Pam Moy (Morgan Park HS)
had an "eye opener" for us - she placed on the table an "alien fetus" in a jar. Question: Could this be possible? The point was to get us to practice scientific inquiry by examination of the "specimen" and the give-and-take of the discussion it provoked. It worked, Pam. Thanks!
Chris Etapa (Gunsaulus Academy)
continued on the theme that "things aren't always what they seem". She poured tonic water into beakers. The beakers were placed on white paper and the room was darkened. When she shined white light into a beaker, we saw only white light color. But with UV light we saw a lavender/blue color. It turns out that the quinine in the tonic water absorbs UV light and fluoresces, producing the lavender/blue color. It was somewhat difficult to be sure that the color wasn't coming from the UV light alone. The experiment works best in a very dark room. What a fascinating way to provoke student interest! For more information see http://en.wikipedia.org/wiki/Quinine.
Karlene Joseph (Lane Tech HS)
borrowed from the following book
She filled a glass right up to its rim with water. Then she asked the question:Science Is ...: A source book of fascinating facts, projects, and activities.
Susan V Bosak [Firefly Books 2000 $29.95 List Price]
ISBN 0 - 5907 - 40789
Our estimates ran from 24 to 100. So ... we added paper clips to find the answer. By the time we got to 100, we were all astonished. But then we added still more - and got to 188 clips. The water was bulging over the rim, but it did not spill! Surface tension of the water was the phenomenon illustrated; the water behaved as if its surface was a thin, elastic film, keeping the bulk of the water from spilling over. Next, with a beaker containing water, Karlene used a tweezers to lay a needle gently on the surface of the water, where it floated! Surface tension, again!
Then she added a drop of detergent (dishwashing fluid) to the water, and the needle dropped to the bottom of the beaker. The detergent had practically destroyed the surface tension so the needle was no longer supported by the surface tension "elastic film!" "Let's try it on the water bulging over the rim in the glass with paper clips!" we suggested. So Karlene carefully added a drop of detergent, and sure enough! - the surface tension "film" disappeared, and the water spilled out over the sides of the glass! Finally, Karlene floated a match on the surface of water in a beaker. Then she added a drop of detergent on one side of the match. The match was expected to move to one side as surface tension on that side was reduced, but we weren't sure we could see significant movement. Why didn't this work? But what a fascinating set of experiments to show the reality of surface tension!
Pat Riley (Lincoln Park HS)
showed us how to investigate antacids as bases. Each group of us received 4 resealable plastic sandwich bags. To each we added these ingredients:
Note: Cabbage juice is a chemical indicator of pH by its color. We used a hammer to crush one tablet of each of 4 different antacids, and we then added each to a different bag. We squeezed each bag until the color change caused by the antacid was complete, and recorded the approximate color. If a pH chart for cabbage juice were available, one would match the final color to a particular pH. [See the website http://chemistry.about.com/library/weekly/aa012803a.htm] The color changes as the acid (acetic acid in the vinegar) is neutralized to some extent by the antacid. The color is pink at the start (indicating low or acid pH), but was converted to blue, to green, to yellow (most basic pH) by the antacids. We inferred, from the color changes, that there were different amounts of base (sodium bicarbonate) delivered by the different antacid tablets. Cool!