R.I.P.I. -What Chemists Do in the Laboratory The need for a short descriptive statement that expresses the essence of what chemists do often presents itself to educators. R.I.P.I., a n acronym for React, Isolate, Purify and Identify, refers to four fundamental processes that are regularly taught to students enrolled in introductory chemistry courses. For some students these processes are part of their laboratory training to be a chemist, for example, when they are asked to prepare and characterize a compound. "React" is self-explanatory - i t is the defining process of a chemist. "I" refers to "Isolate" which is synonymous with the word, "separate." "Isolate" generally involves setting apart substances after a reaction has occurred such as a product from a n excess reactant or from a n unwanted bi-product. Filtration, simple distillation, column ehramatograo h e and liauid-liauid extractions usine a seoaratow funnel are Dart of a chemist's reuertoire of techniaues to isolate Xhtancrs: ~ n eon the~technioie the chkmicals heinb used. usuallv cankin a certain - e ,o e i d i ~ ~ ani~ ~ ~ ~ isolated ~ suhs&nees ~ " amount o f u n ~ a n r c dimpurirws, rhcrk,n.;.Irolaw"r~~r-;hnnd-)":hand i.nh the next pn,ce.is."~ur~iy"Ch~mlrrs punh or rcmow impurirics by n.crysrall~z;rrltrn.ruhlmatlm and fractwnal dlstrllatwn. The last term in the acnqym. "ldtn. rih:"rrfers to drtrrmmmg the delinitwe qual~tattvcm u orquanrifnf~\cchnrncfrr~srirsofa subsrancc and asrertamtng its identity. Melting points, spot tests, titrations, thin Layer and gas chromatography, and spectroscopy are some processes by which chemists characterize a n unknown substance. More general processes such as observing, hypothesizing, reasoning, comparing, synthesizing, etc. which are used when solving problems he i t in or out of the lab, also would he appropriate to discuss with students when presenting R.I.P.I. As written, this acronym describes a cognitive dimension without explicit reference to the affective domain. This latter aspect of the mind is important since chemists do not create in a n emotional vacuum; they become excited with discovery, are proud of their work, often are skeptical, and even become frustrated and stubborn a t times. In other words, chemists' work like others is emotionally laden. To represent this often implicit dimension of laboratory work an "Enfor "emotion" can be affixed to the end of the acronym, giving "R.I.P.I. + E." I t would be well to view R.I.P.I. or R.I.P.I. + E as a flexible conceptualization. Some methods such as distillation can be used to isolate a s well as purify a mixture, while others like computer modeling is not easily categorized. Furthermore. the order of the acronvm does not refer to a fixed seouence of ooerations that chemists alwavs fallow. Some ~~~~.~~~~~~~ chcm:srs, for rhnr mntrrr, nrehnly ~nvolvrd~nm e rspert u f ~ . i . P . l~. w e ; a m p l t ,there a r e w m r uhmm& whole vxprrtlsr I-;predummately ~nvulvedw t h the rdentifiration proccssaxh 3s making nic3surcn~cnts,creatingnualgtical methoduluwes. or dewnnimng arrurrurcs. In short, R I I'I is a eonstnlrt for the oegnnrr. not rralifv In the midst of imoartant details-hemical facts, firures, rules, laws, examples. and exceptions-the *Big Picture" is easily obscured fqom students. R.I.P.I. is a practicai andeasy remember-response to chis academic problem. I t represents broad conceptual domains that teachers can utilize to organize the voluminous and often complex information that confronts a student entering the chemistry laboratory for the first time. ~
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Stephen DeMeo Bamard College, Columbia University New York, NY
932
Journal of Chemical Education
