High School SMILE Meeting
1999-00 -- 05-06 Academic Years
Organic and Polymer Chemistry

06 April 1999: Don Kanner [Lane Tech HS]
Richard Feynman once said "Electrons, in many ways, are like balls". He presented a view of molecular bonds developed by a structural organic chemist some time ago, in which you visualize the bonds themselves as being like little balls; in fact you can made models of these bonds out of styrofoam balls. He began with BENZENE, [aromatic hydrocarbon, petroleum additive, and seriously carcinogenic] which has the chemical formula C6H6 and plane hexagonal structure:

    H           H                  This picture cannot be correct, since
\ / every other Carbon bond is a double
C = C bond, and yet the molecule must have
/ \ six-fold [hexagonal] symmetry Thus,
H -- C C -- H bonds "time share" at the various
\\ // sites, according to the miracle of
C -- C the Quantum Theory. Simple to
/ \ explain, but hard to draw!
H H

Each carbon atom has four "tetrahedral" bonds, as if the C atom were at the center of a regular tetrahedron and the bonds extend to the four vertices. The angle between the directions are all given by A = cos-1[-1/3] = 109.471o

The usual approach is to make the C and H atoms out of little balls of different colors and sizes [OK; gum drops will work just as well], connected by toothpicks. Don pointed out the bonds are large, whereas the core atoms are rather small, and will fit almost anywhere. Thus, you should represent the bonds by styrofoam balls, and forget about the location of the atom. [Gum drops are actually better to use, because you can eat them as you go along; especially when the teacher is not looking!] Then, benzene has 24 bonds, in relevant tetrahedral directions, each represented a styrofoam ball. So it goes!

He also demonstrated the following molecules:


C2H4 ethene [or ethylene for old-fashioned types]
C2H6 ethane
H2O water
CO2 carbon dioxide

This is an absurdly non-conventional viewpoint concerning organic structure [in the words of the Physicist Wolfgang Pauli, "it may not even be wrong!"]. Perhaps we should revise the statement by Feynman to read "bonds, in many ways, are like little balls".

Why? Will this work next year? Why or why not?

21 November 2000: Christine Etapa [Gunsaulus Academy]
brought us into the world of slime.  We made three different kinds of slime [silly putty] following the recipes given out.  In reality we were making polymers and comparing each of the polymers we made.

She led us through the first recipe, [2 grams of Borax, 70 ml of water, and 40 ml of white glue] so that there would be no confusion. To our amazement, right in front or our eyes our mixtures thickened and jelled into polymers.  When we played with our first creation [like putty] it was soft yet pliable and able to bounce.  It was able to "run", but easily cleaned up.

When trying the second recipe [75 ml white glue, 45 ml water, and 1 to 30 grams of talcum powder, and 1 gram of borax, and a few drops of food coloring], the mixture was more solid, like Play Dough or clay.

The third recipe [75 ml glue, 45 ml water, 1 to 30 grams cornstarch, 1 gram Borax, and a few drops of food coloring] was more adhesive than the rest.  It was also quite "runny".

The recipes for the second and third could be adjusted to vary the consistency, and to compare the results.

For more details see these websites:

27 March 2001: Therese Donatello (St Edwards School) Organic Chemistry / Structures
She passed out a handout containing two different structures for the hydrocarbon Pentane [C5H12]:

These two hydrocarbons are isomers, with the same chemical formula but different molecular structure.  In general, they have different chemical properties.  By contrast the hydrocarbon  with a pentagonal carbon structure  C5H10, which has each carbon atom attached to 2 H atoms, is not an isomer of C5H12.  The class considered making various isomers of Butane, C4H10. The group then examined wooden balls with holes in them, to which rods could be attached to build molecular models..  Here is the correspondence of the element in question with the balls

Color Element:
Symbol
Number of Holes: 
Valence
Black Carbon: C 4
Yellow Hydrogen: H 1
Red Oxygen: O 2

Holes in the block represent valence electrons, which can be given or taken. The number of valence electrons to be given or taken is determined by the position of the element in question in the Periodic Table [http://www.ptable.com/].  Models can easily be made for C5H12 [Pentane], C4H10 [Butane], CH3OH [Methanol], C2H5OH [Ethanol], and C3H7OH [Isopropyl Alcohol].  This lesson will be continued next time.

13 March 2001: Therese Donatello (St Edwards School) Organic Chemistry / Structures
She passed out a handout containing two different structures for the hydrocarbon Pentane [C5H12]:

These two hydrocarbons are isomers, with the same chemical formula but different molecular structure.  In general, they have different chemical properties.  By contrast the hydrocarbon  with a pentagonal carbon structure  C5H10, which has each carbon atom attached to 2 H atoms, is not an isomer of C5H12.  The class considered making various isomers of Butane, C4H10. The group then examined wooden balls with holes in them, to which rods could be attached to build molecular models..  Here is the correspondence of the element in question with the balls

Color Element:
Symbol
Number of Holes: 
Valence
Black Carbon: C 4
Yellow Hydrogen: H 1
Red Oxygen: O 2

Holes in the block represent valence electrons, which can be given or taken. The number of valence electrons to be given or taken is determined by the position of the element in question in the Periodic Table [http://www.ptable.com/].  Models can easily be made for C5H12 [Pentane], C4H10 [Butane], CH3OH [Methanol], C2H5OH [Ethanol], and C3H7OH [Isopropyl Alcohol].  This lesson will be continued next time.

10 April 2001: Therese Donatello (St Edwards School) 
reviewed the discussion of organic chemistry begun last time. 

22 January 2002: Benjamin Stark (Biology Department, IIT)
Ben did these two miniteach presentations at this first class of the semester:

  1. The first started with a very simple demonstration.  A glass microscope slide was placed over a candle flame, and we watched attentively as the slide fogged, and then the fog disappeared.  We thought about what the fog was.  One suggestion was "steam", but steam is an invisible gas, and the fog was liquid water [H2O].
    We then asked how we could get liquid H2O from a burning candle.  There were several incorrect suggestions, and the actual answer is that  a chemical reaction occurs when the candle burns.
    2 CH2 + 3 O2 ® 2 H2O + 2 CO2
    The CH2 radical represents the hydrocarbon chain present in the candle, and the H2O represents the fog produced. The carbon dioxide [CO2] escapes as a gas, since it would require a temperature of less than -108°F or -78°C for condensation. The water initially condenses on the slide, since its temperature for condensation must be less than 212°F or 100°C. The heat of the flame causes the fog to evaporate and the slide to be warmed, so that water can no longer condense there.
  2. Using Tinker Toy type molecular models, he illustrated how the atoms are arranged in molecules such as H2O and CO2, and how they are rearranged by chemical reactions. It is this rearrangement of atoms in the burning candle that produces heat and light. We designate this with the following energy diagram
                  ^
|
Increasing | 2CH2 + 3O2 |
Energy | |
| |
| | (heat and light released)
| |
| \ /
| | 2H2O + 2 CO2
|

Karlene Joseph [Lane Tech HS, Biology] then discussed how a very similar chemical reaction

C6H12O6 + 6 O2 ® 6 H2O + 6 CO2
gives living organisms energy. The compound C6H12O6 is glucose [simple sugar]. This overall reaction occurs in many small steps in biological systems, so that the energy can be harvested in small, useful "packets", rather than being released in a "lump" of heat or light. The second miniteach focused on two ears of Indian Corn [the kind with multi-colored kernels].  Some of the kernels had homogeneous colors, whereas others were speckled or striped with different colors.
               ...               \\   ||   //
..... \\ || //
... \\ || //
.. \\||//
\\//
Speckled Striped
Such speckled or striped kernels helped Barbara McClintock discover "mobile genetic elements" or "jumping genes". She received the Nobel Prize in Medicine in 1983 for this discovery.  Each kernel is an individual embryo derived from a single cell.  The genes in such a progenitor cell can be set to give one color.  However, in a cell that is created after several cell divisions have occurred, a "jumping gene" can move and change the genetic makeup so as to change the color of that cell, and all cells subsequently derived from it.  This leads to a patch (speckle or stripe) of cells of the new color on the background of cells with the original color.  Here is a schematic to illustrate the process:
 0: cells of original color
X:: cells of new color due to movement of jumping gene

® Cell Divisions ®
0 ® 00 ® 00 ® 000 ® 000 ® 00000 ® ® ® ® ® "blob"
00 000 00000 000000
00X 00XXX 000000
XXXXXX
original jumping speckled
cell event region
See the websites http://www.ndsu.nodak.edu/instruct/mcclean/plsc431/transelem/trans1.htm and http://www.profiles.nlm.nih.gov/LL/Views/Exhibit/narrative/nobel.html.  

1902-1992 Barbara McClintock. Though American botanist Barbara McClintock conducted the research that led to her discovery of mobile genetic elements in the 940s, it was not until decades later that scientists began to take her work seriously. McClintock experimented with variation in the colors of corn kernels on a single cob. She tracked pigmentation changes in the corn and observed through microscopic evidence that two transposable genes called "controlling elements" were influencing the corn's pigmentation according to where their ever-changing position was on the corn's chromosomes. Whichever enes became the genetic neighbors of these controlling elements in a given generation of corn accounted for the changes in pigmentation McClintock observed. In 1983, McClintock became the first female recipient of the Nobel Prize for Physiology or Medicine. Scientists today believe "jumping genes," or transposons, may be linked to some genetic disorders such as hemophilia, leukemia, and breast cancer, and may have played critical roles in human evolution.
Source:   http://www.pbs.org/wgbh/nova/genome/her_mcc.html

11 March 2003: Barbara Lorde [Attucks Elementary School, science; grades 3-8]      Making a Plastic Toy
Barbara
warmed one cup [250 ml] of milk in a saucepan for a few minutes, and slowly stirred in 5 tablespoons [75 ml] of vinegar.  The casein [a milk protein] and fats separated out, because the drop in pH (increased acidity ) caused them to become insoluble. A rubbery mass was initially formed, but eventually it began to harden into a plastic consistency.  She then added food coloring to the casein during the class, to make it more interesting.  This casein-fat mass can also be squeezed or placed in a mold to produce a "toy" after hardening. She also suggested that you could bring in ratios and proportions in a practical context, as well as convert into metric units.  An interesting Chemistry lesson, as well as  ... 

... artistic, Barbara!

08 April 2003: Ann Parham and Winifred Malvin [Carver Elementary School]      Making Erasers (Handout)
Anna and Winifred
helped us study polymers by making erasers.  We added vinegar to an an aqueous latex solution, with food coloring added for visual enhancement.  We obtained a rubbery solid, avoiding contact with the skin and using eye protection.  We could form the rubbery mass into various different shapes, which would harden upon drying for several hours.

An additional experiment used an abrasive (sand mixed with baking soda) to make an ink eraser (remember them?).  The exercise involved chemical reactions, with acids and bases, polymerization reactions, and modifying the physical properties of polymer obtained.  These lessons come from the book Chain Gang -- The Chemistry of Polymers, which can be obtained from Terrific Science Books, Kits, and More™.  For details see the website http://www.amazon.com/Chain-Gang-Chemistry-Polymers-Science/dp/1883822130.  The table of contents for that book can be seen at the website http://www.amazon.com/Chain-Gang-Chemistry-Polymers-Science/dp/1883822130#reader_1883822130.

Great job, Ann and Winifred!

08 April 2003: Carol Giles [Collins HS]     Styrofoam Packing Nuggets
Carol
shared an exercise she uses in her special education class.  She passed out Styrofoam® packing nuggets, and asked us how many nuggets would dissolve in liquid Methyl Ethyl Ketone (MEK -- CH3-CO-C2H5), a chemical compound closely related to Acetone (Methyl Methyl Ketone -- CH3-CO-CH3).  We watched with awe as handfuls of nuggets were dropped into a beaker with 200 ml of MEK, as they melted down and disappeared.  The original colorless, odorless solution became very dark green, as the pale green nuggets dissolved.  [Note that ordinary  melting involves a change from solid to liquid phase of a material without the addition of other reactants, whereas this is quite different.]  The original nuggets consisted mostly of air, and they actually contain very little polystyrene foam -- Styrofoam®.  Other objects made from Styrofoam® (coffee cups, plates, ... ) can also be used.  Results may vary, when different amounts of MEK are used.  Acetone, a less expensive ketone, may also be used to dissolve Styrofoam®.  Carol uses this exercise to demonstrate the scientific method.

Pat Riley emphasized the importance of doing this experiment in a well-ventilated room, away from heat sources to avoid respiratory distress and inflammation.  [For a description of the hazards of  MEK, see the website http://www.tapplastics.com/msds/pdf/MSDS_MEKS.pdf. Acetone presents similar hazards!Pat suggested an alternative version using water-soluble starch-based packing pellets.

Interesting stuff, Carol!

14 September 2004: Bill Colson [Morgan Park HS, Mathematics]           Magic Powerball
Bill
then passed around a Curiosity Kit [http://www.curiositykits.com/] Magic Powerball , which can be used for making your very own superballs.  He had obtained this as a promotion from Kraft Foods™.  These kits may be ordered at the website http://www.kidsurplus.com (then search for 'Powerball'), from which the following has been abstracted:

"To make these Magic Powerballs™ from Curiosity Kits®, pour the three kinds of crystals (red, green, and blue) into the mold, and then dip in water to make three bouncing 1" Magic Powerballs that soar sky high! Includes green crystals that glow in the dark. Kit includes the Magic Powerball Crystals, resealable plastic bag, Magic Powerball Mold, and illustrated instructions."