Pam Moy (Morgan Park HS)
showed us a jar containing a green fluid. It was an extract made by soaking spinach leaves in ethyl alcohol for a week (one day was sufficient to leach out the color). She gave each group of two of us an 8 oz styrofoam cup into which the dark green spinach extract was poured to a depth of about one inch. A strip of coffee filter was placed with bottom end submerged in the extract, and the top end taped to side of the cup. Then we went on to the next presentation, and after about an hour and ten minutes we came back to this experiment and observed the strips. There was a dark green band of color at the bottom, then a light green band followed by a yellow band. The process we had performed is called "chromatography," and the strips with the colored bands are called chromatograms. The differently colored bands come from different chemical pigments in the spinach (chlorophylls, etc), which diffuse at different rates through the wet paper strip.
An inexpensive but most informative experiment, and a great introduction to many topics: chromatography; plant chemistry; diffusion rates of different molecules; color differences associated with different molecules...and probably others. For additional ideas see the website http://www.chemguide.co.uk/analysis/chromatography/paper.html Thanks, Pam!
Marva Anyanwu (Green School)
posed the problem: What effects does exercise have on respiration? In respiration
Food + O2 ---> CO2 + H2O + energy
which takes place inside cells in mitochondria. Breathing is moving air in and out of the lungs, but respiration is as described in the prior sentence. Marva asked groups of us to do an experiment. We used a bromothymol blue (BTB) indicator to measure respiration rate, and we predicted that exercise would increase the rate that BTB would change its color in response to increased respiration.
Each group had two clear plastic cups containing BTB which was initially blue. A straw was placed in each cup. The idea was that as a volunteer exhaled through the straw and into the liquid, starting at time zero, CO2 was added to the liquid (from the breath of the volunteer), and the pH would decrease (because of formation of carbonic acid, H2CO3), so the color would change from blue to green to yellow. Two trials were run; one with the volunteer at rest, the other after the volunteer ran in place for 3 minutes. The experiment worked pretty much as expected, but there were complicating factors.
We found that CO2 in the the room air caused the BTB solution to turn yellow on its own, without exhalation. As we exercised, we produced more CO2 in each breath, which caused the BTB to turn yellow in a shorter time. But - with more breaths in a given time, wouldn't more CO2 be expected after exercise? Ken Schug suggested adding water from a closed container just before the test, and adding the BTB just before the test. Or, put a cover over the container to slow (but not eliminate) CO2 dissolution. For additional details see the website http://www.sciencebuddies.org/mentoring/project_ideas/Zoo_p013.shtml.
Marva showed us how to put chemistry to work to measure biological a biological process. Beautiful stuff, Marva! Thanks!
Chris Etapa (Gunsaulus Academy)
brought us a surprise (something alive!) in a cardboard (Xerox paper) box. It was something from her "zoo" at home, and she uses it to teach geometry, observation skills, what animals want versus what they need, etc. She then introduced us to Pythagoras, a male, red-tail boa constrictor snake, about 5 years old and 6 feet long!! Chris said that if she would turn off the heater that keeps him warm, he would go into hibernation for about 3 months. He sheds his skin in one piece, and collecting and saving the shed skins provides a record of growth.
We discussed and examined Pythagoras, Chris described his habits/behavior. His skin patterns (diamond or rhombus - geometry!), and she also used him as a model for kids to calculate his volume (more geometry & algebra). He eats about one mouse per week, but he would eat more, given the chance. For more information see the website http://www.belizezoo.org/zoo/zoo/herps/boa/boa2.html.
PJ comment: the original Pythagoreans were vegetarians; see the website http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Pythagoras.html.
What an exciting and interesting lesson; a sure fire way to get student attention, and create an interest in learning. Thanks, Chris!
What is going to happen next?!
DON'T MISS IT!
Notes taken by Ben Stark