Carol Giles [Collins HS]      BOBBING MOTHBALLS
Carol set the stage for her presentation by informing us that we were a "cognitively delayed", 9-12 class in the third week of Earth Science. She called each group to collect and take to their seats the following items: a large (500 or 1000 mL) plastic graduated cylinder all nearly filled, but with varying amounts of water, 3 or 4 moth-balls, and a small packet containing "effervescent tablets" (say, generic Alka-SeltzerŪ). We all showed we could follow directions by adding one mothball and watched them sink to the bottom. We then dropped in one of the tablets, noticed bubbles of gas "escaping" from them and "oohed " as the mothball rose to the top and hung near the surface. We then added the other mothballs, which soon joined the original one at the surface of the water. After a few minutes the fizzing stopped and the balls dropped to the bottom, only to be reactivated when we added the other tablet. Carol told us to observe closely; when we did, we could see many bubbles of gas adhering to the moth balls at the surface but with only a few bubbles on the mothballs after they sank. We figured out that the gas bubbles made the mothballs "lighter", or, more scientifically, decreased the average density of the moth balls so they became less dense than water and (like a submerged piece of wood) floated to the top. (When the bubbles escape, either by joining the atmosphere or dissolving in the water, they sink.) Carol then passed out sheets containing the procedure, and told us that in her classes students use the back of the handout to write a one page lab report using a standard outline (which she put on the board):  Purpose ... Hypothesis ... Conclusion. Similar phenomena can be observed by adding (fresh) raisins to clear soda pop (often described as sewer lice)  to catch students' attention!  In this case the dissolved carbon dioxide in the soda does the "lifting". The effervescent tablets probably contain sodium bicarbonate (baking soda) and a weak "edible" organic acid which react to form carbon dioxide which is only slightly soluble in water except at high pressure. Thanks, Carol, for good ideas -- and an uplifting experience!

Frana Allen [Skinner School]       SQUIRMY WORM
Frana Allen (the inimitable) then led us through an exercise, starting with the culinary version involving gummy worms and "soil" made from crumbled OreosŪ she bought on sale. Then, having gotten us interested and having touched the gummy worms, she brought out the live night crawlers, with rubber gloves for the ultra-squeamish ("But the worms should be more afraid of us than we are of them", many of us thought.) We did two types of experiment with the live worms: reaction to different surfaces (sandpaper, waxed paper. white paper, brown paper, and warm wet cloth) and light (using a flashlight as our research instrument). There seemed to be agreement that the worms tried to leave the dry rough surface of the sandpaper, and seemed more relaxed on the wet towel -- which is consistent with their native underground habitat. Three cheers for your down-to earth, phenomenological activity, Frana!.

Estellvenia Sanders [Chicago Vocational HS]       BILINGUAL BIOLOGY
Estellvenia put a list of science terms on the whiteboard ---  Acid, base, etc, --- then faced us, and began shouting and flailing her arms around! (I was worried and started to go for help until I realized she was repeating the words on the list accompanied by signing the same words.)  She then used the words in two mini-lectures, first in English then in Spanish and told us about new educational challenges at her school as the population becomes more culturally (and linguistically) diverse. But we aren't worried, it was clear she would be able to cope! Thanks for sharing with us, Estellvenia.

Tyrethis Penrice [Oak Park Elementary Schools]        FULL OF HOT AIR
Tyrethis told us we were full of hot air. Actually, that was the title of her presentation (though she may have been thinking that about us!).  She asked us some questions about balloons and hot air to get us started, accepting any answer because she was just warming us up for the main act! Tye placed a balloon over the neck of a 2 L pop bottle,  then poured hot water over a small part of the bottle. We could see the balloon inflate slightly, and then deflate when she used cold water in the same way. Gary cranked things up a bit by half immersing the bottle in the hot water in the coffee urn, and he got the balloon up to about 4 inches in diameter (again reversing when it cooled down). It was explained that the expansion of a gas when heated is due to the fact that the molecules move faster, which not only causes more collisions per second on the walls of the container, but also gives more push per collision.  In a related activity, several of us did a  "hot hand Luke demonstration, in which the screw cap on a small pop bottle was moistened and placed upside down over the neck opening.  We then placed our hands gently around the bottle (no squeezing, over there!), and we were rewarded by the cap doing a little dance as the expanding air forced its way through the thin film of water to escape. Thanks, Tye, for showing us how much can be taught with simple, inexpensive everyday items,  

 See you next time (19 November)!