High School Biology Chemistry SMILE Meeting
03 December
Prepared by Porter Johnson

Pushpa Bahl [Collins HS] TITRATION
Pushpa provided several handouts of background information and directions for a hands-on exercise we would be doing later. She announced that there was a "scientific mistake" on the directions sheet and offered a $2 reward (which she showed us) to the first person to discover it. After several false alarms the oldest person in the room noticed that the word "millimeters" had been used where "milliliters" was intended and claimed the prize. Pushpa described a "drop counting" method for doing titration, which is safer and less expensive (though less precise) than using burettes. She then said we would be doing an acid-base, neutralization reaction (Acid + Base ® Salt + Water), specifically:

HCl + NaOH ® NaCl + H₂O. We counted out 10 drops of "unknown" HCl (hydrochloric acid) into a "well" in the Chemplate™ , added one drop of phenolphthalein "indicator" (this compound is pink in basic solution and colorless in acid.) We then added the NaOH (sodium hydroxide) solution while stirring until the solution turned (and stayed) pink. The concentration (conc) of the acid could then be calculated from the following relationship: # drops of base / # drops of acid = conc of acid / conc of base Pushpa, assisted by others, then tried the "egg in a bottle" demonstration of air pressure and was eventually successful in getting a shelled, hard-boiled egg to enter a juice bottle with an opening smaller than the egg without pushing it. They dropped a burning piece of paper into the jar and placed the egg gently in the opening. At first nothing happened, then we saw the egg slowly slide into the jar untouched by human hands! We were not as successful at removing the egg (by blowing into the inverted bottle) and decided that the demonstration would work better with a larger container. [The burning paper heats the air in the bottle, so when the egg blocks the entrance and the air cools, the pressure decreases and becomes less than the atmospheric pressure outside the jar, which pushes the egg into the jar.] Good stuff, Pushpa!

Carl Martikean [Wallace HS, Gary IN] CATALYSTS
Carl wrote these words Jersey, Guernsey, ***Angus on the board and asked us what it was. After a couple of rejected answers, the oldest person present (who had seen this before), said "that looks like a cattle list". Carl said, "that's right!--- and today I am going to use some catalysts". --- this was followed by loud groans! He then demonstrated several ways to catalyze the decomposition of hydrogen peroxide , H₂O₂, using a more concentrated solution (probably 6% by weight and sold as a bleach in hair product shops) than the 3% solution sold at drugstores. In each case he added some bubble soap solution to the hydrogen peroxide, before adding the catalyst, to produce a foam when oxygen gas is formed (the reaction produces oxygen gas and water). The catalysts used were dry yeast (which contains biological catalysts called enzymes), manganese dioxide [MnO₂] (with a surface that can act as a catalyst), and some sodium iodide [NaI] (where the iodide ion [I^-] is present), into the catalyst. He used the "glowing splint" method to verify that the gas formed really was oxygen. He then demonstrated another way to produce oxygen by adding some cobalt chloride [CoCl₂] solution to household bleach. Finally, he enlisted our help in cleaning some grungy looking pennies by immersing them in acetic acid solution (CH₃COOH: vinegar); not much happened until we added a pinch of salt (NaCl: sodium chloride) to act as a catalyst, after which the pennies sparkled like new! [*** Carl surely meant to say Aberdeen Angus, although he should not have ignored the Holstein Frisian breed -- PJ!] Nice work, Carl!

We began some informal scientific discussions, which we will follow up in our next meeting: stay tuned! See you next time (10 December)!

Notes taken by Ken Schug.