Jyotiben Desai [Du Sable HS]
Mining for Peanuts [handout]
J Desai helped us celebrate Earth Day [22 April 2003 -- TODAY!] with her activity. Each group put several glass marbles into a TV dinner tray, and then covered them with potting soil, raking the potting soil over the marbles so that they could not be seen. Each group also made a map of the locations of their marbles. We then exchanged trays, and mined for marbles! for about 5 minutes. We used small objects, such as paper clips, Popsicle® sticks, and coffee stirrers. as probes. Finally the trays were returned to the original group that planted them, who assessed now much damage was done to the soil surface by this mining operation. It is a reminder that activities that provide benefit to society, such as digging marbles, can have undesirable, and often unanticipated, side effects. Putting layers of soil, then sand, then soil over the marbles would be a more complicated, but perhaps better, model of mining, since the disturbance of the soil by our mining operations would have been much more visible and much more difficult to restore. Use of peanuts instead of marbles is another suggestion. The peanuts, when found, could be shelled, and the shells collected as a model of the waste (tailings, slag, polluted water, particulates) produced from mining operations.
A very good lesson on conservation. This lesson appears in the following book, (p 222):
Holt Environmental Science [1996: ISBN 0-03-003133-8]
Holt, Rinehart and Winston, Inc
1120 South Capital of Texas Highway
Austin, Texas 78746
Comment by PJ: The peanut plant, like the soybean, is a legume, which enriches the soil though nitrogen fixation. Farmers typically plant in rows, use a type of turning plow to turn over the edible subterranean nodules [often called goober peas in the 19th century, and referred to as peanuts today]. Some time later the rest of the plant is plowed into the ground to encourage aeration of the soil and composting of organic material. Legumes actually enrich the soil when cultivated in this way --- in contrast to potato farming, which removes vast amounts of nutrients with each crop.
Great job. Thanks, J!
Christine Scott [Beethoven School] and Lilla
Green [Hartigan School,
Chris and Lilla began by leading us through a free expression session about our ideas and concepts relating to soup. Then, they broke the 'orrible news: we weren't going to get to eat some soup, but to roll soup cans down inclines! Chris and Lilla produced several different cans of soup [broth, cream, chunky] and set up plywood ramps [about 4 feet long --- 1.2 meters, and 12 inches wide --- 30 cm]. These ramps were supported on a horizontal surface with a short stack of books at one end. Each regular group rolled each can down the ramp three times, and measured how long it took-- starting from rest -- to travel the length of the board. Results (averages of the three trials) were then compared, the broth can moving fastest for all three groups [Note: If more books had been put under the elevated end of the ramp, the soup cans would have rolled more quickly.]
A control group was first given a long plastic jar that was about 1/3 filled with powdered cleaner --- they found that it would roll for only a short distance -- after which it stopped, requiring a strong push to roll further. That control group next took a jar filled with a liquid, which rolled easily without additional pushing. They took a little scouring powder from a nearly empty can, and rubbed it on the jar to make suds. The jar rolled faster as a consequence. Finally, the control group rolled the empty open scouring powder can down the plane, and it wasn't particularly fast.
Various contributing factors were discussed --- diameters of the cans, masses of the cans, viscosity [flowing ability] of the contents of the can, and friction of the cans on the board. The discussion revealed that the nature of the contents in a sealed can were very important, although friction did determine whether the can would or would not roll without slipping down the incline.
Next they took two long Inertia Rods (a red one and a blue one), which were shown to be of equal weight by taping them to each end of a meter stick, and then finding that the stick balanced when supported at the middle --- the 50 cm mark. Two hapless volunteers were given the task of holding one of the rods in the middle, and then of rotating the rod back-and-forth in a plane perpendicular to their outstretched arms; i.e. wiggling the rod in a torsional mode. The blue rod was decidedly more difficult to wiggle, according to the volunteer who received it. We felt that the weight inside the blue rod was more unevenly distributed --- with more mass closer to the ends of the rod, than for the red rod. Wow -- wee!
We concluded that the broth can rolled fastest because, like the red bar, its mass was uniformly distributed. In the chunky soup can there presumably were chunks near the perimeter of the inside of the can, like the blue bar, which slowed its rolling. Is that correct, or are there other reasons as well?
True or False: What's soup for the goose is soup for the
You had quite a roll today. Thanks, Chris and Lilla!
Marva Anyanwu [Wendell Green School]
Potatoes on the Desk
Marva placed three potatoes on the desk, and asked what students would say [or think!] if they saw them on the teacher/s desk when they first came into the classroom. Various ideas were suggested. She then stated that we would use them to describe and visualize the process known as cloning. When we cut out a little piece of potato containing an "eye", we might expect to be able to grow a potato exactly like the old one, since the DNA should be identical to the original potato. However, we actually would produce a new plant, with an identifiably different potato (tubers). How could that be? Ben Stark [IIT] then led a discussion of cloning, including a more extended description of cloning in plants, cloning in animals, and the famous cloned sheep, Dolly! For additional information on cloning, see, for example Beyond Jurassic Park: Real Science with Ancient DNA http://www.plantmanagementnetwork.org/pub/php/review/ancientdna/ and the Scientific American News Scan feature: Ma's Eyes; Not her ways [April 2003] http://www.sciam.com/article.cfm?colID=5&articleID=000DE213-6B0F-1E61-A98A809EC5880105.
Very nice, Marva!
Notes taken by Ken Schug.