James V. DeRosel Marple Newtown School Dlstrlct Newtown Square. PA 19073
I
Students are more likely to find chemistry understandable and interesting if their knowledge of chemicals and the major principles of chemistry has been buttressed with firsthand experiences in the laboratory. Yet, chemistry teachers generally encounter a prohlem in providing students with sufficient number of interesting, informative, thought-stimulating laboratory experiences which make extensive use of chemicals and the methods of science. Demonstrations performed by teachers and laboratory experiments performed by students are commonly used to a r ~ u n i n tstu&nts with th; reality dchemicalsand their reactims. Hot11 are eitertive in providing experience with the real world of chemicals, although the experience provided by demonstrations is primarily vicarious. Laboratory experiments and demonstrations can be used in teacher-paced classes hut only laboratory experiments can be used in selfpaced classes. Thus, for self-paced classes the problem of providing more firsthand experiences with chemicals focused on discovering, formulating, and/or understanding major concepts is both more obvious and more acute. Our response to the problem was to develop "demonstrations" which students can do themselves. "Demonstrations," named See-for-Yourself Exercises, are written with laboratory activities to be completed, observations to be made, leading questions to he answered, and inferences to be drawn by the students themselves. Each See-for-Yourself Exercise is written to reflect the empirical philosophy illustrated hy the response William Harvey2 made in 1636 to a critic who had ridiculed his observations and findings ". . . I beg of you to observe.. mv" learned.. mv frtend.. if . vou would see with . im~artial . y u r own cyci the things 1 aifirm . . ." Each student is similarlv advised to"see-for-vourselt" rather than simplv . . to read what others have observed and concluded. Each See-for-Yourself Exercise is designed to h e l students ~ achieve a specific behavioral objective 'nd to provide experimental support for a generalization or a concept. The student gains practiEa~experience with chemicals, has the opportunity to evaluate his experience, and seeks the broader meaning which has been huilt into the exercise. The data as a whole will have significance which the student can determine. In essence, the student is provided with chemicals, directed to interact them in specific ways, asked to ohsewe the separate results, and expected to draw some eeneralizine conclusion. ~ h e ~ e e - f o r - y o u r s e~l fx e h e havesimilar s formats. Students are told what equipment and chemicals will be needed. Whenever new reactions are to be observed, or it is unreasonable to expect the student to identify all the products. equations arep-iven. Directions are given'to certain operations as well as to make and record observations. Although the time required to complete See-for-Yourself Exercises may range from less than one period to three or more, most of the separate activities within an exercise can he completed within a few minutes. And measurements do not reauire a lot of time or unusual care. See-for-Yourself Exercises have been written on such topics as bondine. exothermic and endothermic reactions. ionic reacrimz a n i net equations, and periodic rable,sulubility rules, half cells and swndnrd rlcctnwic ixmmtiali. There is no limit to the number of topics for whichsee-for-yourself ~ x e r c i s e s 70 1 Journal of Chemical Education
To See for Yourself
can he written; only time, a hit of ingenuity and persistence are necessary. Some exercises stem from original ideas; others are adaptations of one or more published demonstrations. All go through continuous revisions as a consequence of comments from students and new ideas. Two relatively short, hut quite different, examples to illustrate the nature of See-for-Yourself Exercises follow. The first is an adaptation of a Chemical Bond Approach demonstrationVesigned to provide experience with Hess's Law; the second is orieinal and is intended to show the relationship betwrmener&and thccolorsof light emitted by the hot !,ire in nn elrctrtc hrht ttull~.Euchexrr
