equivalents to completely dissolve the CaPO4. For more details see the presentation of Chris Etapa in the SMILE writeup: bc022503.html.

Ken Schug continued with the "egg in a bottle" trick using SR Mary's hard-boiled egg. He lit a paper and then dropped it into a large Erlenmeyer flask.  Ken immediately  placed the egg in the mouth of the flask. As we watched, the egg appeared to squeeze itself slowly into the flask! How come?  A partial vacuum had been produced inside the flask. That is, room air has a greater pressure than the gas inside the flask.  The gas inside is heated by combustion, so that it expands -- some of it being expelled from the flask past the egg.  When the egg is placed on the mouth, combustion soon stops, and the air inside the flask becomes cooler. A pressure differential is thereby created, producing a net force on the egg, pushing it into the flask through the mouth. The egg can be removed from the flask by forcing air into the flask while inverting it. Again, the egg gets caught in the mouth of the flask, and the pressure inside is now greater than that outside, and the egg is forced back out.

Following instructions on handout sheets, SR Mary had us do the following activities designed for primary grade students:

  1. Balancing Act:  The sheet specified a relation between the masses of "cylinders" and "oranges" -- one cylinder has the same mass as three oranges.  She then posed balance questions  by "putting" a certain number of one object on one pan of a balance and having the students figure out how many of the other object are needed on the other pan to balance the scale.
  2. Crayon Factory:  It  provides a simple way to introduce the concept of permutations. Coloring in "boxes" of four crayons each, using 4 different colors, the children can determine how many different ways there are to order the four colors (left to right), ie, the number of permutations possible with four different items.
Well-balanced, colorful, egg popping science experiences! Thanks SR Mary.

Terri Donatello [ST Edwards School]        Rolling Uphill  + Giveaways
brought in an apparatus that seemed to show an object rolling uphill. The object is a double cone (solid wood) that rolls on a pair of wooden rails, which are pitched slightly uphill as they widen. The cone seems to move ''uphill", because it rolls "up" the rails. It does so, because as the rails widen, the center of mass of the cone actually gets lower, as more of the cone falls below the level of the rails.

Terri then showed us how the "scratch test" is used to characterize the hardness of a mineral; this is one test used to identify an unknown mineral. Also, minerals will cleave in characteristic ways (depending on the forces that hold them together). For example, mica will cleave to form flat sheets ("isinglass"; see http://www.answers.com/topic/isinglass}, that were, at one time, used for windowpanes. The shapes of their crystals also are useful characteristics of minerals; NaCl, for example, forms a nice cubic crystal.

The Cell Game! This was a board game designed to teach the parts of a living cell, which Terri described as a "real treasure". And there were lots of other treasures that Terri brought that she has used to teach almost every area of science over the years. She offered them to the class members to take with them and use in their classrooms!

Terri, thanks for everything!

Notes prepared by Benjamin Stark.