High School Biology Chemistry SMILE Meeting
05 February 2002
Notes Prepared by Porter Johnson

Barbara Pawela (May School; Retired and Still Enthusiastic) It's a Gas
For more details see her lesson on the SMILE website:   http://www.iit.edu/~smile/chbi9916.htm

  1. Barb started out with a hollow, corrugated, flexible tube about 3 feet [1 meter] long and 2 inches [5 cm] in diameter,  swung it around her head, and we heard sounds of various fixed pitches.  Why?
  2. Barb then used a spray bottle to send a few "spritzes"*** of the liquid inside into the air.  When we detected the "perfumish" smell, we raised our hands.  Those closest to Barb detected it first, whereas those in the back didn't smell it until later.  Why?
    ***
    Comment by PJ: "spritzen" is a good German verb, meaning "to squirt, spray, sprinkle, spatter, or inject".  For discussion of this and other "German English" words, see the website GermanEnglishWords.com:S [http://germanenglishwords.com/rlgs.htm].
  3. Barb then set up 3 groups of several participants each.  Each group got a clear plastic bag, like the produce bag in a grocery store.  We "scooped" the bag through the air and then closed it.  Although we could see nothing inside, it bulged like it was full.  How come?
Barb used these three experiments to demonstrate that, even though air is "invisible" it is real and material, and it is involved in innumerable phenomena in physics (sound generation), chemistry (diffusion of perfume), and biology (lung action).

Barb continued with a description of the three states of matter --- (solid, liquid, and gas), and continued with experiments to study the behavior of air as a gas --- more precisely, as a mixture of gases.

  1. She put a candle in a shallow pan of water [H2O], lit it, and covered it completely with a large inverted drinking glass. The flame died out as the oxygen trapped inside the glass was used up in combustion.  Water vapor subsequently began to condense on the glass at the top, and water rose inside the glass. It rose about 11 millimeters, when the initial volume of gas corresponded to about 100 mm.   Why?  
    We concluded that air pressure inside the glass was slightly less than outside, and that the temperature would be about the same after a little while. The chemical reaction in the burning candle is [remember last time?] essentially
    2CH2 (candle hydrocarbon)+ 3 O2 ® 2 CO2  + 2 H2O (condenses as fog)
    Notice that 3 molecules of O2 gas are required to produce 2 molecules of CO2 gas, so that after the water condenses we have fewer gas molecules. Because air consists of less than 20% oxygen, if all the oxygen is expended in the process of combustion, we would have about 13 % carbon dioxide, corresponding to a 7% decrease in the number of gas molecules. Thus, we would expect the gas volume inside the container to be reduced by 7%, and that is approximately what we get.
  2. She put H2O2 (hydrogen peroxide) and yeast inside a test tube, and then connected its mouth to a balloon.  Gas bubbles formed in the tube, and the balloon became partially inflated.  She struck a match [lighting a splint works just as well], then blew it out, and quickly took the balloon off the tube, and quickly put the match inside the tube.  The match re-ignited, because of the additional oxygen produced by the yeast, even though it had cooled somewhat.  The yeast had catalyzed the decomposition of H2O2 into H2O and O2:
    2 H2O2 ® 2 H2O + O2
  3. Barb mixed vinegar ( containing acetic acid --- CH3COOH) and baking soda (sodium bicarbonate  --- NaHCO3) in a bottle, which she quickly enclosed over the lip with a balloon.  As before, the balloon inflated.   She repeated the "match" experiment of Case 2., but was not able to re-ignite the match.  In fact, a lit match was quickly extinguished inside the bottle, because carbon dioxide was being produced.  The chemical reactions in this case are
    CH3COOH + NaHCO3 ® NaCH3COO + H2CO3
    and
    H2CO3 ® CO2 (gas) + H2O.
Very good, Barbara!

Frana Allen (Skinner School, grades 1-5) Circuits
Frana brought in some very neat battery-operated kits (costing about $50 each). The kits, which are called SWITCH ON,  require two AA batteries for operation.  You can order them by email, snail-mail, FAX, or telephone:

SWITCH-ON!
P.O. Box 705
Bellevue, WA 98009
U. S. A.
Phone: (425) 747-7766
Fax: (425) 957-9384
E-mail address: switchon@concentric.net
The kits contain plastic modules of various sorts (wires, resistors, diodes, capacitors, light bulbs, electric motors, musical- alarm- amplifier- circuits, switches, microphones, etc).  Each module has male and female "snap connectors" that simplify assembly of the various circuits.  We played with these kits for some time, and found them to be SENSATIONAL!  Although electrical phenomena are not normally considered to be intrinsic to either biology or chemistry, in fact electricity is basic to the understanding of nerve impulses, synchronization of the beating heart, locomotion, the operation of the brain, seeing, hearing, smelling, and tasting.  Thanks, Frana!

Marva Anyanwu (Green School) [Handout:  Can Light be made by Breaking Sugar Crystals?]
Marva put Wint-o-green Lifesavers™ that contain sugar into a clear plastic bag that she tied shut, darkened the room, and after a minute or so she used pliers to break the lifesavers into pieces.  We looked carefully at the bag while pieces were being crushed, and saw flashes of light.  Why is the light being produced?

Electricity is used to make light in light bulbs, and fireflies make light through chemical processes.  In this case, the light is being produced as a result of mechanical stress [triboluminescence].  The lifesavers contain crystals of sucrose (table sugar), which are broken,  thereby releasing energy.  This energy excites atoms, which then emit a soft blue-white light.  If you prefer, you may simply chew the lifesavers in front of a mirror in a dark room.  The effect is described on the MadSciNetwork of Edible/Inedible Experiment Archive website: http://www.madsci.org/experiments/.  That site also contains the following information:

"Triboluminescence is the mechanical generation of light. Certain chemical bonds will generate light energy when the molecules are torn apart by mechanical crushing. Wintergreen Lifesaver candies contain some of these bonds. No other flavor of lifesaver candy (such as peppermint) will work in this experiment.  You are generating light energy by triboluminescence because each time you chew the candy your teeth are tearing apart the chemical bonds that were formed when the liquid candy was molded into a solid lifesaver. Wintergreen contains molecules that exhibit triboluminescence."

Marva also discussed an article on Stomach Bypass Surgery:  It's a serious step, but they saw gastric bypass as their best hope [20 Jan 2002; Kevin Davis Special to the Chicago Tribune: http://www.chicagotribune.com/].  She explained the procedures for treatment of morbidly obese patients, using a plastic model of the human stomach.  We had a lively discussion.

Good work, Marva!

We had an excellent session, top to bottom, this afternoon!

Notes taken by Ben Stark