How To Break the Ice with a Ruler First-year a n n l y t u l chcm~strystudents are usually quickly introduced to the need for calihrntmn of volumrtnc glassware and balancer. Normally, the dimrnrlons of an object ore nevkr required--or expected ro br qunted-in a sulmittrd repon. Ew-n tf it were a requirement, calibration ofthe tapr measure or ruler might at heat he rnnv~dcred pedantic. An interesting exercise performed a t the start of every term here a t Pitt takes advantage of these preconceptions as well as the unouestionine faith olaced in the common meter rule hv the maioritv, of .oeoole: A emouo students , ~ of . ir firdt m k ~ dto rnlihrate some clean and contammawd ~d~chlorudimerh~ls~lane-cootrd p ~ p e t susing wnrer and an analytical hnlance. Next, they nrr m w k d to measure t h r length "fa convenient bench :optpreferably about 10 m lung, e n clue that this is really a with 3 wooden meter rule s u p ~ l i e dhy the instmccor. The firit exercise should ~ v them further calibration exercise. ~hev are not told that the ruler has had a 1cm oiece cut from its midsection and then hien reassembled a goad carpmwr ran make the jo~ndlllicult to see, hut an impcrfret jmn r m be cnsily dlscused As a conscqurnce of thw modlficstlon, thc students' measurements and all thew latcr rnlculatmns for area and volume of the hench will be m error. The enerctw is enlctivr in " h r e a k i n rhe ~ ice"at the s t a n ofterm, in introduclnpcallhrntion in a novel way, and in making students adopt a more careful (ie., analytical) approach in future classes. ~~~~
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Michael N. Quigley Chevron Science Center University of Pittsburgh Pittsburgh, PA 15260
Volume 68
Number 4
April 1991
327
