High School Biology-Chemistry SMILE Meeting
07 May 2002
Notes Prepared by Porter Johnson

Christine Etapa (Gunsaulus Academy) -- Teaching Atoms
Chris divided the lesson into these three parts:

  1. First, Chris described a recent exercise with students in her class:
    She took the class to the school yard, and some played the role of protons or of neutrons.  These two groups were tightly huddled to form a central nucleus, with protons rotating clockwise and neutrons rotating counterclockwise to distinguish one type of particle from another. Other students (representing electrons) moved in circular orbital paths about the nucleus. The inner circles represented the lower energy levels, whereas outer circles represented higher energy levels.  Altogether this is a model for one atom. As an extension of this lesson, one could use the "student mass aggregate" to model two atoms, which then could form a compound by sharing valence electrons with one another, either through "time sharing" [covalent bonding] or by "leave of absence" [ionic bonding].
  2. Next, Chris had us form the Helium4 atom, which consists of 2 protons and 2 neutrons in the nucleus, and 2 electrons lying in the same circular track about the nucleus. Then we modeled the [highly unstable isotope of a cumulatively toxic semi-metallic element] Beryllium8 atom, with 4 protons, 4 neutrons, and 4 electrons in two different tracks.
  3. Finally, Chris described a modification in which tennis balls are used to represent valence electrons -- after all, the electrons are much lighter than protons and neutrons -- whereas a student represents the rest of the atom. For covalent bonding, two oxygen atoms [students under disguise, in reality] hold onto the same electron [tennis ball]. For ionic bonding of say, sodium chloride, the sodium atom [Na: represented by a soapy and squeaky-clean student] throws its valence electron [disguised as a tennis ball] to the chlorine atom [Cl represented by a sour and caustic student], representing the reaction
    Na Cl ® Na + + Cl -
What a dynamic way to involve students in learning!  Great stuff, Chris!

Therese Donatello (ST Edwards School, Elmwood Park) -- Porosity revisited
Terry continued the discussion of porosity of materials, which was begun in the 02 April 2002 class by Erma Lee. Whether materials such as soil are composed of rocks or very fine particles, there is always some space between the pieces of solid material.  This empty space, called pore space, is the subject of the investigation. She filled identical vessels with plastic beads of various diameters, and then measured the amount of water required to fill the container.  She determined the porosity, as given by the ratio of the volume of water added to the total volume of the container.  We obtained the following results:

Diameter of Bead         Porosity
12 mm      0.53
7 mm      0.42
4 mm      0.43

Ken Schug pointed out that for large containers, these porosities should all be the same, since the beads have the same spherical shape, and the fraction of empty space should be independent of the bead diameter.  The discrepancy occurs here for the largest beads, because our vessels have a volume of only about 50 ml.  Very absorbing lesson, Terry!

Tyrethis Penrice (Oak Park School System) -- Electricity and Magnetism
Tyrethis gave a handout on Electrostatics, which covers some of the same material as the SCETV National Teacher Training Institute website on Static Electricity [ http://www.scetv.org/ntti/lessons/1999lessons/staticelec.html], an excerpt of which is given below:

  1. "Tie about 10 inches of thread around a piece of cereal. Suspend the cereal so that it does not hang close to anything else. (Your partner can hold (it) or attach (it) to the side of the desk.)"
  2. "Charge the comb by rubbing it vigorously with the wool."
  3. "Slowly bring the comb near the cereal. It will swing to touch the comb. Hold it still until the cereal jumps away by itself."
  4. "Now try to touch the comb to the cereal again. It will move away as the comb approaches."
"Rubbing the comb with the wool moved the electrons from the wool to the comb. The comb had a negative charge. The neutral cereal was attracted to it. When they touched, electrons slowly moved from the comb to the cereal. Now both objects have the same negative charge, and the cereal is repelled."
This led us to a discussion of the similarities and differences in static charges and magnets.  Ken Schug showed how to turn an un-magnetized steel nail into a temporary magnet, just by holding it against a permanent magnet.

Marva Anyanwu (Green Elementary school) -- The Secret of the Speeding Boat
Marva illustrated the concepts of surface tension, cohesion [water attracted to water], and adhesion [water attracted to paper] by using paper "boats" floating on water inside plastic boxes. The idea is to cut the boat with a V shape in the back, let it float on the surface of the water in the boxes, and then put one drop of liquid detergent on the water surface behind the boat, right at the apex of the V.  The boat will jet forward. For a similar exercise, see the lesson #1 by John Scavo on Surface Tension, on the SMART Program home page, http://www.iit.edu/~smart/. Neat-o, Marva

Mary Scott (Williams School) -- Black Magic
Mary led us through an application of paper chromatography to determine the different components of pigmentation in the ink in a black, water-soluble magic marker. First, she cut a closed paper ring from a coffee filter, and made an arc around the upper rim of the ring with the black marker.  Next, She placed that ring   into a clear plastic cup containing a little water in its bottom, with the marked arc on  the  paper strip lying above the level of water in the cup.  A few minutes after she left the paper in the cup, the water mark on the coffee filter began to rise because of capillary action.  The component colors in the ink began to separate; she had constructed an "ascending chromatograph".  So, black is colorful as well as beautiful!  For more details, see the Exploratorium Museum website:  http://www.exploratorium.edu/science_explorer/black_magic.html. Thank you, Mary

Brenda Wall (Williams School, 4th Grade) -- Slick Sliding Soap
Brenda gave a handout of a lesson prepared by Judy Schneider -- with the assistance of science teachers at Chester A Nimitz Middle School -- 
LA Unified School District, which are available on the Science Project of the Week website:  http://spow.org.  The lesson, which involves studying whether soap slides better with hand lotion, water, or cooking oil, is also available on The Lesson Plans Page website:  http://www.lessonplanspage.com/.  The specific location of this lesson is http://www.lessonplanspage.com/ScienceExWhatMakesSoapSlideMO68.htm.  Interesting, Brenda!

See you in September!

Notes taken by Ben Stark.