“Solving a Chemical Problem” is a laboratory exercise in Exercises and Experiments in Chemistry by Metcalfe Williams and Castka (1978). It is an exercise in the testing of unknown solutions in a systematic manner. Solutions are numbered and the student need not know chemical formulas or reactions to do the experiment or to appreciate the logic involved. We used the experiment early in the course.
The students use the following stock solutions:
| Solution Number | Composition |
| 1 | 1.0 M HCl or H2SO4 |
| 2 | H2O |
| 3 | 1% H2O2 |
| 4 | 0.5 M Na2S2O3 |
Solution T: 1.0 M Kl (added to all solution combinations)
Five drops of solution T are added to 1 mL of the four solutions, first separately, then in all combinations of two, in all combinations of three and finally to the four solutions mixed together in equal volumes. Students had to preplan the combinations to be tested.
The desired “positive” reaction is formation of a light red-brown solution (I2). Students must determine from the reaction data:
- which combination of solutions provided the appropriate product (1, 2, 3 and 1, 3)
- which solution had no effect on the desired reaction (2)
- which solution must be present for the appropriate color to form (1, 3)
- which solution inhibited formation of the desired product (4)
Many students seem to have difficulty grasping the logic to be used in making these determinations. The tendency is to “cookbook” the lab, and think about it later. So, we developed an analogy which was quite effective in clarifying the rationale. It was worked the day before the lab. I call it the “ANTIQUIRK ANALOGY”.
We found that nearly all of the students were able to solve the chemical problem in the laboratory session and were able to clearly explain their reasoning.
Who is the antiquark? - A chemical analogy
Goal:
To determine the identity of the two guys who make up the “Dynamic Duo” (Quark and Quirk), the guy who is the “Antiquirk”, and the poor sap who is “The Moron”.
The aliases:
- SAM
- JOE
- FRED
- BOB
The characters:
- The Dynamic Duo, Quark and Quirk, MUST be together in order to fight for truth, justice and the Kryptonian way. Alone, each isn’t worth $@*&!
- The Antiquirk, in his own dastardly way, renders the Dynamic Duo useless whenever he’s around.
- The Moron is just there. He doesn’t help or hurt anyone.
| The facts | Fact number |
| SAM alone – no action | 1 |
| JOE alone – no action | 2 |
| FRED alone – no action | 3 |
| BOB alone – no action | 4 |
| SAM + JOE – no action | 5 |
| SAM + FRED – ZAP! POW! $#*&! | 6 |
| SAM + BOB – no action | 7 |
| JOE + FRED – no action | 8 |
| JOE + BOB – no action | 9 |
| FRED + BOB – no action | 10 |
| SAM + JOE + FRED – ZAP! POW! $#*&! | 11 |
| SAM + JOE + BOB – no action | 12 |
| SAM + FRED + BOB – no action | 13 |
| JOE + FRED + BOB – no action | 14 |
| ALL FOUR TOGETHER – no action | 15 |
Your findings: Who's who?
Dynamic duo:
The Anitquark:
The Moron:
Feedback
The next day.
The results:
- SAM and FRED are the Dynamic Duo. Of course, it is impossible to tell which is Quark and which is Quirk from the data given. (Fact 6)
- JOE is the Moron. (Fact 11: his presence doesn’t inhibit the Duo)
- BOB is the Antiquirk. (Fact 13: his presence inhibits the Dynamic Duo from going ZAP, POW)
Facts 1 through 4 tell us nothing since we were told that the Dynamic Duo must work together to go into action.
The other facts further support and are consistent with our findings. Often certain information is of KEY importance while other information is a useless burden to us. The logical mind will begin to develop a sense of importance of information presented. It will focus on the key facts and screen out the extra baggage.
(This is a reprint from Chem 13 News, May 1984, page 13.)
