High School Biology-Chemistry SMILE Meeting
08 March 2005
Notes Prepared by Porter Johnson

Wanda Pitts [Douglas Elementary School]            The Straw Balance and Gravity
Wanda started out by asking the question, "What is gravity?" It is the force that pulls two objects together. We then received a handout from Wanda with the instructions for building the straw balance using the materials that Wanda supplied (ruler, drinking straw, marking pen, scissors, small index card, straight pin, and two wooden blocks of equal height and not as wide as the length of straw).  When the balance is level, both gravity and torque are at work, the gravity producing the force on each "pan" (ie, card), and the distance from the center of the straw to the pan multiplied by the force producing the torque, which balances the pans. But if the distance from center to pan is the same on each side, the balance will directly measure the force of gravity (the weight) of whatever is placed on the pans.

We then did this with small pieces of index card of unknown mass/weight on one pan, measuring their mass/weight in units of "punch holes", pieces of paper made with a paper punch, placed on the other pan. At the balance point, the masses and weights on each side were equal.

Good stuff, Wanda!

Carol Giles [Collins HS]            The Heat Treat
Carol gave us small packets [rectangular, about 4 cm ´ 7 cm ´ 0.3 cm] with a paper-like covering, which are called "Heat Treats" (http://www.warmers.com). These are commercially available, very portable hand and foot warmers. Carol asked us to guess what was going on with the packets to make them work as warmers, but without opening the packet. The packets seemed to have a powder inside. When we crumpled a packet to mix the contents, or just held a packet tightly in our hands, the packet got warm.

Pat: We started an exothermic chemical reaction involving the contents of the packet. Perhaps the crumpling or just holding the packet in the hand provided enough activation energy to start the reaction. The website didn't have any information on what the chemicals were, so we opened a pouch. It was full of a blackish powder that almost had the consistency of potting soil. Carol did know what was in it:

But we still could not figure out the reaction that had occurred. Carol's class made their own from the ingredients and it worked fairly well, though not as well as the commercially available ones.

Now, who can find the reaction?  Thanks, Carol.

Chris Etapa [Gunsaulas Academy]           Some Fabulous Information
Chris just finished a program at UIC (inherited from Northwestern) called "Get a Grip". UIC sends engineering graduate students into a class (from 5th to 10th grades) and helps the students design and build a prosthetic arm (for poor countries; ie, inexpensively). A kit is supplied to the class with common materials (PVC pipe, clamps, rope, etc.); arms are designed for several different tasks (eg, carrying water, picking up small objects).

UIC is looking for more partner schools; for now, UIC funds the program directly. Chris will bring us pictures/examples to share next time.

Chris also shared information about another project in which she is involved (sponsored by the World Food Organization) in which plants are grown in "grow boxes" and classes are partnered with classes in other parts of the US and other parts of the world to share their experiences. Each box is about $74 (shipping included) and works for three years. Various vegetables can be grown in the grow boxes.

Notes prepared by Benjamin Stark.