Reform of Chemical Education in Holland Jan G. Hondebrink, SLO (Foundation for Curriculum Development, Postbus 2041, 7500 CA Enschede, The Netherlands This article deals with some aspects of the reform of chemical education in the Netherlands. These aspects include the reason for the reform and the results of the effort. Examples regarding the way entropy is treated and the treatment of quantitative chemical problems are given. Background American programs like 'ChemStudy", English programs like ' N ~ f f i e l d and ' ~ Scottish programs like 'Chemistry Takes Shape'Qave had their influence on chemistry teachers in Holland. Many teachers expressed complaints about the existing curricula. These complaints were focused on the first year of chemistry at the secondary level. About two-thirds of all 14 or 15-year-old students are required to take chemistry in the 3rd year for 2 periods of 50 min a week. After this first year, additional courses in chemistry are optional. The program in the initial chemistry course was not attuned to pupils who would not continue with this subject. The consequences were that, for the majority of pupils, chemistry was perceived as difficult and seemingly useless. In later life they hardly remember anything about it. Yet as individuals and as citizens they are confronted with chemical phenomena and problems. There were also complaints about the choice of topics presented and the lack of time to do labwork. Chemistry was usually taught on a very theoretical basis, hardly connected to real experiences. The Process of Reform In 1968 a committee was set up, CMLS (the Committee for the Modernization of the Chemistry Curricula), which was financed by the Ministry of Education. CMLS was to recommend new chemistry curricula for the different levels of secondary education and to suggest a new program for the final examinations. These final examinations are nationwide
and have, understandably, a strong influence on the teaching of chemistry. The work started with the "top-stream" of secondary education, v.w.o., which means "education preparing.for university." This level of education requires six years of secondary education. After the compulsory course of chemistry in the 3rd year of secondary school (called 3-vwo), three more years of chemistry can he chosen: in 4-vwo,5-vwo and 6 . ~ 0 , which have, respectively, 3,3 and 4 periods a week, after which the final examination takes place. In order to formulate a recommendation that would he acceptable to the majority of teachers, CMLS set up experiments in the way ChemStudy had done-with the teachers from 15 schools (this later mew to 50), working on the construction, Box 1. What are the Advantages 01 This Curriculum Develo~mentProcedure7 1. It makes certain that the new curriculum is oracticaiiv. aooiicabie. .. 2. it ma685 cena n that the new curroc" m o o e n not go oeyondthealloledt me. (Asa r.le, exper encc snows tnat thelreatment of atop:c requires more time than was scheduled). 3. resuit is not only a change in topics (sometopics are new, some topics have been ien out) but also there is the opportunity tor new approachesto traditional topics. Educationallythere is a strong link between the content of a topic and the way the topic is presented. 4 Genera alms are cia, Ilea by dew oplng concrete texts 5 Teachers in one scnw are codperatmg more Tncrc or a so a mwement towards a r dsr Lnderstanolngof ea-cat onal problems in general. 6. The quality of the texh is good because of the extensive trials and revisions. 7. A complete text and teacher's guide is inviting for other teachers: they can immediately use this example of the new curriculum. ~
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Box 2. Entropy in Secondary Education it is not advisable to introduce thermodynamics in secondary education. What one can do, however, is to give a "mostly intuitive" idea of why reactions a processssdo a d o not proceed and why dynamic equilibria exist We found mat this can be attained in the following way. intuitively pupils tend to see the decrease of energy (or enthalpy as you wish) as a "driving force" in a process or a reaction. (it is not clear why they do that). Confrontedwith examples of spontaneous processes in which there is no energy change (e.g. the mixing of gases) or which are even endothermic (e.g. the evaporation of water. the dissolution of ammonium nitrate). ~ u ~ come i i s to realize b t U w e must be anolner or vlng l a c e We mrght call thls me drwngfarm lo more rammness. wn cn 1s easl y e*p amed from me 8dea b t mo em or do move. Withthe help of simple statistical probabilities, lhe idea of entropy can be grasped. A gaad example is the prediction ai the outwme of a thmw with 100 dice; this is about350, amean, or bener, a "middle" outcome. There is nothing mystical about it: it is justthat thereareso many more possibilities for the dice to show up 350 b n to give me ememe values 100 a 600. In the same wavthe molecules which constitute a substance wili havea"middie" ranoamness 00 posdm an0 o m molnon Sothe drnv ng force' to moreentropy ts a res.6 d hlaws ol proomeltoes nt. t veiy t can ce felt t m l an ncrease in temperature wili result in a "strengthening" of the driving force to more enbopy. in dynamic equilibria both driving forces are at work. Their "sbength' is equai. me reaction to one side is favored by an increase in enbopy. the reverse reaction is favored by a decrease in energy (enthalpy).
Togethwr with the relation between lhe concentrations in an equilibrium (4, it is possible tounderstand and predict shifts in chemical equilibria without Le Chatelier's principle. Take, for example. the well known ammonia equilibrium:
2 NH&) t Ndg) + 3 The driving force for the reactionto the right hand side of the equation is lhe increase in enbaov lmore molecules in the aas " state1 The drivim iwce for the reactcon to me leh .s&I owease n energy blreanan s oxothermc At aq.lltbrl~m both react ons proceea woth me same speea bath ar vmg forces are equai in 'strength'. When the temperature is increased the driving force for more entropy is enlarged, so the equilibrium shifts to the right towards a new state of equilibrium. The effects an this equilibrium when Concentrationsare changed (e.g., by changing the pressure) can be predicted with the equation
mi5 appmach has merit f a a better undemanding of processes in general. and it provides a basis f w an evenhlai wnfrontation with thermodynamics in university courses which, as we all experienced, is not a smooth affair
Volume 58
Number 11 November 1981
983
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Box 3. A n Example 01 a n Examlnatlon Ouesflon When equal volumes of 0.2 Msodium thiosulfateand 0.2 Mhydrochloric wilh iodine solution. The later these samples were t i i t e d , the more iodine scad are mixed, a light turbidity appears anw about half a minute. aflw whid, war needed. The last sample t w k about 30% m(ne iodine hthe first one. the solution araduallv becomes less transoarent. Iodine converts hydrogen thiasulfuate into telrathionate (&062-) and hyh e h r o oaty can be expla ned by assuming t b t hydmgen Ihiosulfate ons drogen sulfite into sulfate. (HSfl,) formed n Uw soldiw decompose nto hydogen sunne ions (HSOJ C) Write equations representingthereanion of hydrogen thiosulfate with r alter whim these sdlldr a l m s combine to form bagger an0 su f ~ moms. iodine and the reaction of hydrogen sulfite with iodine. sulfur particles. d) Using Scheller and Bohm's results, explain why there is an incubation A t u r b i i i is visible when the wihx patMes consist of at least 10'O s u b period. atoms. Sikma (1977) canied out experiments in which he mixed 10 ml samples of a) Write equations representingthe formation of aulfw atoms in agree 0 IMsodiumthiosulfatesolution wilh 30 ml of hydrochlwic a d of varying ment with this theory. concentrations. He listed the incubation periods (see table): The period of time betweenthe moment the solutions are mixed and the appearance of the turbidity is called Uw inckhtion period. In oder to explain Number mi. of 0.1 M incubation why the twbaiidoes rot appear immediately, seveal scientistshave canied of the sodium thiosulfate hydrochloric period out experiments. One of their hypotheses was that sulfur atoms are being sol". acid in S. experiment formed very rapidly while their combination to panicles large emugh to 1 110 30 ml 0.017 M 84 explain the turbidity, is very slow. 2 10 30 ml 0.033 M 70 A. F. Holleman (1895) mixed 5 rnl of 0.2 Msodium miosulfate solution 3 10 30 m10.067 M 60 with 5 ml of 0.2 M hvdrochloric acid and neutralizedthe solution with 1ml 4 10 30 mlO.lOO M 57 of 1Mpotassium hydroxide solution before the Nrbidity had appeared. Yet he saw the turbidity appear shortly aflerwards. 0 ) In which of these experiments were sodium thiosulfate solution and b) Can this result be in agreement with the hypothesis that sulfur atoms hydrochloric acid mixed in a ratio corresponding to your answer to combine only slowly to farm bigger sulfur particles? Explain youranquestion a? swer. 9 Of What significance are Slkma's results to a further explanation of scheffer and Bohm (1929) mixed 300 ml of 0.010 Msodium thiosulfate Ihe incubation period? solution with 24 ml of hydrochlwic acid. Immediately anerwards they took Explain your answer. a 25 ml sample from the solution and titrated it wilh an iodine solution. Later they look other 25 ml samples from the solution and tilrated these (VWO-examination 1977. With acknowledgments to W. de Vos).
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I evaluation, and r e v i s i o n of n e w t e x t b o o k s and teacher's guides. T h i s process was r e p e a t e d several t i m e s with c o n t i n u o u s coo p e r a t i o n of t h e teachers in t h e t e s t schools. T h e advantages o f t h i s c u r r i c u l u m d e v e l o n m e n t orocess are s h o w n in Box 1. A f t e r m u c h work, t h e ~ M L E So m p l e t e d i t s r e c o m m e n d a t i o n f o r t h e n e w c u r r i c u l u m . t e x t b o o k a n d f i n a l exams. T h e t e x t a n d teacher'sguide were t u r n e d u v e r t u a c o m m e r c i a l f i r m (\Volterr-Noordh(,ft'. C r o n i n z e n ) for f i n a l e d i t i n r a n d d i s t r i b u t i o n . A b o u t 1 5 0 of t h e 5 0 L o - s c h o o l s n o w use these m a terials. The
Future
'I'he M i n i s t r y of K d u c a t i u n i s n o w u s i n g t h e r e c o m m e n d a t i o n s of CM1.S in c o n s t r u c t i n g a n e w c h e m i s t r y c u r r i ( . u I u m for t h e s t a t e schools for v w o a n d n n e w p r o g r a m o f t h e i i n a l e x a m i n a t i o n s in c h e m i a t w . I1 i s expected t h a t hv 19% or 1986 t h i s program will h e to&y i m p i e m e n t e d . ~ i w e v e r in , the m e a n t i m e , t h e n e w t r e n d s c a n a l r e a d y b e seen in t h e e x a m i n a t i o n q u e s t i o n s w h i c h a r e u s e d n o w (see B o x 3). A s i m i l a r p r o c e d u r e i s going o n for c h e m i s t r y at o t h e r levels of secondary e d u c a t i o n . T h i s i s d o n e now by SLO, t h e F o u n d a t i o n f o r c u r r i c u l u m d e v e l o p m e n t , w h i c h r e s u l t e d from a r e o r g a n i z a t i o n by t h e M i n i s t r y of E d u c a t i o n .
Some A s p e c t s o f the N e w Curriculum 1) About %to%ofa l l the lessons involves practical work. Lahwork i s a n integrated p a r t of the curriculum. 2) The program for the first year of chemistry (3-vwo) is mainly aimed at pupils for whom these 66 lessons are the only chemistry lessons they will have. These lessons should be useful for them in later life. M u c h attention is eiven t o chemistrv in dailv life and t o eeneral laws. I t i s a d v i w d ;hat rhepupil,shs;uld he & g r a d u a l l ~ i n t n , ducrd to rhc 'f
