l ( m Workshop on Chemical Education

n f o r o n c i j a o kemijskom obra

C K

•

Split, lOth - 14th November 201

Book of AbstractsKnjiga sažetaka

1. Hrvatska konferencija o kemijskor .inju

l ' Croatian Workshop on Chemical Educat ion

- improving the l inks betvveen schools and universities to ensure that students are more capable of making a

smooth transition to undergraduate degrees in science, engineering and mathematics;

- addressing the perception among prospective students that degrees in these subjects are relatively hard to

succeed in and require too much vvork;

- improving the laboratorv teaching facilities in universities in science and engineering subjects; and

- ensuring that science degrees provide graduates with the skills that emplovers need and value, and that there are

revvarding career paths into further study and academia.

The research results presented at the 10th ECRICE held this year in Krakow (Benneth, 2010) clearly showed that

at the ages betvveen 10 to 14 the students' attitude towards science is a very positive one, with students recognising

enormous benefits of science to the society and life and being eager to study it. Unfortunately, this attitude changes

and, just a few years later at the ages betvveen 15 and 18, the students' general impression is: "Science is good but it

is not for me!" There are a lot of influences underlying such a change in attitude, but one of them is particularlv

significant. This is the claim that "Science is hard to study"! Students do not think (or feel) that they are personallv

capable of being scientists. Although the discouragement of science students is very common there are, hovvever,

exceptions. These exceptions provide us with unique opportunity to recognize good practice and factors that impact

positively the uptake of science by students (strategic, contextual, structural and practical features vvithin schools).

Hopefully, understanding such factors vvill allovv us to amplify them and realize a more constructive approach to

science education. One feature important to the science teaching should be to enable our students to actively do

science - to learn and apply the scientific method.

This can be ensured by a general teaching/learning strategy know as inquiry learning. There are various ways to

implement inquiry leaming in the classroom and one of them is a so far fairly successful variant developed by a

group of Croatian teachers (Judaš, 2010): the small-group discovery-based learning strategy (SGDBLS). In the most

developed version of SGDBLS the teacher is only allovved to ask questions and is not allovved to instruct. The

questions are designed to guide the students to the correct explanation of the presented problem; the students are

forced to use the knovvledge that they already have acquired, to apply it and to discover nevv principle(s) - to learn

new knowledge.

It is a general impression that inquiry learning needs laboratories and sophisticated chemical equipment but

SGDBLS proves that this is not so. This is achieved by using experiments related to very simple everyday problems -

those that are inexpensive and in their essence environmentally friendly (this is also a good way to remain on the

"green chemistry" path). The SGDBLS selects the experiment vvith the purpose to present the problem rather than to

help illustrate a selected topic of content knovvledge. To describe the SGDBLS let us consider a simple and very

well-known experiment - a burning candle under a glass vessel. The experiment is simple, inexpensive and,

unfortunately, is probably one of the most misused experiments in ali the history of teaching science. Although there

is novv a substantial amount of Information available in professional literature providing the correct explanation of

the experimental observation (Birk & Lavvson, 1999; Krnel & Gložar, 2001; Peckham, 1993; Wiederholt & Plemel,

1996; MacNeil & Volaric, 2003) many textbooks and teachers still use this experiment to demonstrate the volume

percentage of oxygen in the air. Instead of using this experiment wrongly to demonstrate such a fact, it is better to

14

enable students to perform the experiment, to write down their observations, to discuss them and then to explain

them. Several observations can be made during this experiment:

- as candle burns the vessel vvalls become warm and cloudy,

- as the flame fades the level of water inside the vessel rišeš,

- eventually, the flame extinguishes and white smoke appears,

- after the flame is extinguished the level of water inside the vessel rišeš faster...

Each of these observations is the basis for posing a question:

Why does the flame extinguish?

Why does the level of vvater rise?

What parameters are influencing the experimental results?

What is the reproducibility of the experimental results?

What would be the correct chemical equation for this experiment?

Obviously, the number of questions is proportional to the number of observations. It is the task of the teacher to

ask questions in such a way that enables the students to provide an answer based on previously acquired knowledge.

During this process the students must operate at the level of application which requires the development of mental

models to vvhich they usually have little prior exposure. In order to enhance student achievements, the questions used

should be related to mental processes such as application, analysis, synthesis, evaluation and convergent and

divergent production (Anderson et al., 2001; Tisher, 1971). Usually, two or more explanations of the experiment are

offered and this makes an excellent opportunity to confront opinions and challenge the ideas behind. After

exhausting ali the logical arguments, the explanations adopt the form of hypotheses:

Hl) A/iwatCT |cve| depends on the candle height.

H2) A/^er ̂ i depends on the candle diameter.

H3) A/igrate, icvci depends on the properties of liquid.

H4) Flame extinguishes because of complete oxygen depletion.

Hypotheses should be tested and this is usually done by performing well-designed experiments in which a set of

selected parameters is carefully controlled. Designing the experiment will bring out various problems that should be

addressed:

Hovv exactly should an experiment or a measurement be performed?

How many experiments or measurements should be done?

What exactly should be addresed, e.g. what is meant by the term liquid level change?

Hovv much time should pass between successive measurements?

And many more questions depending on the goals of the task.

The interdisciplinarity is introduced by drawing mathematical relationships between different parameters. An

example is the relationship betvveen the change in volume of air vvithin the glass vessel and the change in the level of

the liquid. The concept of calibration should also be invoked and is, indeed, indispensable when using vessels of

conical or irregular shape. Repeated measurements introduce the students to concepts of data reproducibility and

standard deviation. To shorten the time, hypotheses Hl, H2 and H3 can ali be tested as a part of an organised

homevvork task. Students are divided into groups, each with their own set of equipment, and instructed how to

15

perform the experiment in order to minimise the spread of the results. Al i equipment sets contain identical glass

vessels, equal amounts of a l iquid and pans of same diameter and depth. The only differences between sets are the

height and diameter of the candle and the acidity of the liquid. Students are required to collect data before the next

class and mail it to the teacher. A typical set of experimental data is presented in Table l.

Table 1. Typical set of data obtained for different types of candles burning under the glass vessel with three liquidsof distinctive acidity. Data are reported as A/7(<r), where AA is the change of the level of the liquid (given inmilimeters and measured from the boltom of the pan to the edge of the liquid in the glass vessel) and a is thestandard deviation obtained vvith 30 measurements.

p H = 2

pH = 7p H = 9

Small diameter

9.8(0.9)11.8(1.4)

13.8(0.7)

Large diameter

14.3(1.3)

15.8(0.7)

17.8(1.7)

Tali candle

14.3(1.3)

15.8(0.7)

17.8(1.7)

Short candle

19.9(0.5)

20.4(0.6)

22.8(1.1)

It is evident that the pH of the liquid, the diameter of the candle and the height of the candle ali affect the

experimental result. The results obtained by teams of Students unambiguously show that the outcome of the

experiment is strongly dependent on the experimental procedure and that it cannot be used to assess the percentage

of oxygen in air. This is clearly demonstrated by conducting the experiment in a closed system: the candle could be

lit repeatedly, demonstrating that flame exhaustion is related to factors other than complete depletion of oxygen.

Conclusion

One of the basic topics in science teaching should be the relationship and the relevance of science to cultural and

societal development. But, the reality of classroom practice is different: in the majority of cases the teaching is

predominantly instructional (deductive, top-to-bottom approach), i.e. the teachers present the concepts, their logical

implications and provide examples of applications. As a result, Students develop a vvrong perception of science as a

rigid system of trivial facts that should be memorized. In contrast, the SGDBLS teaching method demonstrates

science as a creative, dynamic, intellectually and emotionally involving endeavour in vvhich everyone can participate.

The burning candle experiment should be used in teaching chemistry because it is inexpensive, simple and, if

properly used, is of extremely high educational value. Through this experiment the students are faced with a real and

interdisciplinary scientific problem. To solve it, they are urged to use the physical and chemical concepts they have

acquired so far, discuss the facts, confront ideas and discard them on the basis of facts, in that way becoming trained

in the scientific method.

References

Benneth, J. (2010) Making a difference: factors that affect young people's interesi and participation in science, Book

of Abstracts, 10?h European Conference on Research in Chemical Education, Pedagogical University of

Krakow, Institule of Biology, Departmenl of Chemistry and Chemistry Education, p lO.

Judaš, N. (2010). A postcard from Croatia: VVhere do \ve want to proceed vvith chemical education, Jorunal of

Chemical Education, 87, 250-251.

16

Birk, J. P.; Lavvson, A. E. (1999). The Persistence of the Candle-and-Cylinder Misconception, Jorunal of Chemical

Education, 16, 914-916.

Kmel, D.; Gložar, S. A. (2001). "Experiment with a candle" without a candle, Jorunal of Chemical Education, 78,

914.

Peckham, G. D. (1993). A New Use for the Candle and Tumbler Myth, Jorunal of Chemical Education, 1993, 70,

1008-1009.

\Viederholt E.; Plempel, M. (1996). Gegen den Kerzenversuch zur SaUerstoffbestimmung der Luft, Chemie in der

Schule, 43, 279-283.

MacNeil, J.; Volaric, L. (2003). Incomplete combustion with candle flames: A guided-Inquiry experiment in the

first-year chemistry lab, Jorunal of Chemical Education, 80, 302-304.

Tisher, R. P. (1971). Verbal Interaction in Science Classes, Journal of Research in Science Teaching, 8, 1-8.

Anderson, L. W.; Krathwohl, D. R. (2001). A Taxonomy for learning, Teaching, and Assessing: A Revision of

Bloom's Taxonomy of Educational Objectives, Boston, MA, USA: Allyn & Bacon (Pearson Education Group).

Microscale and Green Chemistry along the years

Mordechai Livneh

Bar-ilan University Ramat-Gan, ISRAEL, livnehm(5);mail.biu.ac.il

There are four general explicit laboratory goals that we want to achieve in laboratory courses:

1. To enable the students to have contact with the materials, to carry out experiments, to make observations

and then discuss and explain the results (In short; observation and discussion).

2. To give the student a feel of the reality of science by an encounter with phenomena that othenvise might

mean no more than just vvords (in short: Actuality).

3. To make the fact of science easy enough to leam and impressive enough to remember.

4. To give the student some insight into basic scientific laboratory methods, and to train him/her in their use

with with a hands-on approach (in short: practice in methods/techniques/instruments)

In short vve can summarize these goals as:

1. Observation and discussion

2. Practice in methods/techniques/instruments

3. Actuality

17

It is extremely important that a specific lab course be aimed at the relevant group of learners. Ali the goals

mentioned here are aimed at undergraduate chemistry majors. For non chemistry majors or high school students, it

may be enough to concentrate on goals l and 3. Nevertheless, sometimes a fevv elements of practice should be

offered to these students too. Students usually like to perform on their own in the lab and hands-on experience is

essential to any scientific subject (but perhaps not in in Mathematics).

Now let's ask ourselves what had happened in the educational laboratories during the last two decades. It is clear

that methods and techniques have constantly changed with time but the goals are still the same. So how is this

reflected in modern laboratories? And what can we expect and plan for the coming years in this branch of science

education?

As the coordinator of the undergraduate labs at BIU for many years I can defmitely notice that two modem

approaches were (and still are) slowly being incorporated into the educational laboratories for ali ages and groups of

learners. The two approaches which are complimentary are:

1. The microscale (small-scale) laboratory.

2. Green chemistry and environmental experiments

The microscale (small-scale) approach

Microscale chemistry means \vorking with quantities of 50-200 mg. and such small quantities demand the

appropriate reduced siže glassvvare and plasticware.

Microscale experiments in chemistry have become popular in science education since the eighties of last

century (although they were originally at the beginning of the thirties). Initially it had started in colleges and

universities but then rapidly spread to primary and high schools and sometimes to to kindergardens too.

Nowdays "Microscale experimentation" has spread worldwide spread and international. Many chemistry and

science educators of ali levels are devoted to elaborating this concept in their respective countries.

Why microscale and why now? A lot of this has to do with the follovving three key items:

A. The electronic balance

B. The stirring hot plate

C. The automatic delivery pipettes.

The benefits of \vorking with microscale amounts and the appropriate apparatus are numerous:

l. Laboratory explosions or fire largely eliminated.

18

2. Reduction of students' contact with toxic materials.

3. Large decrease in waste disposal problems.

4. Economy in cost of materials.

5. Economy of time, space, and energy.

6. Greater discipline, care and cleanliness.

7. A definite impact on the attitude of the student towards the laboratory and making the student more avvare of

society-science-environment relations.

The (new) microscale approach was developed first in relation to organic chemistry. This is obvious since the

major benefits of microscale experimentation is most relevant to organic materials. These materials are usually

combustable, smeli bad, are toxic and are often very costly. Thus people begqan to think about changing the

undergraduate labs to microscale. Two parallel approaches on the matter were simultaneously introduced in the USA

by two groups: The first group čame from Bovvdin College, Maine USA and the second one from Mount Holyoke

College, Massachusetts, USA. Two introductory books for the organic chemistry basic labs were published entitled:

"Microscale Organic Laboratory" (Mayo, Pike and Trumper) ' and "Macroscale and Microscale Organic

Experiments" (Williamson)2. These books are accompanied by kits that were (and are) produced by quite famous

glassware companies, e.g., "Ace Glass" and "Kontess". Later on more books \vere published and more kits were

produced internationally. Thus from organic chemistry the "microscale" approach spread also to inorganic and

general chemistry laboratory courses3. At the same time the microscale approach was adopted by high school

chemistry teachers and today it is well established in many countries of vvhich Israel is a good example4.

In order to find out the popularity of the microscale approach one should refer to the following resources:

1. Books and Kits

2. Publications/Journals or Online

3. Websites, Conferences and International Cooperation.

A variety of vvritten and on-line resources largely exist and in addition to specific conferences that are

dedicated to the subject, one can find many microscale chemistry sessions in almost in any conference on chemical

education.

Examples and Demonstrations of Microscale Experiments

A few examples of short microscale experiments wi l l be mentioned and presented during the talk and a full

\vorkshop will be conducted under the guidance of prof. Melodija Najdoski from the Republic of Macedonia

Green Chemistry

19

Green Chemistry means: "Preventing pollution before it happens rather than cleaning up the mess later". The

green chemistry approach fits well the microscale approach and both approaches have common principles and

attributes. One of the mottos of green chemistry is: "Nowdays what one does not produce from a chemical

reaction is almost as important as what one produce"

An an example, the industrial synthesis of Ibuprofen (ADVIL) vvas done in the 60's in 6 reaction steps and

with 40 % atom economy5 (% atom economy6 = the šum of the molar masses of ali products divided by the šum of

the molar masses of ali the reactants multiplied by 100). In 1991 a nevv synthesis was patented and since then it takes

only 3 steps and the atom economy is 77 %.

CH3

Ibuprofen

Since "Green chemistry" has lately became very important from the industrial point of view it is reasonable

that it should also be reflected/mentioned/experimented in the high-schools and undergraduate laboratory systems

too.

At the beginning, green Chemistry was complementary to the microscale chemistry as working vvith small

quantities is naturally very "Green". However lately green chemistry has quick!y developed into a full discipline in

itself.

References (selected)

1. D.W. Mayo, R.M. Pike and P.K. Trumper, Microscale Organic Laboratory, 4lh edition, John Wiley and Sons

Ine New York, 2000

2. K.L. Williamson, Macroscale and Microscale Organic Experiments, D. C. Heath and Company, Toronto, 1989

3. M.M.Singh, R.M. Pike and Z. Szafran, Microscale and Selected Macroscale Experiments for General and

Advanced General Chemistry, John Wiley and Sons Ine New York, 1995

4. M. Hugerat, P. Schwarz and M. Livneh, Macroscale Experimentation for ali ages, The Academic Arab College

for education , 2006

5. B. M. Trost, Science. 254 (1991) 1471

6. M. C. Cann and M.E. Conelly, Real-World Cases in Green Chemistry, American Chemical Society, 1998, 19-

24.

20

WOORKSHOPS

Selected Microscale Experiments That Provoke Student Curiosity

Metodija Najdoski

Sts. Cyril and Methodius University, Skopje, Republic of Macedonia, e-mail: metonajd@iunona.pmf.ukim.edu.mk

In contrast to the other sciences, the unique nature of chemistry provokes interesi, excitement, and a thirst

for knowledge. The application of experiments in chemistry can also be a powerful tool in maintaining the attention

of the students.

Chemistry teachers have a variety of choices regarding experimentation. They can demonstrate experiments

themselves; they can show videos of experiments, and they can also organize hands-on experimentation for small

groups of students. Al i of these methods should be offered proportionally to the students. The experiments should be

performed in the function of lecture conducting inquiry method.

Experimentation is sometimes not possible during chemistry lectures as there may not be sufficient equipment or

chemical materials avai lable, there is no laboratory, there is not sufficient time, there is no laboratory assistant,

practical work is hazardous, and safety regulations inhibit practical work. The teacher may also feel inadequately

prepared or lacks in experience. Most of these problems can be solved by the introduction of microscale chemistry

experimentation.

To solve some of these problems we čame up with the idea of disposable chemistry kits. During the vvorkshop some

of the chemistry kits for hands-on experimentation will be presented and used by the participants.

The modification of the demonstration of crystallization from a supersaturated solution of sodium acetate

will be presented as crystallization in a plastic ampoule. The process of crystallization begins by opening an ampoule

with scissors. This experiment will be presented in one more modification - a grovving microscale stalagmite.

Experiments: Carbon dioxide cannon, reaction of anhydrous copper(II) sulfate with water, catalytic

oxidation of aluminum and an experiment about hydrolysis will be presented with a help of disposable chemistry

kits. In these experiments the chemistry teachers will have an opportunity to play with the carbon dioxide cannon and

to observe the grovrth of the corrosion product from the aluminum surface, etc.

This workshop is aimed at presenting different angles and point of vievvs in microscale experimental

techniques. In that order, a few microscale methods for gas generation will be presented. One of them will be

presented with a demonstration of an experiment of a photocatalytic reaction of hydrogen with chlorine. Another

method will be presented with the experimental determination of the oxygen content in the air. This experiment will

be carried out in a plastic pipette. This method is based on volume change due to the reaction between NO and

oxygen and the dissolution of the product. For measuring purposes syringes will be used.

Another attractive experiment is that of electrolvsis on a piece paper. After soaking filter paper with an

appropriate solution, one can write or draw on it with an iron nail that is connected to a battery.

21

During the workshop some of the experiments vv i l l be demonstrated and some w i l l be performed by the

participants as hands-on experiments. Most of the experiments vvill be attractive for both elementarv and high school

professors and students.

Put do ravnoteže

Petar Vrkljan

E-škola kemije, Zagreb, Hrvatska

Moguće je nekom zahtjevu udovoljiti na različite načine. No, jesu li svi pristupi dobri? Koji je način najbolji?

Učenje o kemijskoj, dinamičkoj, ravnoteži sasvim je izvjesno težak zadatak za učenika, a još veći izazov za

vrijednog nastavnika.

Stoje moguće učiniti?

Jedna je od mogućnosti da postavimo definiciju stanja ravnoteže i LeChatelierovog načela, a zatim na primjerima

pokazujemo što jest ili nije sustav u stanju ravnoteže. Pokusi u takvoj nastavi služe da potkrijepe izložene tvrdnje.

Takva je praksa danas uobičajena.

Drugi, sasvim izvjesno bolji načinje istraživački miniprojekt gdje nema dociranja, ali ima samovrednovanja. To je

vježba u znanstvenoj metodi. Učenik sam na temelju eksperimentalnog rada, uz pažljivu i poticajnu pmoć

nastavnika, dolazi do spoznaje o za njega novim pojmovima. Takva nastava u Hrvatskoj nije dovoljno raširena, iako

ima lijepu tradiciju.

Imamo li problem?

Potrebno je da učenici dođu do nekih bitnih spoznaja prirodnih znanosti, a to su zakoni prirode i priroda zakona.

U ovom miniprojektu, u kojem je jedan od ciljeva naučiti učenike što je kemijska ravnoteža i kako je na nju moguće

djelovati, prvi je ključni pojam - pojam sustava. Stoje sustav?

Za potrebe ovih istraživanja uzet ćemo da su sadržaji mjehura detergenta, epruveta, ampula, tikvica... sustavi. Ostalo

nas se neće ticati i nazvat ćemo to okolinom. Time smo proizvoljno izabrali dio svemira kojeg smatramo važnim za

istraživanje.

Do te spoznaje učenik treba doći na temelju pokusa.

(Zanima li ga što se događa s epruvetom ili otopinom koja je u njoj?)

Sljedeće pitanje odnosi se na izmjenu tvari i energije sustava s okolinom iz čega slijedi da sustav može biti izoliran,

zatvoren i otvoren.

Što su makroveličine i koja im je uloga u razumijevanju ravnoteže?

Što su intenzivne, a što ekstenzivne fizičke veličine?

Kakva je njihova uloga u utjecaju na ravnotežu?

Sve su to pitanja na koja učenici moraju naučiti odgovoriti, ali sasvim izvjesno ne tako da im odgovore neposredno

prenesemo.

22

Do odgovora učenici u načelu dolaze sami. Naša je uloga u organizaciji istraživačkog miniprojekta, i u pažljivom i

poticajnom vođenju učenika do shvaćanja za njega novih pojmova.

Koji su to novi pojmovi?

Sustav

U prvom pokusu to je praskavac, ali ne i mjehurići detergenta u kojima je praskavac zarobljen, a pogotovo to nije

posudica u kojoj je detergent. Nas zanima samo što se događa s praskavcem (zbunjujuće djeluje činjenica da su

mjehurići nužni da jedno vrijeme zadrže praskavac, ali nas ne zanima što će s njima biti!). U drugom i trećem pokusu

to su otopine indikatora. Epruvete u kojima su indikatori nisu dio istraživanog sustava, jer nas ne zanima što se

eventualno može s njima dogoditi u ovom pokusu. U četvrtom pokusu to je smjesa plinova NO2 i N2O4. Ampula u

kojoj su sadržani nije dio sustava.

U petom pokusu samo je plamen svijeće proučavani sustav. Fitil j i parafin su okolina. U nekom drugom pokusu

svijeća kao takva može biti predmet istraživanja, pa je u tom slučaju ona sustav. U šestom pokusu voda u čašama lb

i 2b je sustav, a same čaše okolina.

U sedmom pokusu sustav čine dušikovi oksidi, kisik i voda u tikvici, jer je za odgovor na pitanje što se događa važno

da se NO2 otapa u vodi.

Izmjena tvari i energije s okolinom

Koliko uopće ima mogućnosti?

Jedna je da sustav s okolinom izmjenjuje i tvar i energiju s okolinom, a druga da ne izmjenjuje ni tvar ni energiju.

Treća je da izmjenjuje samo energiju (ako izmjenjuje tvar, onda izmjenjuje i energiju).

Prvi ćemo sustav nazvati izoliranim, drugi otvorenim, a treći zatvorenim.

Neće biti lako dovesti učenike do spoznaj daje stanje ravnoteže samo u izoliranom sustavu. Tim više što on jasno

vidi da otopina u epruveti nije doslovce izolirana! Al i ! Za potrebe ovog pokusa sve stoje izvan ove ograde smatra se

nevažnim.

Makroveličine

Nabrojimo neke:

Volumen, masa, toplina, množina, gustoća, tlak, temperatura, koncentracija, vrijeme, brzina...

Kada je sustav u stanju ravnoteže nema promjena makroveličina.

Utjecaj na ravnotežu

Razlikujemo ekstenzivne i intenzivne veličine. Intenzivne veličine ne ovise o veličini sustava, a ekstenzivne ovise.

Učenika primjerice treba dovesti do spoznaje da se samo promjenom koncentracije može utjecati na ravnotežu u

vodenoj otopini, a ne samo pormjenom množine. Sama promjena volumena u reakciji plinova ne bi izazvala pomak

ravnoteže da nije došlo i do promjene tlaka. Promjena temperature, a ne izmjena topline uzork je promjeni boje u

ampuli s dušikovim oksidima.

Pokusi moraju biti planirani tako da učenik može dokučiti je li uzrok promjeni intenzivna veličina.

Za tumačenje utjecaja temperature potreban je opis dodatnih pokusa.

23

PLENARV LECTURES

Upgrading Chemistry Teachers' Professional Expertise:

Authentic Learning Communitics

Onno De Jong

Karlstad University, Svveden, o.dejong@uu.nl: onno.deiongtgjkau.se

Teachers are the key actors in the process of implementing innovations in chemistry education. This process requires

the upgrading of teachers' expertise, not only their knowledge base but also their belief system and their skill

repertoire. For instance, chemistry teachers should acquire knowledge of new curriculum topics and how to teach

them. But they also should develop opinions about the value and aim of modern chemistry teaching such as context-

based teaching and computer-assisted instruction. Finally, chemistry teachers should master new skills such as the

competence to coach (not prescribe) students' activities and to design digital learning materials.

Hovvever, several serious difficulties in the upgrading of expertise can be indicated. For instance, many teachers

show resistance to accepting new guiding roles and complain about lack of time for learning to understand new

curriculum topics. Moreover, many teacher training courses show a gap betvveen course 'theory' and classroom

teaching 'practice'. As a consequence, the impact of teacher vvorkshops is often washed out in school practices.

In the present lecture, an important response to these difficulties is addressed: Authentic Learning Communities.

Authentic learning is defined as learning in the vvorkplace and reflecting on it. Communities are defined as netvvorks

of practitioners: groups of teachers, groups of teachers and teacher educators, etc.

In the lecture, special attention is given to an important tool for promoting authentic learning: the use of the Critical

Incident Method (cf. De Jong, 2009). The focus is also on two examples of joint working in Authentic Learning

Communities: (i) an innovative course in scaffolding students in open-inquiry learning (cf. Van der Valk & De Jong,

2009), and, (ii) an innovative course in teaching & designing new context-based units (cf. Stolk, Bulte, De Jong, &

Pilot, 2011). Their contribution to the upgrading of chemistry teachers' professional expertise is discussed.

References

De Jong, O. (2009). Supporting innovations in chemistry teacher education: the Critical Incident Method. In M.

Bilek (Ed.). Research, Theory and Practice in Chemistry Education (pp. 342-352). FIradec Kralove:

Gaudeamus Publishers.

Stolk, M. J., Bulte, A. M. W., De Jong, O., & Pilot, A. (2011). Empovvering chemistry teachers for context-based

designing: a framework for professional development in curriculum innovation. International Journal of

Science Education, (under revision).

U posudu s vodom koja je na temperaturi od recimo 20 °C stavimo tri ti jela jednake mase: od željeza, od a lumini ja i

od olova. Zagrijemo vodu do sto stupnjeva. Pripremimo tri posude s vodom jednakog volumena i temperature. U

svaku uronimo jedno od tri tijela. Uronimo termometre. Temperature vode nisu jednake iako je izmijenjena toplina

jednaka.

U pokusu 4 svaka grupa ima po tri jednake ampule s NO2 i N2O4. Po boji se vidi daje sastav jednak. Iz jednadžbe Q

= m • cp • At slijedi daje At = — — .m-cf

Bitna je dakle razlika u temperaturi.

Pokus l

Eksplozija praskavca (demonstracioni pokus)

Pribor

Uređaj za proizvodnju praskavca elektrolizom

(željezne elektrode uronjene u natrijevu lužinu)

Izvor struje

(20 A, 10 V)

porculanska zdjelica

detergent

šibice

Opis pokusa

Kroz uređaj se preko ispravljača pusti struja. Nastali plinovi uvode se pomoću cijevi u detergent koji je u

porculanskoj zdjelici. Cijev je potrebno odmaknuti čim nastane dovoljno mjehurića. Na mjehuriće bacimo šibicu.

Pitanja

- Zašto su nastali mjehurići (što znače mjehurići)?

- Ima li promjena makro veličina?

- Što je ovdje sustav:

je li to smjesa plinova?

je li to smjesa plinova i detergent?

je li to smjesa plinova, detergent i posuda?

- Ako je praskavac proučavani sustav ima li izmjene tvari i energije s okolinom?

- Ako uklonimo razlog eksploziji praskavca, možemo li opet dobiti praskavac?

Pokus 2

24

Boja fenolftaleina (rad u skupinama)

Pribor

5 stalaka

5 epruveta

5 čaša 250 mL (mogu biti prozirne plastične)

Kemikalije

5 x 30 mL fenolftaleina

5 x 3 0 m L O , l M HC1

5 x 3 0 m L O , l MNaOH

5 x 100 mL dest. vode

Ulijte 2-3 kapi fenolftaleina u epruvetu. Ulijte 2-3 kapi NaOH u otopinu fenolftaleina. Ukapajte HC1 do promjene

boje. Nastavite naizmjenično dodavati NaOH i HC1. Do kada možemo naizmjence dodavati lužinu i kiselinu da se

boja stalno mijenja? Sadržaj epruvete prelijte u čašu i nalijte vodu. Možemo li promijeniti ljubičastu boju (u

bezbojno) bez dodavanja kiseline? Je li promijenjena množina kiseline u otopini dodavanjem vode? Ako nije, stoje

promijenjeno? Je li otopina fenolftaleina sustav u kojem ima promjena makro veličina? Je li otopina fenolftaleina

izmjenjuje tvari i energiju s okolinom? Kada je boja fenolftaleina promijenjena (dodavanjem lužine), možemo li

vratiti sustav u početno stanje ako uklonimo uzrok promjene?

Pokus 3

Boja metiloranža (rad u skupinama)

vidi pokus 2

5 epruveta

5 čaša 250 mL

5 x 30 mL metiloranža

Ulijte 2-3 kapi metiloranža u epruvetu. Ulijte 2-3 kapi HC1 u otopinu metiloranža. Dokapajte NaOH do promjene

boje. Nastavite naizmjenično dodavati HC1 i NaOH. Stoje u ovom pokusu promatrani sustav? Ima li izmjene tvari i

energije sustava s okolinom? Ima li promjena makro veličina? Dodavanjem kiseline izazvana je izvjesna promjena

(žuto u crveno). Možemo li otopinu vratiti u početno stanje? Ako da, kako? Što znači dodavanje lužine s obzirom na

djelovanje kiseline? Jesmo li smanjili množinu kiseline dodavanjem vode? Zašto je boja promijenjena dodatkom

vode?

25

Pokus 4

Dušikovi oksidi (rad u skupinama)

Pribor

5 x 3 ampule s NO2 i N2O4

5 x 2 čaše od 250 mL

kuhalo za vodu

2 - 3 kg leda

l kg kuhinjske soli

krpa, čekić

Prirediti hladnu smjesu u jednoj čaši stavljanjem naizmjence sloj smrvljenog leda i sloj soli. Uroniti u smjesu

ampulu. U drugu čašu uliti vruću vodu iz kuhala. Uroniti u vodu drugu ampulu. Treća ampula na stolu služi za

usporedbu.

Opišite opaženo!

(sadržaj ampule uronjene u hladnu smjesu izblijedio je, a nastalo je i malo plave tekućine; smjesa plinova u ampuli

uronjenoj u vruću vodu potamnila je)

Izvadimo ampule iz hladne smjese i vruće vode i stavimo ih kraj referentne ampule (nakon nekog vremena boja u sve

tri ampule je jednaka). Što je u ovom pokusu istraživani sustav? Ampula s NO2 i N2O4? Čaša s ledom (ili vodom) i

ampula s plinovima? NO2 i N2O4? Ima li izmjene energije i tvari sustava i okoline? Ima li promjena makro veličina?

Je li se sustav vratio u početno stanje nakon što je uklonjen uzrok promjene? Što je uzrok promjene boje? Izmjena

topline? Promjena temperature? Je li viša temperatura plamena šibice ili daske od koje je šibica napravljena? Je li

temperatura plamena jednaka? Možemo li skuhati jaje na plamenu šibice? A na plamenu daske? Što sadrži više

energije: visoka peć u Sisku ili ledenjak na Grenlandu? Vidi opis pokusa u uvodu.

Pokus 5

Plamen svijeće (rad u skupinama)

Pribor

5 svijeća

5 kartona

5 kutija šibica

Postupak

Upalite svijeću. Pričekajte časak, dva. Lagano puhnite prema plamenu i l i mahnite rukom. Zapišite opažanja. Uslijed

puhanja ili mahanja plament zatitra, ali se opet smiri nakon prestanka smetnje. Ima li izmjene tvari i/il i energije s

26

okolinom? Ima li promjena makroveličina? Je li se sustav (plamen svijeće) vratio u početno stanje nakon što je

uklonjen uzrok promjene?

Pokus 6

Vodokotlić (rad u skupinama)

5 x 3 prozirne plastične čaše

5 posuda od oko 600 mL

voda

1. pokus

Iz čaše l a probušene na dnu teče voda u čašu lb i iz nje izlazi kroz jednako veliki otvor sa strane. Razina vode u čaši

lb stalno je jednaka.

2. pokus

Iz čaše 2a probušene na dnu na dva mjesta teče voda u čašu 2b i iz nje izlazi kroz otvor sa strane. Razina vode u čaši

2b je povećana, sve dok čaša 2a nije zamijenjena čašom l a.

Zanimaju nas događaji u čašama b. Je li voda u čaši b izolirani sustav? Ima li promjena makro veličina? Vraća li se

sustav u početno stanje kada uklonimo uzrok promjene?

Pokus 7

Smeđa boca (demonstracijski pokus)

(preparacija i svojstva dušikovog(II) oksida)

Bezbojni plin pripremljen je reakcijom bakra s dušičnom kiselinom i prikupljen u tikvici ispod vode u pneumatskoj

kadi. Kada tikvicu otčepimo nastaje u njoj smeđi plin. Tikvicu, koja sadrži i malo vode, začepimo, potresemo i

smeđa boja nestane. Postupak možemo više puta ponoviti.

Pribor i kemikalije

3,5 g bakrenih pločica

25 mL 8,0 M HNO3 (50 mL konc. HNO3 u 40 mL vode i razrijediti vodom do 100 mL)

bocasisaljka 100 mL

probušeni čep s lijevkom

gumena i l i plastična cijev (50 cm)

staklena cjevčica

27

t ikvica s dugim vratom i okruglim dnom 250 mL

čep

pneumatska kada

Pripremite aparaturu prema skici. Stavite bakar u bocu sisaljku. Zatvorite čepom kroz koji je provučen lijevak.

Napunite t ikvicu s okruglim dnom do vrha s vodom i uronite ju pod vodu u pneumatskoj kadi. Pripremite čep. Ulijte

dušičnu kisel inu kroz lijevak na bakar. NO i O2 u boci daju NO2 smeđe boje. Nakon nekoliko časaka NO će potisnuti

NO2 i O2 iz boce. Tada cijev uvedite u tikvicu i pričekajte dok gotovo sva voda ne bude istisnuta. Potrebno je

povremeno dodavati HNO3 i potresati bocu. Tikvicu začepite pod vodom kada je u njoj zaostalo otprilike 10 mL

vode. Zaustavite reakciju u boci tako da ju ispunite vodom.

Pokažite začepljenu bocu auditoriju. Iza tikvice stavite bijelu podlogu. Otčepite i nakon otprilike 5 sekundi začepite

bocu. Plin u boci je smeđ. Promućkajte i opet je bezbojan.

Opasnosti

NO2 je vrlo otrovan plin. Iritira dišni sustav i do nekoliko sati nakon inhaliranja. Koncentracija od 100 ppm opasna je

čak i nakon kratkog udisanja, a doza od 250 ppm može biti fatalna. Koncentrirana je dušična kiselina i jaka kiselina i

jaki oksidans. Izaziva teške ozljede kože, a kontakt sa zapaljivim tvarima može izazvati požar. Pare iritiraju dišni

sustav, oči i sluznicu. Prolivenu treba najprije neutralizirati s NaHCO3, a zatim obrisati.

Otpad

Tikvica s okruglim dnom može se spremiti i upotrijebiti više puta s tim da mora biti propisno označena kako je netko

ne bi omaškom otvorio. Nakon uporabe ulije se voda i promućka i tako dobivena razrijeđena HNO3 ispere i baci u

izljev. Bakar se ispere i nakon sušenja spremi.

Zadatak je učenika da otkriju spontanu reakciju u boci za odsisavanje i reakcije u ravnoteži u tikvici.

Prilikom izvođenja svih pokusa bila su postavljena pitanja:

- Je li sustav izoliran?

- Ima li vidljivih promjena makro veličina?

- Je li moguće sustav vratiti u početno stanje ako uklonimo uzrok promjene?

U pokusu l praskavac je izolirani sustav, nema promjena makro veličina, ali sustav nije moguće vratiti u početno

stanje uklanjanjem uzroka eksplozije praskavca:

2 H2(g) + 02(g) -> 2 H20(l); Ar// = -571,6 kJ mol'1

za suprotnu promjenu potrebno je dovesti energiju:

2 H20(l) -> 2 H2(g) + 02(g); A r //= 571,6 kJ moP1

28

U pokusima 2 i 3, ako je primjerice dodavanje kiseline izazvalo promjenu boje, neutralizacijom s lužinom boja je

opet kao u početku. Dodavanjem kiseline povećana je koncentracija oksonijevih iona, a dodatkom lužine ta je

koncentracija smanjena. Ako je dakle povećana koncentracija H,O+ uzrok promjene, onda dodavanjem lužine i l i

vode možemo koncentraciju H3O+ smanjiti, a to znači ukloniti uzrok promjene.

U pokusu 4 smjesa NO2 i N2O4 je izolirani sustav, nema promjena makro veličina, a kada prestanemo grijati i l i

hladiti sustav se vraća u početno stanje

N2O4(g) O 2 N02(g); Ar// = 57,2 kJ mol"'

U pokusima 4 i 5 sustavi nisu izolirani, nema promjena makro veličina, a sustavi se vraćaju u početno stanje kada

uklonimo uzrok promjene.

Usporedbom svih pokusa možemo se uvjeriti u postojanje tri različite vrste sustava.

Otopine indikatora (pokus 2 i 3), smjesa plinova (pokus 4) i smjesa plinova i vode u pokusu 7 imaju zajedničko da su

izolirani sustavi, da nema promjena makro veličina i daje takav sustav moguće vratiti u početno stanje ako se ukloni

uzrok promjene.

Takvi su sustavi u stanju ravnoteže.

Praskavac (pokus 1) i smjesa bakra i dušične kiseline (pokus 7) izolirani su sustavi, nema promjena makro veličina,

ali ih nije moguće vratiti u početno stanje uklanjanjem uzroka promjene.

Navedene promjene (eksplozija praskavca i reakcija bakra s dušičnom kiselinom) nazivamo spontanim promjenama.

Voda u posudi b u pokusu 6 i plamen svijeće u pokusu 5 nisu izolirani sustavi, ali nema promjena makro veličina i

moguće ih je vratiti u početno stanje uklanjanjem uzroka promjene.

Govorimo o stacionarnim stanjima.

Iz pokusa 2, 3, 4 i 7 mogli su se učenici uvjeriti da samo promjena fizičke veličine koja ne ovisi o veličini sustava

(intenzivna veličina) utječe na stanje ravnoteže.

Na istim primjerima moguće je naučiti da se radi o kemijskim reakcijama u ravnoteži. Uvijek imamo reakciju i njoj

suprotnu reakciju. Primjerice:

N2O4(g) « 2 N02(g); Ar// = 57,2 kJ moP1

2 N02(g) O N204(g); V/ = -57,2 kJ mof1

29

Te se dvije reakcije odvijaju istovremeno i jednakom brzinom kada je sustav u stanju ravnoteže. Dakle, uvijek se radi

o dvije reakcije, a jednu od njih možemo potaknuti promjenom neke fizičke veličine - promjenom tlaka,

temperature, koncentracije al i ne i promjenom množine, mase, volumena i topline. Samo promjena intenzivne

veličine može pomaknut ravnotežu.

LeChatelierovo načelo mora biti tako definirano da za svaki sustav možemo predvidjeti kako će se ponašati po

djelovanju izvana.

Analiza rezultata pokusa kaže da ako povećamo vrijednost neke intenzivne veličine, onda se time potiče promjena

(jedna od dvije suprotne) koja ima za posljedicu smanjenje te iste veličine i obrnuto.

Literatura

1. P. Vrkljan, N. Judaš i H. Peter, Istraživački miniprojekt i evaluacija znanja i sposobnosti, XVIII. hrvatski

skup kemičara i kemijskih inženjera, Zagreb, 2003.

2. J. Bronovvski, Porijeklo znanja i imaginacije, Stvarnost, Zagreb.

3. G. Pimentel, R. Spratley, Understanding chemistrv, Holden-Day, Inc., San Francisco, 1971.

4. B. Shakhashiri, Chemical Demonstrations, Vol. 2, The Universitv of Wisconsin Press, Madison, 1985.

5. R. Treptovv, Le Chatelier's Principle, J. Chem. Educ. 57 (1980) 417.

6. H. A. Bent, H. E. Bent, What Do I Remember?, J. Chem. Educ. 57 (1980) 609.

Ciljevi i obrazovni ishodi

Objasniti pojam ravnotežnog stanja kemijskog sustava (kemijske reakcije su u ravnoteži).

Objasniti LeChatelierovo načelo i utjecaj različitih čimbenika na ravnotežne stanje kemijskog sustava (samo

promjene intenzivnih veličina utječu na pomak ravnoteže).

Usporediti rezultate pokusa i prosuditi koliko vrsta sustava možemo razlikovat s obzirom na izmjenu tvari i energije

s okolinom,

s obzirom na

nepromjenjivost makroveličina

i

mogućnnost da se sustav nakon izazvane promjene vrati u početno stanje nakon uklanjanja uzroka promjene.

Predvidjeti pomak ravnoteže.

Prethodna znanja

30

egzotermne i endotermne promjene

kemijski simbolički jezik

agregacijska stanja tvari

otopine

U daljnjem učenju kemije na pojmu ravnoteže i LeChatelierovom načelu temelje se neposredno:

Procijeniti opasnosti i predvidjeti potrebne mjere sigurnosti pri radu s kemikalijama.

Objasniti kemijsku reakciju.

Analizirati opis kemijske promjene.

Objasniti pojmove: mjerodavni reaktant, suvišak reaktanta i iskorištenje kemijske reakcije.

Predvidjeti produkte organskih i anorganskih kemijskih reakcija.

Navesti tipične analitičke probe i napisati odgovarajuće jednadžbe kemijskih reakcija.

Povezati dijagram ovisnosti koncentracije tvari o vremenu s jednadžbom kemijske reakcije i odrediti koja je tvar

mjerodavni reaktant il i napisati izraz za empirijsku konstantu ravnoteže.

Objasniti pojam ionskog produkta vode.

Objasniti pojam pH-vrijednosti.

Definirati pojmove kiselina i baza u okviru BL-teorije.

Objasniti pojam reakcije neutralizacije (BL-teorija).

Objasniti odnos između BL-kiseline i njoj konjugirane BL-baze te zadanoj vrsti odrediti konjugiranu kiselinu ili

bazu.

Objasniti pojam kiselinsko-baznog indikatora.

Objasniti pojam amfoternosti i protumačiti ga u okviru BL-teorije kiselina i baza.

Uz kvantnu kemiju, kinetiku i strukturu, ravnoteža čini kičmu fizikalne kemije, pa i kemije u cjelini.

Kemijska svojstva otopine modre galice

Petar Vrkljan

E-škola kemije, Zagreb, Hrvatska

Otopina modre galice poznata je svim vinogradarima. Znaju da moraju barem dan ranije "plavi kamen" staviti u

jutenu vreću (obješenu na prečku, tako da se nalazi u sredini otopine) i uroniti je u bačvu vode. Modra se galica

dobro, ali sporo otapa u vodi.

Koja su to kemijska načela i/il i pojmovi koje učenici mogu otkriti istraživanjem svojstava otopine modre galice?

31

Nizom pokusa vodimo učenike u gotovo sva područja kemije. Sudionici radionice sami će na kraju zaključiti koja su

to područja:

- otopine

- homogeni i heterogeni sustavi

- interakcija tvari i zračenja

- kemijski simbolički jezik

- vrste kemijskih reakcija

- struktura atoma i molekula

- kemijska ravnoteža

- Br0nsted-Lowryjeva teorija kiselina i baza

- Levvisova teorija kiselina i baza

- koordinacijski spojevi

- konstanta ravnoteže

- kemijska termodinamika

Uvodnih je pokusa sedam. Njihovim izvođenjem i točnim zapažanjima učenici će moći odgovoriti na sljedeća

pitanja:

Koliki je pH otopine modre galice?

Koja je boja otopine nakon dodavanja konc. HC1?

Koja je boja otopine, ako nakon HC1 ulijete vodu?

Koja je boja otopine, ako nakon vode ulijete amonijak?

Koju boju imaju pare joda?

Koju boju ima otopina joda u kloroformu?

Koju boju ima otopina joda u vodenoj otopini kalijeva jodida?

Slijede pokusi 5 - 8 , kako je navedeno u uputi za učenike. Za višu razinu (učenici 3. i 4. razreda gimnazije)

predviđen je nastavak istraživačkog miniprojekta s pitanjima od 1. do 8. s predloženim vremenom (45 min) i

bodovima (42 boda) radi samovrednovanja.

Za nižu razinu (učenici 8., 1. i 2. razreda) predviđena su četiri uvodna pokusa:

1. Koja je boja otopine modre galice nakon dodavanja kuhinjske soli?

2. Koju boju imaju pare joda?

3. Koju boju otopina modre galice ima nakon dodavanja kuhinjske soli?

4. Koju boju ima otopina joda u vodenoj otopini kalijeva jodida?

Nakon pokusa 5 - 8 slijedi dio istraživačkog miniprojekta u kojemu učenici istražuju sve moguće reakcije otopina

Na2SO4, Kl, Pb(NO3)2 i PbCl2.

32

Time su učenici pripremljeni za rješavanje problemskog zadatka u kojemu moraju iznaći sadržaje bočica označenih

A, B, C i D, a to su otopine CuSO„, BaCI2, Kl i Pb(NO3)2.

UPUTE ZA UČENIKE

//min Pokus bodovi

2 l . Što opažate kada u otopinu modre galice dodate kuhinjske soli. Zabilježite opažanje. l

2 2. U zatvorenoj epruveti zagrijan je jod. Zapišite opaženo. l

2 3. Jodu, koji je na dnu epruvete dodajte oko 2 mL kloroforma. Zapišite opaženo. l

2 4. Jodu, koji je na dnu epruvete, dodajte oko 2 mL vodene otopine kalijeva jodida. l

Zapišite opaženo.

8 5. U prvu epruvetu ulijte 8 mL destilirane vode. Dodajte 1,5 mL otopine modre galice, a 2

zatim 1,5 mL otopine kalijeva jodida.

Zabilježite opažanja. 3

3 6. U epruvetu (istu) ulijte 4 mL otopine modre galice. l

Zabilježite opažanja. 3

2 7. U epruvetu (istu) ulijte 1,5 mL kloroforma. l

3 Promućkajte. l

Zabilježite opažanja. 3

2 8. U epruvetu (istu) ulijte 1,5 mL amonijaka. l

Zabilježite opažanje. 2

3 Promućkajte. l

Zabilježite opažanje. 3

5 Zbrojite bodove i ocijenite svoj rad.

Pokus 9

Istražite sve mogućnosti miješanjem sljedećih otopina:

Na2SO4 (aq)

Kl (aq)

Pb(N03)2 (aq)

BaCl2 (aq)

Imate na raspolaganju stalak sa šest epruveta. Više vam ne treba, a manje ne smijem dati. Pomno zabilježite uočene

promjene. Zabilježite i kad niste ništa primijetili !

Pokus 10

Imate na raspolaganju 4 bočice s otopinama označenim A, B, C i D. Te otopine su:

CuSO4 (aq)

33

Van Der Valk, A., & De Jong, O. (2009). Scaffolding science teachers in open-inquiry teaching. International

Journal of Science Education, 31, 829-850.

Constructivist and Information-Processing Models in Teaching and Learning

Bob Bucat

The University of Western Australia, bob.bucat(g),uwa.edu.au

Learning is a complex process and certainly little learning occurs by transmission through vvords from the mind of

the teacher to form a duplicate version in the mind of the students. Learning is non-linear and each student arrives at

different forms of understanding of a concept at different moments from every other student.

In this presentation we will discuss two vievvs of how learning occurs: constructivism (of which there are a range of

models), and information processing. Constructivist models of learning are based on a belief that students actively

attempt to construct sense of their world from their experiences - vvhich includes teacher talk and classroom

activities, as well as their out-of-school experiences. The sense that they construct needs to fit in with their prior

learning, unless they re-conceptualise that prior learning. Implications for the classroom teacher need to take into

account the (variable) prior understandings of the students, as well as conceptions that have been developed from

everyday life away from school. Students' conceptual constructions deserve some value other than dichotomous

correct-wrong evaluation.

At the heart of the information-processing model of learning is the recognition that we ali experience more sensory

inputs that we can deal vvith, and we filter out those that are not recognised as relevant or significant to the

knowledge in our long-term memory. In the sense-making that happens through interaction selected inputs with prior

kno\vledge, in a short-term \vorking space, only a limited number of "bits" of knovvledge can be dealt vvith.

Both of these models try to make sense of the interaction of new experiences with previous learning in the formation

of new understandings. We will discuss the implication of these learning models for desirable teacher behaviour in

the classroom.

Chemists' levels of operation: A New Framework

Bob Bucat

The University of VVestern Australia , bob.bucat(5).uwa.edu.au

Johnstone ( 1 , 2 ) has proposed a triangle ways of operating when discussing or thinking about chemical concepts.

These include (i) avvareness of the macroscopic, observable level of the properties of substances, and of particular

chemical reactions, (ii) the sub-microscopic vvorld requiring imagination of the arrangements and interactions of

BaCI2 (aq)

K l ( a q )

Pb(N03)2 (aq)

ali ne nužno tim redoslijedom. Imate i šest epruveta. Istražite u kojoj bočici je pojedina od navedenih otopina.

UPUTA ZA UČENIKE

tIm i n

2

2

l

l

l

I

l

5

2

2

POKUS l Odredite pH otopine modre galice.

POKUS 2 Što opažate kada u otopinu modre galice ulijete koncentriranu solnu

kiselinu?

POKUS 3 Ulijte vodu. Što opažate

POKUS 4 Ulijte koncentriranu vodenu otopinu amonijaka. Zapišite opažanje.

Koju boju imaju pare joda?

Koju boju ima otopina joda u kloroformu?

Koju boju ima otopina joda u vodenoj otopini kalijeva jodida?

POKUS 5 U prvu epruvetu ulijte 8 mL destilirane vode. Dodajte 1,5 mL vodene

otopine modre galice, a zatim 1,5 mL vodene otopine kalijeva jodida.

Zabilježite opažanja.

POKUS 6 U epruvetu (istu) ulijte 4 mL vodene otopine modre galice.

Zabilježite opažanje.

POKUS 7 U epruvetu (istu) ulijte 1,5 mL kloroforma.

Promućkajte.

Zabilježite opažanja.

POKUS 8 U epruvetu (istu) ulijte 1,5 mL vodene otopine amonijaka.

Zabilježite opažanje.

Promućkajte.

Zabilježite opažanja.

24

bodovi

l

l

l

l

l

l

l

2

3

l

3

l

l

3

l

2

l

3

29

34

t/min bodovi

1. Što nastaje reakcijom Cu2+(aq) i I (aq)?

a) Koja tvar (tvar A) u organskim otapalima ima ljubičastu boju?

b) Napišite jednadžbu kemijske reakcije nastajanja tvari A.

c) Ako je nastala tvar A, koja se druga promjena nužno dogodila?

d) Napišite sumarnu jednadžbu kemijske reakcije.

2. Izračunajte potencijal članka u kojem se događa ta reakcija.

a) Napišite dijagram tog članka.

b) Izračunajte razliku potencijala (napon) tog članka.

c) Je li ta reakcija spontana?

3. Izračunajte Gibbsovu energiju ako je AG = - z F A£.

(F =9,65- l O4 C mol'1)

4. Odgovara li napisana sumarna kemijska jednadžba (Id) opaženom?

a) Predložite objašnjenje razlike opaženog i opisanog kemijskom jednadžbom.

b) Napišite kemijsku jednadžbu u skladu s opaženim.

5. Izračunajte Gibbsovu energiju ako je AG = - R T\nK(Ksp = 10""). Zbrojite -z FA£i -R

TlnK.

6. Napišite kemijsku jednadžbu koja opisuje reakciju nastajanja intenzivne plave boje.

7. Objasnite nestajanje intenzivne plave boje.

8. Objasnite nastajanje žute boje (POKUS 5).

l

2

3

2

2

l

l

3

5

5

3

5

5

l

2

4

l

2

2

2

3

5

5

2

S

5

90 minutes of (free) radical chemistry

Krešimir Molčanov

Ruđer Bošković Institute, Zagreb, Hrvatska, e-mail: kmolcano@irb.hr

Radicals, chemical species with unpaired electrons, are usuallv believed to be very unstable; they can be

prepared only under special conditions and can be studied only using special, very expensive, Instruments. However,

due to their unpaired electron, the radicals have a distinct colour, so their appearance can be detected due to a change

of colour. Although they are usually regarded as harmful, they have a crucial role in biological reactions.

Semiquinone is an especially important radical, which acts as an electron carrier in the majority of

bioenergetic reactions (fermentation, oxidation phosphorilation, photosvnthesis). It is formed by reduction of

quinones or oxidation of hydroquinones in the alkaline solution.

35

Semiquinone radical anion is easily prepared in the alkaline solution. Due to change of colour, it can be

easily seen. Even the reaction mechanism can be deduced only by visual observation: the radical may form either by

oxidation of the hydroquinone by oxygen from air or by some other oxidant vvhich is present in the solution.

Tetrachlorosemiquinone radical is so stable that it can exist in the solid state: it forms a green potassium salt vvhich

can be kept for months.

Several simple reactions, vvhich can be performed in the school laboratory, are described. The substances

required are cheap, easily obtainable and non-toxic: hydroquinone, benzoquinone, tetrachloroquinone, sodium

hydroxide.

1. Introduction

Radicals (or, sometimes, free radicals') are chemical species vvith unpaired electrons. They are mostly

unstable and appear only as short-lived intermediates. A common belief among chemists is that the radicals can be

prepared and stabilised only under a strictly controlled environment and that very sophisticated (and expensive)

Instruments are required for their study.

Hovvever, this is not always true. Nitrogen(II) oxide and nitrogen(IV) oxide are radicals (they have 15 and

23 electrons, respectively), but are easily prepared in any (poorly equipped) school laboratory or even a kitchen. We

breathe vvithout thinking that O2 molecules in their ground state are biradicals, i.e. they have two unpaired electrons.

Some organic radicals can even be crystallised; 2,2'-diphenyl-l-picrylhydrazyl (DPPH), first prepared in 1922 [1], is

today used as a standard in measurements of magnetism. The first stable organic radical, triphenylmethyl, vvhich can

be kept in a bottle for months, was prepared by Moses Gomberg in 1898 [2,3].

If vve ask a question "What are free radicals?", the most likely answer vvould be: they are some terribly

dangerous chemicals which cause cancer and premature ageing; some people might say also that the radicals are an

obscure and sinister political organisation. Actually, most of the people consider the radicals as something rather

malign. The reason is insufficient (chemical) education.

Without radicals, no life vvould exist. Almost ali bioenergetic reactions - respiration and photosvnthesis -

are based on oxido-reduction reactions, almost ali of them comprising a radical intermediate.

Due to their unpaired electrons, the radicals are usually coloured (e.g. nitrongen(IV) oxide is red-brown).

Therefore, their formation should be observable due to colour change. Expensive instruments might not be needed

for observation of the radicals; our eyes may be enough at least in the school laboratorv.

In this paper, several simple reactions of preparation of "free" radicals, easily performed in a school

laboratory, are described. The substances used are cheap, easily obtainable and harmless in the small amounts used

for the experiments.

2. Semiquinone radicals

1 This term dates back to 19th century chemists, vvho distinguished functional groups and the „rest" („root" or„residue") of the molecule, vvhich does not change in chemical reactions. This „rest" vvas referred to as a radical.

36

Ouinones (cyclohexanediones) are a large group of organic compounds vvhose basic skeleton is the quinoid

(cyclohexanedione) ring. There are ortho- (1,2-dione) and /?ara-quinones (1,4-dione), Fig. 1. They act as mild

oxidants in the solution. Functional groups bound to the quinoid ring enhance its oxido-reduction potential, which

may vary between +0.9 and +0.1 V. Reduced form of the quinone is dihydroquinone (hydroquinone), Fig. 2, an

aromatic compound with benzenoid ring.

a) b)

Figure l The basic backbone of a) ort/;o-quinones (1,2-dione) i b)/?ara-quinones (1,4-dione).

H •H

H

a) b)

Figure 2 The basic backbone of a) or//»o-hydroquinones (l,2-dihydroxybenzene) i b) /?ara-hydroquinones (1,4-

dihydroxybenzene).

The transition of quinones into hydroquinones (and vice-versa) can be easily done under mild, even

physiological, conditions. Electron transfer, i.e. oxidation or reduction, is coupled by a proton transfer: the

hydroquionone molecule has to be deprotonated (hydroquinonate dianion). As a short-lived, but nevertheless

relatively stable intermediate, the semiquinone radical is formed (Fig. 3) [4,5,6]. Semiquinoid ring is difficult to

represent by canonical formulae; its unpaired electron is delocalised throughout the entire ring (Fig. 4), vvhich is,

therefore, halfway betvveen a quinoid and an aromatic one. Stability of the radicals is modified by substituents: more

electronegative ones (reducing the electron density in the ring) make the radical more stable. Some can even be

crystallised: sodium and potassium salt of the tetrachlorosemiquinone radical has been known for almost a century

[7].

37

OH

SEMIOUINONERADICAL

OH

+e +2H*

-e- -2H*

BENZOOUINONE SEMIOUINONERADICAL ANION

OH

HVDROOUINONE

Figure 3 Proposed mechanism of redox reactions in the quinone/hydroquinone system, according to [4,5,6].

O

o_

Figure 4 Unpaired electron and negative charge are delocalised throughout the entire semiquinoid ring; some of the

canonical formulae are shown.

Since quinones/hydroquinones are easily reducen/oxidised, they make perfect vehicles for electron transfer

in the biological systems. They participate in a majority of processes of biological importance in vvhich energy is

bound or released, such as photosynthesis and respiration.

Coenzime Q, also known as ubiquinone (Fig. 5), is found in almost ali plants, animals and microorganisms2.

It is found in mitochondria, membranes of endoplasmatic reticulum, lysosomes and a number of organelles vvhose

names end with -som. It participates in the process of oxidation phosphorilation:

CoQH2 + 2Fe'"-cytochrome C -> CoQ + 2Fe"-cytochrome C

The coenzyme CoQ,0 is "responsible" for production of ča. 95 % of energy in the human organism [8].

Therefore its name: lat. ubique - everywhere.

38

H3C-0

H3C—O

Figure 5 The basic backbone of ubiquinones.

Plastoquinone, an ubiquinone-like compound, participates in electron transfer in photosynthetic

photosystem II [9,10]. In ali biological redox-reactions of quinones, the radical intermediate, semiquinone, is formed.

Flavonoids, phenol-like compounds, are found in the green plants, where they play a myriad of diverse

roles: they act as antioxidants, proteci the plants from microbes, insects and UV radiation and serve as

photoreceptors and pigments. Many flavones, such as quercetine and catechine, have an o-dihydroxy phenyl moiety

[12], and therefore may be regarded as o-hydroquinones. Due to their mild reducing properties, their role in the

organism is reduction of harmful free radicals. In their reactions, a radical intermediate, o-semiquinone is formed,

and it is eventually reduced into o-quinone (Fig. 6). The single flavone molecule can reduce two harmful radicals;

the semiquinone radical is relatively stable and therefore harmless [12,13].

OH

Figure 6 Oxidation mechanism of flavonoids with o-hydroquinone moiety: a single flavonoid molecule can reduce

two free radicals.

Many quinones, especially 2,5-dihydroxy-l,4-quinones (anilic acids) are promising candidates for synthesis

of the "functional materials" [14,15] and crystals of exceptional electric and magnetic properties [16,17]; some of

them comprise semiquinone radicals [18,19,20].

3. Experiments

3.1. Quinhydrone

The 1:1 mixture of p-benzoquinone (commonly called quinone) and p-benzohydroquinone (commonly

called hydroquinone), has been known since mid-19th century [5]. It has been used as a standard in electrochemistry

for the last eight decades [4]. It is usually prepared by cocrystallization of equimolar amounts of benzoquinone and

hydroquinone from a solution (aqueous, alcoholic, acetone...), but it can also be prepared by grinding of the solid

39

samples of benzoquinone and hydroquinone. This method, knovvn as the "mechanochemical synthesis" has recently

become a subject of intense study [21,22,23,24].

Note that the hydroquinone is colourless (Fig. 7a), benzoquinone is yellow (Fig. 7b), but the quinhydrone is

dark green (Fig. 7c). We can expect that a mixture of a colourless and a yellow substance should be pale yellow; a

colour change indicates a chemical reaction. What happens here?

The crystal structure of quinhydrone might offer us a clue (Fig. 8): molecules of quinone and hydroquinone

are linked by hydrogen bonds into infinite chains. Charge transfer (electron or proton or both) betvveen quinone and

hydroquinone molecules is possible along the hydrogen bonds; it may also influence the change of colour. However,

no radicals exist in the quinhydrone at atmospheric pressure; their formation can be induced by very high pressure

(1.5-3 GPa) [25,26] or by irradiation of the crystals by X-rays [5,6].

We can simply prove that the partial charge transfer taking part in the quinhydrone is a result of crystal

packing. By dissolution of the quinhydrone in water or acetone the dark green substance produces a pale yellow

solution. Therefore, no charge transfer exists in the solution.

a) b) c)

Figure 7 Crystalline samples of a) hydroquinone, b) benzoquinone i c) quinhydrone.

a)

40

O-H- 0-H-O 0-H---0

b)Figure 8 a) Crystal structure of monoclinic quinhydrone, as determined by Sakurai (1968) [27]: alterrnating quinone

and hydroquinone molecules are hydrogen bonded into infinite chains. Charge transfer (i.e. electron or proton

transfer) is possible along the chains. b) Schematic dravving of a chain with highlighted repeating motive

(asymmetric unit). The figure has been taken from ref. [6].

3.2. Oxidation of hydroquinone in the alkaline solution

It it well known, but often ignored, that the semiquinone radical is stable in an alkaline solution, and that the

hydroquinone in alkaline solution is slowly oxidised into the radical [4,5,6]. In aqueous NaOH or KOH (c = 0.25 - 3

mol dm"3) this reaction takes several minutes (it is faster in more concentrated NaOH), so it can be monitored using

our eyes only. This experiment is easily performed in a school laboratory. The solution is initially colourless (Fig.

9a), but it quickly turns to yellow, and a brovvn layer can be observed on its surface (Fig. 9b). After some time, the

entire solution becomes red-brown, but the colour is still the most intense on the surface (Fig. 9c).

We can conclude that the hydroquinone, which is deprotonated in the alkaline solution (Fig. 3), is oxidised

into semiquinone radical by oxygen from air: the red-brown colour first appears on the surface and is spread through

the solution by diffusion. The radical is red-brown. NaOH or KOH act as catalysts since the neutral hydroquinone

does not react with oxygen. Neutral aqueous solution of the hydroquinone is colourless and no colour change can be

noticed even after standing for several days.

a) b) c)

Figure 9 Oxidation of hydroquinone in the alkaline solution: a) a fresh solution of hydroquinone, b) the same

solution after 10 minutes, c) the same solution after 20 minutes.

3.3 Disproportionation of quinhydrone

41

The aqueous solution of quinhydrone is pale yellow (Fig. lOa). Hovvever, if we add just one drop of NaOH,

the colour will instantly change to red-brown. We can observe that the colour change first occurs where the drop has

touched the solution (Fig. lOb); after several seconds the colour is spread throughout the solution by diffusion (Fig.

l Oc). Apparently, oxygen takes no part in this reaction (since the colour appears suddenly, and not on the surface),

and NaOH again serves as a catalyst. The oxidant (electron acceptor) is benzoquinone, vvhich is reduced into the

semiquinone radical; the hydroquinonate anion is oxidised into the semiquinone radical (Fig. 11).

a) b) c)

Figure 10 Disproportionation of quinhydrone in an alkali solution: a) neutral aqueous solution of quinhydrone, b)

the same solution immediately after a drop of NaOH is added, c) the same solution after l minute.

O + HO 2 O

Figure 11 Scheme of disproportionation of quinhydrone in an alkali solution.

O + 2 H

3.3. Semiquinone radical in the solid state

Tetrachloroquinone (also known as chloranil) is a yellow compound soluble only in acetone (Fig. 12a), and

its solution is yellow. Upon addition of excess of solid sodium or potassium iodide, a green substance will precipitate

and the colour of the solution will turn to red-brown (SI. 12b). The reaction should take 10-15 minutes (Fig. 12c).

After that, the acetone solution is decanted; alcohol and starch are added to it. Blue colour of the solution

indicates presence of I2. In this reaction, iodide ions were oxidised into molecular iodine; the only present oxidant is

tetrachloroquinone, which is reduced into thetrachlorosemiquinone radical anion. Its potassium salt is insoluble in

acetone (Fig. 13).

The green precipitate of alkali tetrachlorosemiquinone radical anion salt readily dissolves in vvater. The

solution is initially green, but after several seconds a yellow precipitate is observed: the radical is green in the

solution, but quickly oxidises into the tetrachloroquinone

42

a) b) c)

Figure 12 Preparation of potassium salt of tetrachlorosemiquinone radical anion: a) acetone solution of

tetrachloroquinone, b) the same solution 10 seconds after addition of solid Kl, c) The same solution after 10 minutes.

Cl. Cl

Cl Cl Cl Cl

Figure 13 Scheme of the reaction of potassium iodide and tetrachloroquinone.

O K+ + 1/2 '2

4. Conclusions

Ali experiments described in this paper can be performed in no more than 90 minutes, and they can provide

us with insights into chemistry of semiquinone radicals. Reaction mechanisms can be deduced only by observation,

no special Instruments are needed.

The free radical \vorkshop is applicable to high school students and university students of chemistry and

related fields. As a part of the project "e-school of chemistrv", a number of workshops for students of 3rd and 4th

grade of high school were held; the students easily performed ali experiments and vvere able to deduce the reaction

mechanisms. Students of the Ist year of chemistry (Faculty of Science, University of Zagreb) performed equally

well.

References

[1] N. D. Vordanov, Appl. Magn. Reson., 10 (1996), 339.

[2] M. Gomberg, J. Am. Chem. Soc., 20 (1898), 773-780.

[3] M. Gomberg, J. Am. Chem. Soc., 22 (1900), 757-771.

[4] B. R. Eggins, J. Q. Chambers, J. Electrochem. Soc., 117 (1970), 186-192.

43

atoms, ions and molecules, and ( i i i ) the need to communicate about either of the previous levels through the use of

language and svmbolism that are peculiar to chemistrv.

Chemistrv experts 'svvitch' unconsciouslv and seamlesslv between these levels, but we should be avvare that students

may not do so and may become confused if \ve teachers do not take pains to explicitly indicate the level at which

each part of a presentation is concerned. This distinction betvveen levels of the triangle has come to be regarded as so

important that many textbooks and computer-based instructional materials are designed with this in mind.

More recently, Jensen (3, 4) has proposed three levels of operation, other than language, that are commonly used by

chemists. He labels these molar (corresponding with Johnstone's macroscopic level), molecular and electronic -

these latter two being sub-sets of Johnstone's submicroscopic level. This paper will integrale the models of

Johnstone and Jensen.

In addition the author recognises another sense in vvhich there are different levels of modelling by chemists:

visualisation of many-particle images of substances at the molecular level vs. visualisation of single-particle images.

Ali of these are brought together to construct a many-layered framework of the modes of operation of chemists.

Some implications of teaching and learning without a consciousness of these layers will be discussed. The

framevvork exposes the complexity of learning chemistry.

References

1. Johnstone, A.H. School Sci. Rev. 1982, 64, 377.

2. Johnstone, A.H. J. Computer Assisted Learning 1991, 7, 75.

3. Jensen, W.B. J. Chem. Educ. 1998, 75, 679.

4. Jensen, W.B. J. Chem. Educ. 1998, 75, 817.

Answers you don't want your students to write on examinations: Examples of student

difficulties and trends on the College Board Advanced Placement Chemistrv Test.

Marian L. DeWane

Boise, Idaho, United States of America, mariandewane(S).u.boisestate.edu

The College Board offers thirty-four Advanced Placement (AP) examinations, including AP Chemistry, that are

administered internationally each May. Students who demonstrate competency can earn college credit. The reading

(grading) of the AP Chemistry exams occurs in June. Each of the 220 readers, high school and college chemistry

faculty,are placed in groups and each group is assigned one question to grade. Approximately 110,000 exams must

be graded in six days. Each exam consists of a multiple-choice question

section and a free response section. The free response section is graded by the readers. Regardless of what country

students are from, students exhibit a range of problem solving abilities and conceptual understanding.

[5] K. Molčanov, Structure abd Dynamics ofHydrogen Bonds in Crystals of Substituted Quinones, Ph.D.

Dissertation, University of Zagreb, 2008.

[6] K. Molčanov, B. Kojić-Prodić, M. Roboz, Ada Cryst. B, 62 (2006), 1051-1060.

[7] H. Torrey, W. H. Hunter, J. Am. Chem. Soc., 34 (1912), 702-716.

[8] Q. Guo, J. T. Corbett, G. Yue, Y. C. Fann, S. Y. Qian, K. B. Tomer, R. P. Mason, J. Biol. Chem., 277 (2002),

6104-6110.

[9] D. R. Kolling, R. I. Samoilova, J. T. Holland, E. A. Berry, S. A. Dikanov, A. R. Crofts,./. Biol. Chem., 278

(2003), 39747-39754.

[10] A. Mezzetti, W. Leibl, Ettr. Biophys. J, 34 (2005), 921-936.

[l 1] A. Osvczka, C. C. Moser, F. Daldal, P. L. Dutton, Nature (London), 427 (2004), 607-612.

[12] 0. M. Andersen, K. R. Markham, Flavonoids: Chemistry, Biochemistry and Applications, CRC Taylor&

Francis, Boca Raton, Fl., SAD, 2006.

[13] P.-G. Pietta, J. Nat. Prod., 63 (2000), 1035-1042.

[14] S. Kitagawa, R. Matsuda, Coord. Chem. Rev., 251 (2007), 2490-2509.

[15] S. Kitagavva, S. Kavvata, Coord. Chem. Rev., 224 (2002), 11-34.

[16] G. R. Desiraju, Angew. Chem., Int. Ed, 46 (2007), 8342-8356.

[17] D. Braga, L. Brammer, N. Champness, CrystEngComm, 7 (2005), 1-19.

[18] M. LeCointe, M. H. Lemee-Cailleau, H. Cailleau, B. Toudic, L. Toupet, G. Heger, F. Moussa, P. Schweiss, K.

H. Kraft, N. Karl, Phys. Rev. B, 51 (1995), 3374-3386.

[19] T. Murata, Y. Morila, Y. Vakizama, K. Fukui, H. Vamochi, G. Saito, K. Nakasuji, J. Am. Chem. Soc., 129

(2002), 10837-10846.

[20] S. Horiuchi, R. Kumai, Y. Tokura, Chem. Comm., 2007, 2231-2329.

[21] N. Shan, F. Toda, W. Jones, Chem. Comm., 2002, 2372-2373.

[22] A. V. Trask, W. D. S. Mothenvell, W. Jones, Chem. Comm., 2004, 890-891.

[23] T. Friščić, L. Fabian, CrystEngComm, 11 (2009), 743-745.

[24] T. Friščić, S. L. Childs, S. A. A. Rizvi, W. Jones, CrystEngComm, 11 (2009), 418-426.

[25] Y. Uchida, C. Okabe, A. Kisni, H. Takeshita, Y. Suzuki, Y. Nibu, R. Shimada, H. Shimada, Buli Chem. Soc.

Jpn., 75 (2002), 695-703.

[26] K. Nakasuji, K. Sugura, T. Kitagawa, Y. Tovoda, H. Okamoto, K. Okanivva, T. Mitani, H. Yamamoto, I.

Murata, A. Kawamoto, J. Tanaka,y. Am. Chem. Soc., 113 (1991), 1862-1864.

[27] T. Sakurai, Acta Cryst. B, 24 (1968), 403-412.

SELECTED PRESENTATIONS

Vanjsko vrjednovanje obrazovnih postignuća učenika iz kemije kao temelj unaprjeđenjakvalitete nastave kemije u osnovnim školama Republike Hrvatske

Nenad Marković, Ivan Vicković, Petar Vrkljan

44

Nacionalni centar za vanjsko vrednovanje obrazovanja, Hrvatska, nenad.markovicfgjncvvo.hr

U Republici Hrvatskoj u zadnjih pet godina započete su i provode se promjene na svim razinama odgojno-

obrazovnoga sustava (Burušić i sur. 2008). Obrazovni sustav izuzetno je važan segment društvenoga funkcioniranja,

a njegova kvaliteta utječe na sva područja društva i na osobni razvoj pojedinca. Unaprjeđenje kvalitete obrazovanja

jedan je od strateških ciljeva Republike Hrvatske i treba biti i zadaćom svake pojedinačne obrazovane institucije

(Muraja 2009). Jedan od bitnih čimbenika koji utječu na poboljšanje kvalitete obrazovnoga sustava je i razvijanje

sustava vanjskoga vrjednovanja u Republici Hrvatskoj. Sustav vanjskoga vrjednovanja u obrazovanju jedan je od

strateških ciljeva našega obrazovanja opisan u dokumentu „ Plan razvoja sustava odgoja i obrazovanja 2005.-

2010." koji je izdalo Ministarstvo znanosti, obrazovanja i športa (2005). Vanjsko vrjednovanje obrazovanja je

mehanizam za objektivno praćenje obrazovnoga sustava u Republici Hrvatskoj, a temelji se na standardiziranim

ispitima koje provodi institucija neovisna o pojedinoj školi, odnosno Nacionalni centar za vanjsko vrednovanje

obrazovanja (u daljnjem tekstu: Centar). Vanjskomu vrjednovanju pripadaju dvije vrste provjere učeničkih

postignuća; nacionalni ispiti kojima se procjenjuju postignuća učenika u tijeku obrazovnoga ciklusa i dobiva uvid u

kvalitetu obrazovnoga sustava i državna matura kojom se provjerava razina dosegnutih znanja, vještina i

kompetencija na kraju školovanja te pokazuje osposobljenost učenika za daljnje školovanje ili tržište rada (Muraja

2009). Centar je započeo s projektima vrjednovanja obrazovanja 2006. godine. Osborne i sur. (2008) u Izvješću

"Prirodoslovno obrazovanje u Europi: Kritički osvrt" podnesenom Nuffield Foundation ističu u šestoj preporuci

sljedeće: „Vlade zemlja EU trebale bi značajno ulagati u istraživanje i razvoj vrjednovanja prirodoslovnoga

obrazovanja. Cilj su konstrukcije ispita i metoda koje provjeravaju vještine, znanje i kompetencije koje se očekuju od

prirodoslovno opismenjenoga građanina. "Kada govorimo o kompetencijama, riječ je o relativno široko definiranim

kategorijama. No kompetencije se mogu prevesti u vrlo konkretne ishode učenja. Drugim riječima postizanjem

odgovarajućih ishoda učenja, učenik dokazuje da je stekao neku kompetenciju (Vizek Vidović 2009). Rezultate

odgojno-obrazovnoga procesa možemo jednim imenom nazvati učeničkim postignućima. Sadržaj, struktura i

primjena tih postignuća ovise o brojnim Činiteljima, među kojima su najvažniji sam program obrazovanja, kvaliteta

rada učitelja, opremljenost i pristupačnost izvorima znanja i sredstvima poučavanja, motiviranost učenika da ta

postignuća steknu itd. (Bežen 2008). Nadalje u dokumentu o NAEP-u (Nacionalnoj procjeni napretka u obrazovanju

u SAD-u) (2005) ističe se da pismenost u području prirodoslovlja predstavlja cilj za sve pripadnike američke

mladeži. U NAEP-u (2005) se zatim ističe da kroz prirodoslovno obrazovanje djeca počinju razumijevati svijet u

kojem žive i uče kako primijeniti znanstvena načela u mnogim aspektima svoga života. U skladu s dokumentima

Vlade Republike Hrvatske i Ministarstva znanosti, obrazovanja i športa (Plan razvoja sustava odgoja i obrazovanja

2005.-2010. (2005), Vodič kroz Hrvatski nacionalni obrazovni standard u osnovnoj školi (2005), Nastavni plan i

program za osnovnu školu (2006) Centar je donio dokument pod nazivom Strategija vanjskog vrjednovanja

obrazovnih postignuća učenika osmih razreda iz predmeta Biologija, Kemija, Fizika, Geografija i Povijest (2008).

Na temelju strategije nacionalnih ispita postavljen je cilj nacionalnih ispita: provjeriti obrazovna postignuća misleći

pri tome na sposobnosti rješavanja problemskih interdisciplinarnih zadataka i kompetencije u učenju istraživanjem i

otkrivanjem te donošenju zaključaka na temelju rezultata istraživanja. U skladu s navedenim činjenicama koncipiran

je jedinstveni ispit koji se sastojao od četiri dijela - Biologija, Kemija, Fizika te Integracijski dio (koji je obuhvaćao

45

sadržaj fizike, kemije i biologije). Tako se približno 25% pitanja odnosilo na nastavne sadržaje iz biologije, 25%

pitanja na nastavne sadržaje iz kemije, 25% pitanja na nastavne sadržaje iz fizike, a preostalih 25% pitanja bilo je

interdisciplinarno. Ispitom iz kemije provjerena su obrazovna postignuća prema postojećem Nastavnom planu i

programu za osnovnu školu (MZOŠ, 2006.) koji je priređen prema HNOS-u (MZOŠ, 2005.). U kontekstu obrazovnih

postignuća ispitom iz kemije se provjeravalo sljedeće: trajnost usvojenih znanja, prirodoslovna i matematička

pismenost, sposobnost rješavanja problemskih interdisciplinarnih zadataka, postignuća u učenju istraživanjem i

otkrivanjem. Završno ispitivanje obrazovnih postignuća iz fizike, biologije i kemije trajalo je sveukupno 115 minuta,

a u njemu je sudjelovalo 21 817 učenika. Sam ispit trajao je 100 minuta i imao jednu stanku od 15 minuta nakon

drugoga dijela ispita. Svi ispiti, koji su primjenjivani u glavnom ispitivanju (testiranju) u školskoj godini 2007/2008.,

standardizirani su u probnom ispitivanju na slučajno odabranom uzorku. Dio ispita koji se odnosio na kemiju trajao

je 30 minuta, a sastojao se od 15 zadataka. U ukupnom broju zadataka, 10 zadataka (l .- 10. zadatka) je bilo

zatvorenoga tipa, višestrukoga izbora (svaki zadatak l bod), a 5 zadataka je bilo otvorenoga tipa - zadatci kratkih

odgovora (11. Zadatak - 2 boda, 12. i 13. Zadatak - 3 boda, 14. zadatak - 2 boda, 15. Zadatak - Ibod). Integracijski

dio ispita trajao je 15 minuta, a sastojao se od 8 pitanja. Prema vrsti zadataka u ovome dijelu ispita 5 zadataka (1.-

5. zadatak) je bilo zatvorenoga tipa, višestrukoga izbora (svaki zadatak l bod), a 3 zadatka su bila otvorenoga tipa-

zadatci kratkih odgovora (6. zadatak- 2 boda, 7. zadatak-1 bod, 8. zadatak - 2 boda). Prema Burušiću i sur. (2008)

rezultati metrijske analize ispita iz kemije pokazale su sljedeće karakteristike ispita: maksimalni broj bodova u

ispitu bio je 21, distribucija rezultata je pokazala da je ispit nešto veće težine, pouzdanost rezultata na ispitu iz

Kemije bila je zadovoljavajuća (Cronbachov a=0,75), ocjena iz kemije u 7.r. i rezultat na ispitu iz kemije koreliraju

(r = 0,46), prosječna riješenost testa 7,54 bodova, prosječni rezultat riješenosti testa je 36%. Prema Burušiću i sur.

(2008). rezultati metrijske analize ispita iz integracije pokazale su sljedeće karakteristike ispita: maksimalni broj

bodova u ispitu bio je 10, distribucija rezultata je pokazala daje ispit nešto veće težine, pouzdanost rezultata na ispitu

iz Integracije bila je niska (Cronbachov a=0,51), prosječna riješenost testa 3,35 bodova, prosječni rezultat riješenosti

testa je 33,50%. Nadalje u suradnji Centra i vanjskih stručnih suradnika (u daljnjem tekstu: suradnici) od

studenoga 2009. do rujna 2010. obavljena je kvalitativna analiza ispita iz kemije i integracije prema sljedećim

odrednicama: odabran je uzorak ispita (N=500), uzorak je analiziran kvantitativno gdje je kombiniran pristup iz

klasične teorije testova i suvremene teorije odgovora na zadatak (Buljan Culej 2009). (metrijska analiza

zadataka), a rezultati su uspoređeni s odgovarajućom kvantitativnom analizom svih ispita (metrijska analiza svih

ispita), načinjena je kognitivna valorizacija ispitnih zadataka prema reduciranoj Bloomovoj taksonomiji (Anderson i

Krathwohl 2001). Pripremljen je reprezentativni uzorak (N=500), iz baze podataka o ispitima svih učenika. Uzorak

je analiziran tako da su istaknuti netočni odgovori, različiti tipovi grješaka, učestali alternativni koncepti te postupci

rješavanja za svaki pojedini zadatak. Rezultati su predočeni dijagramima distribucije uspješnosti u svim zadatcima

(21 zadatak iz područja kemije i 8 iz područja integracije). Drugi važan rezultat slijedi iz analize svih vrsta netočnih

odgovora u zadatcima otvorenoga tipa. U njima ima od 7 do 67 različitih vrsta netočnih odgovora. Centar i suradnici

su temeljem opisane analize i zaključaka donijeli određene preporuke 1. glede eventualne promjena nekih

obrazovnih postignuća u nastavnom planu i programu u OŠ, 2. o načinu poučavanja u nastavi, 3. o edukaciji učitelja i

4. o vanjskom vrjednovanju u budućnosti. Sažetak važnijih zaključaka i preporuka kao prilog unaprjeđenju

kvalitete nastave kemije:!, postojeći nastavni plan i program je dobar, ali su uočene značajne poteškoće u slučaju

46

kada se nastavni sadržaji trebaju korelirati s drugim predmetima, naročito s matematikom (primjerice, to su četiri

osnovne računske operacije), 2. temeljem gore navedene analize uočen je problem rješavanja problemskih i

računskih zadataka te slabo korištenje i poznavanje mjernih jedinica; preporuka je da se u nastavi inzistira na

korištenju i pisanju mjernih jedinica, 3. veliki broj neriješenih zadataka koji uključuju eksperimentiranje u nastavi

kemije upućuje na manjak eksperimentalnoga rada u nastavi kemije, 4. potrebno je organizirati i provesti takva

stručna usavršavanja učitelja kemije u kojima će biti više metodičkih prikaza usvajanja temeljnih znanja i vještina, 5.

potrebno je i nadalje provoditi vanjsko vrjednovanje iz kemije standardiziranim ispitima koji bi ubuduće uključili

više zadataka višestrukoga izbora jer oni dobro diskriminiraju uspješne od neuspješnih učenika, a i lakše ih je

ocijeniti što u konačnici pojeftinjuje ocjenjivanje ispitnih zadataka, 6. važno je temeljem ove analize izraditi načela

za izradbu mjerljivih obrazovnih ishoda (postignuća) koje učenici trebaju ostvariti do kraja 8. razreda iz kemije jer u

postojećem nastavnom planu i programu za osnovnu školu naznačeni su uopćeni obrazovni ishodi (obrazovni

standardi), stoje napredak u odnosu na dokumente koji su mu prethodili.

LITERATURA1. Anderson, L.W., i Krathvvohl, D.R.(Eds.). (2001). A taxonomy for learning, teching and assessing: A

revision ofBloom 's Taxonomy ofeducational objectives: Complete edition. New York: Longman.

2. Bežen, A. (2008). Metodika - znanost o poučavanju nastavnog predmeta. Zagreb: Profil.

3. Buljan Culej, J. (2009). Psihometrijska analiza nacionalnih ispita provedenih u trećim razredima

gimnazijskih i četverogodišnjih strukovnih škola šk. g. 2007./2008. Glavno izvješće. Zagreb: Nacionalni

centar za vanjsko vrednovanje obrazovanja.

4. Burušić, J., Babarović, T., Šakić, M. (2008). Vanjsko vrednovanje obrazovnih postignuća osnovnih škola u

Republici Hrvatskoj; Učenici 8. razreda, školska godina 2007./2008.; Istraživački izvještaj. Zagreb:

Nacionalni centar za vanjsko vrednovanje obrazovanja i Institut društvenih znanosti Ivo Pilar.

5. Developed by West Ed and the Councile of Chief State School OfFicers under contract to the National

Assessment Governing Board (2005). Science Frameworkfor the 2009 National Assessment of Educational

Progress. Science NAEP 2009. Contract# ED04CO0148.

6. Ministarstvo znanosti, obrazovanja i športa (2005). Plan razvoja sustava odgoja i obrazovanja 2005.- 2010.

Zagreb: Ministarstvo znanosti, obrazovanja i športa.

7. Ministarstvo znanosti, obrazovanja i športa (2006). Nastavni plan i program za osnovnu školu. Zagreb:

Ministarstvo znanosti, obrazovanja i športa.

8. Ministarstvo znanosti, obrazovanja i športa (2010). Nacionalni okvirni kurikulum za predškolski odgoj i

obrazovanje te opće obvezno i srednjoškolsko obrazovanje. Zagreb: Ministarstvo znanosti, obrazovanja i

športa.

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9. Ministarstvo znanosti, obrazovanja i športa (2005). Vodič kroz Hrvatski nacionalni obrazovni standard.

Zagreb: Ministarstvo znanosti, obrazovanja i športa.

10. Muraja, J., (ur.) (2009). Vodič za provedbu samovrjednovanja u osnovnim školama. Zagreb: Denona d.o.o.

11. Nacionalni centar za vanjsko vrednovanje obrazovanja (2008). Strategija vanjskog vrjednovanja obrazovnih

postignuća učenika osmih razreda iz predmeta Biologija, Kemija, Fizika, Geografija i Povijest - interno

izvješće. Zagreb: Nacionalni centar za vanjsko vrednovanje obrazovanja.

12. Osborne, J., Dillon, J. (2008). Science Educational in Europe: Critical Reflections. A Report to the Nuffield

Foundation. London: King's College London.

13. Vizek Vidović, V. (2009). Planiranje kurikuluma usmjerenoga na kompetencije u obrazovanju učitelja i

nastavnika. Zagreb: Filozofski fakultet Sveučilišta u Zagrebu.

The Teaching of Chemistry in Croatia - Reflections of an Old Chemistry Teacher

Tomislav Cvitaš

Department ofChemistrv, Faculty of Science, Universitv of Zagreb, Horvatovac 102a. Zagreb, Croatia

After 40 years of active involvement in the teaching of chemistrv this is a good opportunitv to sit back and refiect on

what changes have taken place, on what has been achieved and on what mistakes have been made and to summarize

vvhat could be learnt from the past experience. During the past 40 years several important changes have taken place

in Croatia which have had a huge impact on education in general and hence on the teaching of chemistry as well. In

the 1970-ies a change in the school system was introduced in a typical totalitarian top-down way without any

preliminary investigations, experimental testing or analysis. It proved soon to be a failure, and several generations of

students missed a solid secondary education vvhich they would have had in the older system. The main change

happened in the 1990-ies when Croatia passed from a totalitarian one-party political system into a democratic one.

This was unfortunately accompanied by a five-year war for independence causing huge social and economic

problems in the society in general. The 1990-ies also witnessed the important change in information and

communication technology (ICT): personal computers became largely available, free Internet opened easy access to

many information sources, the production of teaching and learning materials became easier. Ali this brought many

advantages and new opportunities but also some important disadvantages for the quality of teaching. I shall try to

focus on some consequences these developments had on the teaching of chemistry in Croatia not so much in order to

criticize the past or present but rather to warn from future mistakes we should be trying to avoid.

The factors influencing the quality of chemistry teaching in schools can be generally grouped into five categories

l. Teacher competence

48

Nothing can be found in the educational process to replace a good teacher, but another good teacher. A teacher is by

far the most important factor affecting the quality of teaching and leaming. Consequently if vve want to improve the

quality of education, every effort should be made to ensure that teachers should be as competent as possible. This can

be most easily accomplished by increasing their salaries and social status. In Croatia we have been doing the

opposite for more than five decades. Those who enrol chemical studies at the University can choose after 3 years to

opt for 2 more years in the research direction or 2 more years to become chemistry teachers. It has taken us 4 years to

find a single student interested in the teaching profession. Furthermore many teachers of chemistry have not studied

chemistry but nutritional science or chemical technology and accepted a teaching job vvithout adequate training.

2. Teaching and learning materials

Textbooks are still the main material resource for students in order to gain knowledge of a subject. Earlier we had

one publisher who printed ali the school texts. Now that the process has become easier many believe that there is

hardly any knowledge necessary to publish a book and the number of publishers has increased tremendously and far

beyond the capacity of producing textbooks satisfying a minimum standard in quality. Examples will be shown of

almost incredible misinterpretations in chemistry textbooks which have formally met the requirements for

acceptability by scientific and pedagogical experts as well as by a practicing teacher. Furthermore such books have

been recommended to school children by teachers and positively evaluated by the boards of parents. The examples

obviously prove that the whole system is only a farce poorly pretending that evervthing is done objectively, correctly

and fair in the best interesi of the young generations just as we are almost continuously witnessing among the

headlines on economy and politics in the country.

3. Organization

The main centres of knowledge and expertise in a country are located within universities. This applies to Croatia as

well, yet the top-down legislation and administration has hardly changed from totalitarian times and the respective

Ministry establishes agencies vvithout using the experience and expertise available in the Universities. It goes even

beyond by dictating the autonomous universities how to enrol students.

4. Curriculum

It is only very recently that vve have focused some attention to curricula in our educational system. The present

National curriculum has been proposed by teams including experts from the universities chosen by the Ministry and

then adapting the proposal by people from the Ministry's agency. It is not surprising that such methods are met vvith

scepticism in the scientific community and by disappointment of the involved experts.

5. Tradition, culture etc.

This is something we have to live vvith, vve have to take into account, but vve can hardly change even if vve vvanted to.

It is also the reason why vve cannot apply some foreign educational system directly to our conditions.

Proposals

In order to improve the quality of teaching it is essential to improve the status of good teachers. This requires an

evaluation of teacher's vvork in a similar way as it is done for university lecturers. Courses for teachers should be

organized regularly. Textbooks and other educational material should be strictly evaluated by independent experts

49

(not by those chosen by the author and publisher as it is at present). This should preferably be done on the basis of

the text itself and not by the included aitvvork. Authors should be well paid for their work, but only once and not

according to free market rules since parents do not buy the books by their free choice. A new author should always

be required to give a statement of why the new textbook is desirable and this should be evaluated by independent

experts together with the text itself. A collaboration of the Ministry and its agencies with representatives chosen by

the universities should yield better teams for development of strategic plans and educational policies.

Chemical Equilibrium via Dissolution of Solids

Vladimir Stilinović

Faculty of Science, University of Zagreb, Croatia, vstilinovic@,chem.pmf.hr

Chemical equilibrium is one of the most important subjects encountered in high-school chemistry curricula.

Conceptual understanding of dynamic equilibrium is essential for the understanding of numerous chemical

phenomena.1 Unfortunately, this conceptual understanding is often found to be absent, not only among high-school

students, but also among university chemistry students, even among students of senior years.2 One of the reasons

why chemical equilibrium causes so many problems to chemistry students is the way it is introduced. There are two

main problematic points. On one hand the main idea - that a reaction vvill proceed until equilibrium is reached is

contrary to the notion that reactions proceed until ali of the reactant(s) is spent, the notion which is tacitly employed

throughout the teaching of chemistry (in particular in stoichiometric problems). On the other hand, equilibrium is

often introduced through new reactions which were not previously introduced to the students. Worse still, many of

these reactions are inappropriate for experimental demonstration (e. g. thermal decomposition of PC15 or HI). This

leads to students' understanding of chemical equi l ibr ium as an unusual phenomenon which is encountered in some

exotic reactions, rather than a fundamental principle in the vast majority of chemical processes.

A possible solution to this problem is introducing chemical equilibrium by examples which are familiar to

students and also simple to demonstrate experimentally. One type of equilibrium process students are certainly

familiar with is the dissolution of solids.3 The idea that a solid cannot be dissolved in a given amount of solvent at

vvill, but that at a certain point the solution becomes saturated, is the only generally understood example of a process

which does not continue until the "reactants" are entirely used up, and as such presents a natural path for

experimental introduction of chemical equilibrium. This is achieved by studying solutions and their properties in

order to demonstrate the behaviour characteristic of chemical equilibrium.

The most obvious property of a system that has reached equilibrium is that there is no visible change in

macroscopic properties of the system over time. Saturated solution is in equilibrium with the undissolved precipitate

since the amount of precipitate does not change over time (if the solvent does not evaporate). On the other hand, a

system comprising of unsaturated or supersaturated solution and solid precipitate is not in equilibrium since the

amount of precipitate changes (decreases in the first čaše, increases in the second). When the amount of precipitate

stops changing, the system has reached equilibrium - the solution became saturated.

50

A number of experiments can be devised which utilise the behaviour of solutions to demonstrate the basics of

chemical equilibrium. Many of these include measurement of solubility, \vhich is easily feasible by weighing the

residue after evaporation of a sample of solution of known volume. For example, it can be demonstrated that the

equilibrium concentration for a given substance is unique at any given temperature.

c(Ni*) / mol dm-'

b)

-f K I K ,

.... c(Na-)/e0(Na-)

«ci-) / mol dm-3 c(Ha) / mol dnr'

Figure 1. a) Dependence of the concentration of Na+ ions on the concentration of Cl ions in saturated solutions

of NaCl in vvater and four hydrochloric acid solutions of different concentrations. b) the relative change of c^a4),

c(Cr) and K = c^a^CP). c./Na*), c0(Cl~) and K0 denote the values measured in pure vvater.

Adding a substance containing one same ion as the monitored solute will reduce its solubility (common ion

effect). Measurement of solubility of NaCl in a number of HC1 solutions of varying concentrations not only

demonstrates this point, but also allovvs an additional observation - if for each čaše the concentrations of sodium and

chloride ions are calculated, it can be shown that the increase in c(Cl~) is coupled with a the decrease of c(Na*), so

that the value of c^COc^a*) is the same in each čaše. In other words, c^Cr^CNa*) = K, vvhere K is a constant (Fig

1). Thus the concept of equilibrium constant is reached - rather than postulating its existence as is usually done,

students may discover it by themselves, analysing the data gathered from simple measurements done in the

classroom. The definition of equilibrium constant can further be generalised, either by theoretical considerations or

by additional experiments.

Another piece of information which can be attained by solubility measurements is that on the thermal

dependence of equilibrium. Having established the connection between the solubility and the equilibrium constant, it

is easy to demonstrate that if solubility of a substance changes vvith temperature, the equilibrium constant (ant thus

obviously equilibrium itself) also changes. This can easily be demonstrated by measuring the solubility of an

appropriate salt (such as KNO3) at two or more different temperatures.

1. G. M. Bodner, Chem. Educ. Res. Pract., 8 (2007), 93-100.

2. M. A. Pedrosa and M. H. Dias, Chem. Educ. Res. Pract. Eur., l (2000) 227-236.

3. K. L. Cacciatore, J. Amado and J. J. Evans, J. Chem. Ed., 85 (2008) 251-253.

51

Experiment as a mcan to overcome misconceptions on the example of "sublimation" of

iodine

Marina Stojanovska1, Vladimir Petruševski1, Bojan Šoptrajanov2

1 Ss Cyril & Methodius University, Skopje, Republic of Macedonia2 Macedonian Academy of Sciences and Arts, Skopje, Republic of Macedonia

marinam(5),iunona.pmf.ukim.edu.mk

Misconceptions can be extremely persistent and hard to change, creating obstacles to correct further

leaming. Preconceptions, resulting from previous learning experience, play a significant role (both positive and

negative) in the understanding and the quality of the concepts learned by the students. Many students (and,

unfortunately, some teachers) believe that their concepts are correct because the proposed explanations,

corresponding to their understanding of certain phenomena, make sense. Consequently, if students face new

information that, unlike their alternative conceptions, does not fit their explanations, they may ignore it or reject it

because it seems wrong to them. Thus, it is of great importance to identify, confront and correct different

misconceptions students are having.

The most effective chemistry tool is an experiment or a demonstration. Using them it is possible, more or

less easily, to test the correctness (or falseness) of the explanation of a phenomenon. Demonstrations/experiments are

inextricable component of chemistry teaching, and, if properly preformed (better by students than by their teachers),

lead to the development of an active and creative thinking.

Among the numerous examples of misconceptions, one of the widely spread ones is that about the

sublimation of iodine. In many textbooks'"* and by many teachers it is claimed that iodine is a typical example of

sublimation (meaning the process in which a substance changes from solid to gas, vvithout ever passing through a

liquid state at ali). Such statements are found in almost every textbook in Macedonia and therefore are carried over

the students. The notable exception is the book written by one of the authors of the present communication and his

collaborators5.

In order to test the prevalence of this statement and to improve the formulation of the concept of

sublimation, a poli was preformed on 280 high-school students from the first year. The results of the poli are

presented and further discussed in the present communication. The arguments against the erroneous conception

incorporate the design of a relatively simple experiment.

52

~ l altn

I13.6°C 184.4TTemperature (nol to scale)

It is well-known that iodine produces fumes (iodine vapor) upon heating. Violet fumes can be noticed even

at room temperature due to the high vapor pressure of the substance in question. Hovvever, it is possible to obtain

liquid iodine at atmospheric pressure using appropriate apparatus and controlling the temperature just above the

melting point of iodine (114 °C). Additional evidence in support of existence of liquid iodine at atmospheric pressure

is obtained by the phase diagram (see above) of this substance6 from which it can be clearlv seen that iodine first

melts and then vaporizes and that if the heating is carried out in a way as to avoid abrupt rise of the temperature, the

sublimation does not take place.

As a tool for fighting the discussed misconception, a laboratory demonstration, based on a demonstration

proposed earlier5, was devised in which appropriate apparatus and careful control of the temperature just above the

melting point of iodine is emploved.

The authors hope that they will be able to ameliorate the situation in Macedonia and that the present

communication may play a positive role even in regions outside Macedonia.

References:

1. M. Silberberg, Chemistry: The Molecular nature ofmatter and change (4th ed.), McGraw-Hill, New York, 2006.

2. G. Odian, I. Blei, General, organic and biological chemistij (3rd ed.), McGraw-Hill Professional, New York, 1994.

3. E. Wiberg, Anorganska kemija, Zagreb, Školska knjiga,1967.

4. Classic chemistij experiments, Cambridge, Royal Society of Chemistry.

5. M. Najdoski, V. Petruševski, Experiment in chemistij teaching II, Magor, Skopje, 2002. (in Macedonian).

6. R. Petrucci, W. Hanvood, G. Herring, Liquids, Solids, and Intermolecular Forces. General chemistij: Principles and

modern application (8* ed.), Prentice-Hall, Inc., Nevv Jersey, 2002. Retrieved October 19, 2010, from

http://cwx.prenhall.com/petrucci/medialib/media portfolio/text imaees/FG13 18.JPG.

Chemistry teachers' perceptions about their on n evaluation competencies

53

An overvievv of some of the difficulties generated by students from the AP Chemistry exams over the previous five

years will be presented. Suggestions for teachers will be presented.

Students' understanding in chemistry - How to teach

Mei-Hung Chiu

National Taiwan Normal University, Taiwan, mhchiu(g),ntnu.edu.tw

In this presentation, I will introduce and discuss three issues in chemistry learning. The first are types and changes of

students' conceptions in chemistry. The use of two-tier test items for diagnosing students' learning in chemistry and

the teachers' predictions of students' performance were developed and investigated. Second, a survey study on

students' conceptions about models will be introduced and then the results will be compared with previous studies.

Finally, two studies on classroom teaching strategies, such as analogies and model-based approaches, for promoting

students' modeling ability as well as for constructing meaningful internal representations of chemical concepts are

introduced. The effectiveness of the teaching approaches was salient and significant.

For the past few decades, there are large amount of the studies revealed that the students' misconception or

alternative conceptions influenced their understanding of science. Even after university-level instruction, students

still tend to hold alternative conceptions about science. In order to understand what and how students learn in the

school, different formats of assessment were developed to diagnose learning outcomes. The outcome of the

assessment determines how teachers interpret students' achievement in learning sciences. In this presentation, the

design and outcome of two-tier test items will be introduced.

Chemists use models to explain the properties and theories of matters and phenomenon, such as atomic theory and

ideal gas law. Learning chemistry cannot ignore the important role of models that construct a connected structure of

knovvledge about chemistry. Development of students' conceptions of models and modeling ability has been

increasingly gaining attention from science researchers and educators in science education over the past two decades.

Hovvever, since an instrument for investigating students' and experts' conceptions of models was developed by

Grosslight, Jay, and Smith (1991) almost 20 years ago, most of the studies in the area of models have tended to adopt

interview techniques to collect students' conceptions of models. In order to collect more data about students'

conceptions of model, a need for developing a questionnaire is considered. Therefore, we (Chiu, et al., submitted)

developed a set of questionnaire to investigate what students' conceptions are about nature of models.

Halloun (1996) proposed five stages to have students use scientific models in solving a range of paradigmatic

problems in physics. These five stages are selection, construction, validation, analysis, and deployment. These

components allow the students to construct the composition and the structure of the model they selected, to evaluate

the internal consistency of a model, to process the mathematical model and try to get ansvvers, and then to interpret

Renata Ruić

Gimnazija Franje Petrića, Zadar, Hrvatska, renata.ruic(g).zd.t-com.hr

This paper presents the results of empirical studies evaluating the teacher of chemistrv and biologv and chemistry in

primary and secondary schools. The survey is based on the vievvs of 141 teachers from ali over the Croatian collected

by specially designed questionnaire consisting of open and closed questions and Likert scale. The survey included

teachers vvho had finished teaching, but also nonteaching studies, which were later taken psychological-pedagogical

group of subjects. The aim of this study was to determine teachers' opinions about their own competencies to

monitor and evaluate student achievement. Examinees feel a lack of skills in the field of assessment of student

achievement. Teachers haven't attained necessary competencies to evaluate the students by an undergraduate degree,

but they have developed skills through practice and through sharing experiences with close colleagues. The results of

this study show no statistically significant differences in assessing their own competencies and the manner of

acquisition of competences between the teachers who has finished teaching education of those vvho gained their

teaching competence through additional pedagogical and psychological education.

Logarithms in aqueous solutions

Franka Miriam Brueckler

Department of Mathematics, Faculty of Science, University of Zagreb, Croatia, bruckler(5).math.hr

Mathematics is often viewed and taught as a subject almost completely unconnected to chemistry, particularly in the

pre-university levels of education. Surely, there are some exceptions: the arithmetic techniques necessary for

stoichiometry calculations and the use of graphs and mathematical functions. The last of the mentioned exceptions is

a particularly problematic one, both from a mathematical and a chemical viewpoint. From the mathematical point,

the functions used are often not understood vvell enough, sometimes even wrongly used, and usually they are reduced

to buttons on a calculator1, both by chemistry teachers and pupils. From the chemical vievvpoint, the mathematical

functions are often an obstacle because due to the mathematical formalism, becoming an opaque veil shading the real

content they represent. As chemistry teachers often have very little mathematical training (and viče versa), it is hard

to better integrale the teaching about mathematical functions and their application.

One of the particularly important class of mathematical functions for ali levels of teaching chemistry are the

logarithmic functions. The pupils first meet logarithms in chemistry courses when learning about the pH, and this is a

topic studied on ali levels of chemistry education. It has been often noticed2 that most of the main problems for

pupils when learning about acids and bases are mathematical, because pupils usually do not knovv enough

mathematics. Unfortunately, chemistry teachers often lack the sufficient knowledge about exponential functions and

logarithms and are unable to explain them effectively to their pupils, thus being unable to help the pupils. There have

54

been several studies on how students learn exponential and logarithmic functions, e.g. by Weber3, and some (e. g.

Strom4) on how science teacher think, reason and learn about them during their in-service training. Less practical

help and instruction materials was offered to chemistry teachers to give them ideas how to reduce the problems they

encounter when teaching about topics including logarithms.

The aim of this contribution is to present an, as far the author knows nevv, approach to teaching logarithms for

chemistry, adapted particularly for the use in the chemical classroom, at the same time being mathematically sound

and not contradictory to the usual presentation of logarithms in the mathematics classroom. The idea is to develop

the notion of logarithm starting from the chemical viewpoint, founded on experiments with measuring the pH of

aqueous solutions, and to conclude about the basic properties of logarithms from the observed facts. Although it was

not yet systematically tested, the teachers' responses in informal interviews were very favourable. Also, by

participant observation during and after the presentation of the proposed method at a recent meeting of the

Educational Section of the Croatian Chemical Society it was possible to conclude that this suggestion could be

effectively used in the classroom.

Additionally, we plan to address the possible, unfortunately frequent, mistakes and misconceptions that ariše from

incorrect usage of mathematical formulas as a subject in their own right, without taking into account under what

assumptions or approximations they were introduced. This kind of problems was discussed e.g. by Matsuomot et af,

and we shall address in more detail the problems connected to the interpretation of formulas containing logarithms

and graphs that use a logarithmic scale (calculations of pH, titration curves etc.).

In effect, we hope to show that there are simple ways to improve the understanding and correct usage of logarithms,

and thus induce positive changes in the mathematical part of the chemistry teacher in-service training by introducing

an "untraditional" method of developing mathematical notions from an applied context.

References

1. D. J. Watters and J. J. Watters, Biochem. Mol. Biol. Educ. 34 (2006) 278-284

2. M. Drechsler and H.-J. Schmidt, Chem. Educ. Res. Pract. 6 (2005) 19-35

3. K. Weber, in Proceedings of the 24th Annual Meeting of the North American Chapter of Mathematics

Education (2002), pp. 1019-1027. Retrieved October 14,2010 from http://eric.ed.gov/PDFS/ED471763.pdf

4. A. D. Strom, in Proceedings of the 28lh Annual Meeting of the North American Chapter of the International

Group for the Psychology of Mathematics Education (2006), pp. 624-630. Retrieved October 14,2010 from

http://www.pmena.org/2006/cd/book.pdf

5. P. S. Matsumoto, G. Tong, S. Lee and B. Kam, J. Chem. Edu. 86 (2009) 823-826

Chemical Equilibrium Misconceptions in Croatian Secondarv Schools

Draginja Mrvoš-Sermek, Ivan Vicković, and Andreja Kuštelega

Chemistry Department, Faculty of Science, University of Zagreb, Croatia, vickovic@chem.pmf.hr

55

Often misconceptions in understanding of dinamic nature of chemical equilibrium have been found. Some

problems concerning the chemical equilibrium have been set in the State graduation exam for secondarv

schools officiallv carried out for the first time in the 2009/2010 academic year as well as in the

experimental State graduation exams of 2007 to 2009. This research was inspired by inadequate results

of mentioned experimental exams.

Chemical equilibrium is one of the basic concepts in both secondary schools and univers'rty

chemistry curriculum and it was a subject of many educational studies<1'2) ali over the world. Our research

covered the sample of 220 freshmen of the Faculty of Science having six year chemistry education. The

samle was observed through 2007 to 2009 period. The aim of the research was to find out: (i) the level of

understanding of the chemical equilibrium, (ii) the most frequent alternative concepts of understanding the

chemical equilibrium, (iii) the level of durability of knowledge acquired in secondary school, as well as its

applicability in the university subject of General Chemistry, and (iv) the appropriateness of questions

asked in the experimental State graduation exams of 2007 to 2009. Our test comprised of three open-

ended questions. Two of these questions have already been asked in experimental State graduation

exams of 2007 to 2009, and the third one was based on the model of "Conceptual Ouestions" on Le

Chatelier's Principle(3).

The issue of understanding the concept of chemical equilibrium has not been investigated in Croatia untill

now, neither over students or teachers population. The observed grups of freshmen exhibited the most of the

misconceptions already described in chemical education literature. Similarly as it had been shown by the other

authors(4), we found that misunderstanding is present on the conceptual as well as on the symbolic level. In order to

understand the background of the situation, we plan to submit the teachers comunity to the similar investigation.

It is planned to make good use of the fmdings on the misconceptions about chemical equilibrium (i) in life-

long learning education for in-service teachers, (ii) in lectures of Methods of teaching chemistry as a subject in pre-

service teacher study programme, (iii) in development of didactic methods to help students understand dvnamic

chemical equilibrium using animations on interactive whiteboard.

(1) Banerjee, A.C. (1991, October). International Journal of Science Education, (Vol 13, Issue 4), 487 - 494

(2) D. Cheung, D. (2009). Using think-aloud protocols to investigate secondary school chemistry teachers'

misconceptions about chemical equilibrium, Chem. Educ. Res. Pract., 10, 97-108.

(3) Benjamin P., & Huddle, (1998)., J. Chem. Educ., 75,1175-1175.

(4) Raviolo, A., & Garritz, A (2009). Analogies in the teaching of chemical equilibrium: a synthesis/analysis of the

literature, Chem. Educ. Res. Pract., 10, 5-13.

56

Rezultati istraživanja o integriranju konceptualnih znanja iz kemije i fizike studenata prve

godine studija kemije Prirodno-matematičkog fakulteta Sarajevo

Ines Vidović, Meliha Zejnilagić-Hajrić, Zalkida Hadžibegović, Semira Galijašević

Prirodno-matematički fakultet, Univerzitet u Sarajevu, Bosna i Hercegovina

ines vidovic@vahoo.com. mzejnilagic@yahoo.com. zalkidah@vahoo.com. semira.galiiasevic@gmail.com

Proces stjecanja znanja sastoji se u integriranju novostečenih znanja sa znanjima koje svaki pojedinac već posjeduje.

Učenici i studenti ne bi trebali učiti samo pojedinačne koncepte iz prirodnih znanosti, nego treba da te koncepte

međusobno integriraju1. Upotrebljiva znanja, a posebno iz kemije i fizike, zahtijevaju direktnu međusobnu

povezanost, koja je neophodna za sveobuhvatno razumijevanje prirode, kao i za primjenu znanja u svrhu rješavanja

problema. Kako i u kojoj mjeri studenti prve godine studija kemije, na Prirodno-matematičkom fakultetu,

Univerziteta u Sarajevu, integriraju prethodna i nova znanja iz fizike u kemiji i obratno, bio je jedan od ciljeva

istraživanja, provedenog na Odsjeku za kemiju, tijekom zimskog semestra, akademske 2009./2010. godine2'3. U

ovom radu predstavljeni su neki rezultati spomenutog istraživanja, kao i vizija budućih istraživanja.

Osnovni cilj istraživanja o univerzitetskoj nastavi kemije i fizike bio je dobijanje podataka o kvalitativnoj i

kvantitativnoj mjeri integriranih konceptualnih znanja iz fizike i kemije, na uzajamnoj osnovi, radi sagledavanja

uzroka nedovoljne prolaznosti studenata prve godine studija kemije, naročito iz fi/ike, sa svrhom da se pronađu

načini za poboljšanje uspjeha studenata, ali i mjere i aktivnosti koje bi se mogle poduzimati. Istraživanje provodi

novoosnovana grupa za istraživanje, sastavljena od kemičara i fizičara uključenih u nastavu iz predmeta opće kemije,

opće fizike i metodike nastave kemije. Metode istraživanja su raznovrsne, kao što je metoda anketiranja, testiranja,

intervjuiranja i komparativna metoda, dok su instrumenti istraživanja tipa upitnika za dobijanje općih podataka o

studentima, ulazni test, završni test i prilagođeni sadržaji za intervjue. Dobijeni su prvi rezultati u ovom istraživanju,

a na osnovu testiranja studenata, koje je provedeno na početku semestra, odnosno njihovog studija kemije, kroz

ulazni test o znanjima iz prethodnog školovanja, prvenstveno srednjoškolskog, i ponovljenog testa na kraju prvog

semestra, a nakon realizacije nastave iz predmeta Opća kemija I i Fizika I. Testovi su sadržavali 30 pitanja, od kojih

su 15 pitanja iz kemije, a 15 pitanja iz fizike. Ulaznom testiranju pristupilo je 74, a ponovljenom testu 54 studenta

kemije. Iz brojnih općih podataka o studentima, dobijenih nakon dva provedena upitnika, značajan je za istaknuti

podatak da je struktura studenata bila očekivana i da su najbrojniji studenti oni koji su završili gimnazijsko

obrazovanje, sa najvišim ocjenama. Međutim, prema rezultatima ulaznog testa, njihovo predznanje ne odražava ovu

činjenicu. U prilog ovakvoj ocjeni je i grafički prikaz rezultata ulaznog i ponovljenog testa, koji prema priloženom

histogramu (Slika 1.), koji govori o lošim rezultatima ne samo na ulaznom, nego i na ponovljenom testu, pri čemu je

očigledno da je mali broj studenata, u oba slučaja, prešao prag prolaznosti na testu, koji je iznosio samo 55% od

mogućih bodova.

57

Slika 1. Usporedba broja postignutih bodova studenata kemije na Testu l (TI) i Testa 2 (T2)

* Kriterij prema pragu prolaznosti na Univerzitetu u Sarajevu.

Jedan od zaključaka, značajan za samo istraživanje, odnosi se na preferencije studenata kada je u pitanju izbor

studija. Studenti, njih 40%, koji su izabrali studij kemije kao svoj prvi izbor, i sami su došli na studij sa predznanjem

koje im stvara poteškoće u integriranju novih i prethodnih znanja. Ovo je potkrijepljeno rezultatima da je na

ponovljenom testu svega 14 (26%) studenata postiglo prag prolaznosti na testu. Ovo govori o nužnosti poduzimanja

sinkroniziranih aktivnosti sa razine univerziteta i odgovarajućih službi u nadležnim ministarstvima, ali i samim

srednjim školama. Potaknuta i drugim relevantnim pokazateljima o postojanju poteškoća za ispitivanu grupu

studenata, istraživačka grupa je organizirala seminar i radionice za nastavnike osnovnih i srednjih škola u Federaciji

Bosne i Hercegovine, na temu aktivnog učenja, što se pokazalo kao korisno i kolaborativno.

Kao vizija o budućem radu ove istraživačke grupe, a na temelju uočenih problema s kojim su suočeni studenti i

nastavnici involvirani u nastavu kemije i fizike, je ostvarenje jednog kolaborativnog odnosa koji će se realizirati kroz

nužnu edukaciju putem seminara, radionica, tematskih razgovora, ali i drugih aktivnosti s namjerom da se dobiju

konačni odgovori da li je ovo samo trenutno stanje ili se naziru tragovi pojave da su budući studenti kemije

nedovoljno ili neadekvatno pripremljeni za studij kemije, i l i je pak postojeći program studija kemije neprilagođen

mogućnostima studenta, među kojima je i oko od 20% onih koji se opredjeljuju za nastavnički poziv.

Literatura

1. K.S. Taber, Int.J.Sci.Educ. 30 (2008) 1915-1943.

2. M. Zejnilagić-Hajrić, Z. Hadžibegović, S. Galijašević, I. Vidović, Metodološki postupci i rezultati

longitudinalnog istraživanja realizacije programa predmeta opće fizike i kemije na prvoj godini studija

kemije na Univerzitetu u Sarajevu, IV savjetovanje o reformi visokog obrazovanja na Univerzitetu u

Sarajevu, Sarajevo, 2010.

58

3. M. Zejnilagić-Hajrić, Z. Hadžibegović, S. Galijašević, I. Vidović, Značaj integriranih znanja iz hernije i

fizike studenata na Prirodno-matematičkom fakultetu u svjetlu Bolonjskog modela studija, III Međunarodni

naučno-stručni skup „Edukacija nastavnika za budućnost", Zenica, 2010.

Usabilitv of tnedia in chemistrv education

Anton Depope

Faculty of Science, University of Split, Croatia, antdcp@pmfst.hr. depoue.anton(g)gmail.com

When creating the chemistry curriculum we must, first and foremost, have a clear idea about the

goals of the educational process for the students observed. It's tempting to believe that for

students who are preparing for \vorkplace rooted in the practical use of chemistry (future

chemical technicians but also the pharmaceutical technicians and laboratory technicians) teaching

of chemistry needs to be firmly based on experimental methods, vvhile for youth inclined tovvards

theory the education process should be based almost exclusively on theoretical basis. Such belief

is very superficial and can easily mislead us. Even if the success of the educational process is

measured exclusively by the results that students achieve on standardized tests, it is important to

deeply reflect on the usefulness of the educational model we have chosen (classical teaching,

\vorking in small groups, students1 projects, etc.) as well as the (qualitative and quantitative)

rationale for the application of instructional media and chemical experiments in teaching. In my

presentation I'll stress the importance of proper balance betvveen practical projects and classical

teaching due to different mechanisms of learningl. I'll also provide short examples to

demonstrate when it's best to use the classical teaching, when student collaboration in small

groups, and when students should work independently. I base my ideas of student motivation,

attention and \villingness to participate on the classical anatomical-neurological model of

lateralization of brain fiinction as well as the Maslow's theory of motivation2 and its

reverberation in Glasser's theory of the quality school.3'4

McLuhan's media theory5,6 will allow me to explain how the usage of any teaching aid has far-

reaching effects on the students, to consider situations in which these effects are beneficial (for

example, when talking about events on the molecular level, plainness of visual media is of great

59

help in explaining the important chemical concepts) as well as situations in which they are

counter-productive and in which the real tangible chemical experiment as a personal experience

for the student is a priceless teaching tool. Following McLuhan's paradigm of multilinear

educational process I wil l demonstrate that in said context7 (and in correlation with

beforementioned experiences from educational psychology) even most rigid cybernetic models of

teachingS require the application of diverse teaching methods and tools as well as the emotional

involvement of students (as opposed to the passivity of students found in scholastic paradigm).

Using the lecture on electrolysis as an example, I will explain to the audience how the complex

concepts of hyperreality, hot and cold media, multimodality, and immersion manifest in their

everyday work with students. In this process, I will explain the application of pure text, illustrated

text (as found in textbooks), the text as a transcript of verbal communication (lecture notes),

educational video9, as well as the most advanced government's system for distance learninglO.

Examples with aids and content with which they are already very familiar should enable the

members of the audience to apply informations from my theoretical work in their classroom, and

also to deeply grasp how and why it's best use the media in the teaching of chemistry as part of

the overall educational process.

References:

1) T. Grgin, Edukacijskapsihologija, Naklada Slap, Jastrebarsko, 1997.

2) A.H. Maslovv, Psychological Reviev, 50 (1943) 370-396.

3) W. Glasser, Control Theory, HarperColIins, Scranton, 1985.

4) W. Glasser, The Quality School: Managing Students Without Coercion, Harper & Row, New Vork, 1990.

5) M. McLuhan, Understanding Media: The Extensions ofMan, McGraw Hill, New Vork, 1964.

6) M. McLuhan, The Gutenberg Galaxy, University of Toronto Press, Toronto, 1967.

7) N. Rot, Znakovi i značenja, Nolit, Beograd, 1982.

8) R. Stammers & J. Patrick, The Psychology ofTraining, Methuen, London, 1975.

9) FWU Germany, Elektroliza, Zagreb Film, Zagreb, 1993. (educational DVD)

10) National portal for distance-learning "Nikola Tesla", http://lms.carnet.hr/ (accessed November 3rd, 2010.)

Visualisation as an aid to teach the structure-function

realtionship of biological macromolecules

60

Marina Luetić

3. gimnazija, Matice hrvatske 11, HR-21000 Split, Croatia

Most of recent research in the field of education strongly recommends visualization in daily teacher's practice,

especiallv vvhen it comes to teaching science. Science is demanding not only to teach, but also to learn, and vvithout

proper visualization it can become very difficult for everyone involved. Hovvever, we could not find a research that

would investigate the impact of visualization on student's accomplishments in secondary education in Croatia.

Therefore we decided to investigate the impact and the relationship betvveen 2D and 3D visualization on the learning

outcomes in chemistry teaching. We were also intrigued by somevvhat contradictory reports regarding gender-related

differences in 2D vs. 3D perception abilities. It seams that among researchers there is no agreement regarding this

factor. In Croatia, at the secondary education level, we could not find any published reports on this subject.

Therefore, we designed and conducted research study the results of which referred not only to the impact of different

kinds of visualization in teaching chemistry, but also to genderrelated differences. The research study was conducted

on a sample of 149 fourth grade grammar school students. We divided them into three groups: control group (vvith no

treatment other than usual teaching process) and two experimental groups that were taught using different kinds of

visualization: E l (using 2D and 3D static visualization tools) and E2 (using 3D dynamic visualization tools, in

addition). According to the results (gained from tests vvith objective type

of questions and from questionnaires), we measured students learning outcomes in chemistry, as well as their

satisfaction vvith different ways of teaching. In order to describe this data, we performed statistica! measures and

analyses: mean (as centra! tendency measure) and standard deviation (as measure of variability). Furthermore, in

order to validate our hypotheses, we used one-tail and two-tail ANOVA analyses (along with the t-tests for

independent samples). On this basis, we concluded that there was no statistical significance regarding 2D vs. 3D

visualisation tools in chemistry teaching. On the other hand, although there exsisted some gender-related differences

in students' achievements (in favour of females), vve didnt found that they were due to the nature of visualisation (2D

or 3D) used for teaching. Hovvever, students from the experimental E2 group (additional 3 D dynamic visualisation

tools - computer animations) vvere more attracted by and involved in this kind of teaching. Although the results didn't

show statistical significance in favour of 3D visualisation (computer animations, especially), vve must conclude that

this kind of teaching is certainly more efficient way than traditional teacher-oriented lessons. By using this kind of

visualisation tools in everday teaching practice chemistry teachers are given the opportunity to enlighten students

vvith somevvhat complex and abstract chemistry concepts.

Koliko prošla iskustva nastave kemije utječu na percepciju

i oblikovanje kompetencija budućih nastavnika kemije

Marina Luetić1, Roko Vladušić2, Nenad Judaš3

61

1 III. gimnazija, Split, Hrvatska2 Prirodoslovno-matematički fakultet Sveučilišta u Splitu, Hrvatska

3 Prirodoslovno-matematički fakultet Sveučilišta u Zagrebu, Hrvatska

marinaluet(a)gmail.com vladusic(a>.pmfst.hr judas(g).chem. pmf.hr

Tematski strukturiranim anketnim upitnikom prikupljeni su podatci o osnovnim društvenim i

socijalnim značajkama studenata kemije na nastavničkim smjerovima Prirodoslovno-

matematičkih fakulteta, njihovom poimanju svrhe učenja i poučavanja kemije, kompetencijama

dobrog nastavnika i odabiru odgovarajućih strategija u konkretnim, precizno opisanim nastavnim

scenarijima. Kroz iskustvo studenata stečeno u prethodnom školovanju reflektirani su načini

poučavanja osnovnoškolskih i srednjoškolskih nastavnika kemije. Na taj se način uspjelo utvrditi

u kojoj mjeri je iskustvo nastave kemije na prethodnim razinama oblikovalo studente - buduće

nastavnike kemije.

Pokazalo se, unatoč činjenici da nastavnički smjerovi kemije većini studenata nisu prvi izbor,

tijekom studija raste zadovoljstvo odabranim pozivom. Uočeno je da se studentski modeli

poučavanja značajno razlikuju od modela koje su (koje bi) primjenjivali njihovi nastavnici. Nije

utvrđena statistički značajna razlika u načinima poučavanja kemije između nastavnika osnovnih i

srednjih škola.

Visualisation as an aid to teach the structure-function

realtionship of biological mač roni olecu les

Marina Luetić

3. gimnazija, Matice hrvatske 11, HR-21000 Split, Croatia

Most of recent research in the field of education strongly recommends visualization in daily teacher's practice,

especially when it comes to teaching science. Science is demanding not only to teach, but also to learn, and vvithout

proper visualization it can become very difficult for evervone involved. Hovvever, we could not find a research that

would investigate the impact of visualization on student's accomplishments in secondary education in Croatia.

Therefore we decided to investigate the impact and the relationship betvveen 2D and 3D visualization on the learning

outcomes in chemistry teaching. We were also intrigued by somewhat contradictory reports regarding gender-related

differences in 2D vs. 3D perception abilities. It seams that among researchers there is no agreement regarding this

factor. In Croatia, at the secondary education level, we could not find any published reports on this subject.

62

Therefore, vve designed and conducted research study the results of which referred not only to the impact of different

kinds of visualization in teaching chemistry, but also to genderrelated differences. The research study was conducted

on a sample of 149 fourth grade grammar school students. We divided them into three groups: control group (with no

treatment other than usual teaching process) and two experimental groups that were taught using different kinds of

visualization: E l (using 2D and 3D static visualization tools) and E2 (using 3D dynamic visualization tools, in

addition). According to the results (gained from tests with objective type

of questions and from questionnaires), vve measured students learning outcomes in chemistry, as vvell as their

satisfaction with different ways of teaching. In order to describe this data, vve performed statistica! measures and

analyses: mean (as central tendency measure) and standard deviation (as measure of variability). Furthermore, in

order to validate our hypotheses, vve used one-tail and two-tail ANOVA analyses (along with the t-tests for

independent samples). On this basis, vve concluded that there was no statistica! significance regarding 2D vs. 3D

visualisation tools in chemistry teaching. On the other hand, although there exsisted some gender-related differences

in students' achievements (in favour of females), vve didn't found that they were due to the nature of visualisation (2D

or 3D) used for teaching. Hovvever, students from the experimental E2 group (additional 3 D dynamic visualisation

tools - computer animations) vvere more attracted by and involved in this kind of teaching. Although the results didn't

shovv statistica) significance in favour of 3D visualisation (computer animations, especially), vve must conclude that

this kind of teaching is certainly more efficient way than traditional teacher-oriented lessons. By using this kind of

visualisation tools in everday teaching practice chemistry teachers are given the opportunity to enlighten students

with somevvhat complex and abstract chemistry concepts.

Contemporary approach to in-service teacher training

Olgica Martinis

Education & Teacher Training Agency, Hrvatska olgica.martinisfSžazoo.hr

The starting point of this paper is the claim that the approach to in-service training of chemistry teachers in

secondary schools should be in the function of their professional development, what vvill result vvith better student

attainment, improvement in the quality of chemistry teaching in secondary schools, and the personal and professional

satisfaction of chemistry teachers.

The paper deals vvith the importance of implementing contemporary approaches to in-service training of chemistry

teachers in Croatia, and describes the difference betvveen the terms contemporary approach to in-service teacher

training and professional development of teachers vvhich is a vvider term encompassing six characteristics of the

professional development of teachers. This framevvork of the professional development of teachers in general, and

chemistry teachers in particular, outlines the rationale behind the changes underpinning the contemporary approaches

to in-service training of chemistry teachers in accordance vvith different levels in the education system, and

highlights the importance of vvider understanding of professional development as a series of activities undertaken by

63

and justify the ansvvers asked in the problems. Finally, students may use this original model to describe, explain or

predict nevv situations. Chiu (2007) adopted conceptual change theory to the modeling process and suggested to have

a step called model reconstruction to reflect on the process of conceptual change while constructing their mental

models in learning science. Hovvever, perhaps due to a lack of existing Information, frame\vorks, and structures for

guiding teachers in engaging children in model-based inquiry practice, there is an absence of modeling activities in

school science classrooms (Schvvarz & Gvvekvverere, 2007). In science classrooms, it is essential to emphasize the

role and purpose of scientific models and then provide examples of or opportunities to construct model-based

cognitive tools for learning science (Treagust, Chittleborough, & Mamiala, 2002). The follovving sections w i l l draw

some examples to illustrate the issues mentioned above.

A. Students' learning in chemistrv and the teachers' predictions of students' performance

Study 1: Gas particle

A series of studies in gas particles were conducted (Chiu, 2007; Chiu and Chung 2008; Chiu and Wu, 2008). One of

the studies aimed to investigate students' development of their conceptions about gas particles (Chiu and Wu, 2008).

In the study, 492 participating students from the 6th to university were involved. Results revealed that students'

incremental conceptual structures progressed from the 6th grade to the university level. The students started from

considering a continuous model to the particulate nature of gases and random movement of gas particles (namely

scientific model). Their most robust conception about the nature of gas particles was that something exists between

gas particles. Although this finding was not new to secondary school students in this field of research, we found that

even 30% of the university students still held this conception. In addition, another robust conception that can rarely

be repaired was that the siže of individua! gas particle is affected by the temperature and pressure. Finally, the

varieties of mental models remained the same from the 6* graders to the university students; however, the correct

main conceptions of the students' mental models gradually incremented and developed into their knovvledge

structures.

Study 2: Acid/Base

A qualitative study on acid and base was conducted to 38 ninth graders to investigate what the differences of

students' mental models changed before and after instruction. Their teacher's prediction of the students' performance

was compared. The results revealed that the teacher in the study made accurate anticipations of her students' mental

models in the čaše of the high achievers but inaccurate anticipations of the low-achievers' mental models. As a

result, the teacher's instruction reinforced the lovv-achievers' incorrect mental models (Details could be found in Lin

and Chiu, 2010).

B. Students' perception about the models

A questionnaire containing 46 items about models vvas piloted vvith 68 10th graders when the test items vvere first

developed. The \vording of the items vvas modified based upon the students' informal intervievvs in the pilot study.

10

an individual, a teacher, in the process of his/her lifelong learning. The framevvork also identifies the forms of the

professional development and gives special attention to holistic approach to development. Active in-service teacher

training implies better connection between the theory and practice, i. e. the need to design in-service teacher training

on the basis of the problems/needs identified in the practice. In accordance with the above-mentioned, schools as

educational institutions should have their teacher training strategies developed in accordance with the specific needs

of their teaching staff, students, parents and the community. This approach allovvs for a wider scope of activities of

professional development and actions of teachers of chemistry, in accordance with the previouslv identified needs.

Some actual and potential students' misconceptions regarding chemical reactions

in the chemistrv teaching in Republic of Macedonia

Marina Stojanovska1, Bojan Šoptrajanov2 and Vladimir M. Petruševski1

' Ss Cyril & Methodius University, Skopje, Republic of Macedonia2 Macedonian Academy of Sciences and Arts, Skopje, Republic of Macedonia

marinam@iunona.pmf.ukim.edu.mk

Chemistrv has a distinctive vocabulary of vvords which have specific meaning for a chemist1. Difficulties

may ariše among students because of teachers' unavvareness of the problems that students (novices, particularlv)

experience with these terms. Teaching students without grasp of chemistry vocabularv may lead to development of

their own understanding of chemical concepts, vvhich are not always scientifically correct. Problems2 have been

identified in characterizing the properties of matter and chemical change vvhich are caused by misinterpretations of

the relationship between matter and its particles. Very often, the properties of a substance are sometimes considered

as identical to the properties of the particles themselves, vvithout taking into consideration the important differences

betvveen the macroscopic and the particulate level. Students need to be given opportunities and more time to learn the

chemists' meanings rather than to be left to term definitions alone. Time is also important for teachers to discover

students' ideas and to address them.

Chemical reactions are at the heart of the entire chemistry, as they give insight into the type of chemical

changes taking part in the system.

Many misconceptions are identified in the literature3"6, and the available lists are certainly not complete.

Researchers and educators continue to discover new misconceptions and correct them but there are many common

phrases/statements that are used ali too often by teachers and textbook vvriters and are (usually, inadvertently) a

source of new (or slightly different) misconceptions. Some of them are:

1) Balance the chemical reaction betvveen zine and hvdrochloric acid.

2) Which of the follovving reactions are reversible?

64

3) Judge (qualitatively) the activitv of the metals on the basis of the reaction rate with diluted hvdrochloric or

sulfuric acid.

4) With how many vvater molecules crvstallizes copper(II) sulfate in the chemical reaction between the

anhydrous salt and an excess of vvater?

5) C, H and O atoms of alcohol (C2H5OH) will burn out when it is lighted.

6) In a chemical reaction, substances exchange outer electrons to form new substance(s).

7) Chemical reaction will continue until ali reactants are exhausled.

8) The recrystallized substance (after it is at first dissolved) is identical with the starting material.

Ali of the above statements/questions contain a part (bolded) that is a possible source of misconceptions.

These are analyzed and a possible correction (rephrasing) is offered.

To check for the presence of such misconceptions in the minds of students (and teachers), tests were carried

out and their results vvere analyzed.

References:

1. http://www.springer.co m/cda/content/document/cda_downloaddocument/9783540709886-

cl.pdf?SGWID=0-0-45-646108-pl73832306 (Retrieved October 19, 2010).

2. I. Eilks, J. Moellering, N. Valandies, EuroasiaJ. Math. Sci. & Tech. Ed. 3(4) (2007) 271-286.

3. C. Horton (with other members of the Modeling Instruction in High School Chemistry Action Research

Teams at Arizona State University), Student Alternative Conceptions in Chemistry, Worcester, MA, 2004,

pp. 31-70.

4. V. Kind, Beyond appearances: Students' misconceptions about basic chemical ideas, 2nd ed., Durham

University, Durham, 2004. http://www.rsc.org/images/Misconceptions update_tcml8-188603.pdf

(Retrieved October 19, 2010)

5. K. D. Tan, D. F. Treagust, Aust. J. Ed. Chem. 60 (2002) 13-18.

6. Č. Geban, G. Bayir, Hacettepe Universitesi E|itim Fakultesi Dergisi 19 (2000) 79-84.

Analiza pisanih zadaća iz kemije: pogrešno shvaćanje stehiometrijskih odnosa i drugiproblemi u rješavanju

Marina Luetić3. gimnazija, Matice hrvatske 11, 21000 Split

U današnje se vrijeme čuju i poneki protesti protiv sve većeg broja ispita u pisanom obliku i iz svih

nastavnih predmeta. Prigovori tomu su brojni, neki i opravdani (narušavanje kontakta učenik-nastavnik, brzina

pisanja, disleksija ili disgrafija i si.). Unatoč tomu, pisane zadaće imaju svoje mjesto u procesu vrjednovanja

učenikovih postignuća. One nastavniku prirodnih predmeta (kemija, fizika) mogu biti vrijedan izvor informacija o

učenikovu napretku, a mogu otkriti i razloge njihova nenapredovanja. Da je tomu tako, pokazuje i ova analiza,

65

provedena na zadaćama učenika 2. razreda gimnazije i to u okviru nastavnog sadržaja vezanog uz jednadžbu stanja

idealnog plina i stehiometriju jednadžbi kemijskih reakcija. Analiza je provedena na pisanim zadaćama 88 učenika u

okviru uobičajenog pisanog provjeravanja njihova znanja i klasičnim testom s ukupno pet brojčanih zadataka.

Rezultati nedvojbeno pokazuju da su smanjena učenička postignuća nastala zbog nerazumijevanja simboličkog

jezika. Postoji naznaka i drugog problema - pogrešnog razumijevanja stehiometrijskog odnosa množina, što nas vodi

k dubljem uzroku (nerazumijevanje odnosa množine i mase). Time je potvrđena direktna veza između kognitivne

strukture učenika (struktura dugoročnog pamćenja) i problema u rješavanju (brojčanih) zadataka. (1)i(2)i<3) Analiza

zadaća pokazala je i da su učenička smanjena postignuća u dobroj mjeri povezana s nedovoljno razvijenim

vještinama matematičke obrade informacija. Ono što je osobito zabrinjavajuće jest činjenica da se radi o

nesnalaženju u osnovnim matematičkim operacijama koje se izvode na matematičkim zapisima određenih zakonitosti

(opća plinska jednadžba, izraz za množinu, brojnost, račun koji uključuje dimenzije fizičkih veličina i si.). Je li i

ovdje u pitanju nemogućnost povezivanja simboličkog jezika i kemijskih koncepata ili se radi nemogućnosti učenika

za svrhovitom integracijom dvaju simboličkih jezika? Ova analiza ne može dati odgovor na ovo pitanje pa bi neko

buduće istraživanje u tom pogledu moglo pomoći razvoju nastavničke prakse iz obaju nastavnih predmeta.

(1) Kempa, R.F. (1991). Students' learning difficulties in science. Causes and possible remedies. Ensenanza de lasCiencias, 9, 119-128.

(2) Kempa, R.F., & Nicholls, C. (1983). Problem-solving ability and cognitive structure - an exploratoryinvestigation. European Journal of Science Education, 5, 171-184.

(3) BouJaoude S. and Barakat H., (2000). Secondary school students' difficulties with stoichiometry, school ScienceReview, 81, No. 296, 91-98.

What Physics Teachers Think about their Education

'Tanja Ćulibrk, 2Ivica Luketin, 3Damir Rister, 2Franjo Sokolić

'OŠ Brezovica, Zagreb, Hrvatska2Odjel za fiziku, Prirodoslovno-matematički akultet u Splitu, Htvatska

3Institut za društvena istraživanja, Zagreb, Hrvatska

risterfajidi.hr tania.culibrk(S>skole.hr Ivica.Luketin@pmfst.hr Franjo.Sokolic@pmfst.hr

We present the results of the questionnaire with 120 (10% sample) phvsics teachers in elementary and high school

conceming their universitv education and the different forms of permanent education, to which they participated

after starting teaching. Average teachers grade for contents of university study is 3.3, and for pedagodic methods

66

during study grade is 2.9, in scale 1-5. They are critical to the university education because it is very formal,

insisting more on mathematical than on the conceptual aspects. Also, there is no enough formation for work with

children with difficultis. Teachers suggests modification in university education and the different forms of

permanent education : more practice in clsssrooms during study, more methodology of teaching physics, better

methodology education for university teachers and more pedagogy and psychology courses.

Reference

Baranović, Branislava i sur. (2006): Nacionalni kurikulum za obvezno obrazovanje u Hrvatskoj: različite

perspektive, Zagreb, IDI

Cindrić, Marina i sur. (2009): Studij fizike - Bologna, Red predavanja, (23. ožujka 2010. dostupno na

http://www.phv.hr/studiifizike/RedPredavanjaPMF0910-20090902.pdf)

Evans, Linda (1998): Teacher morale, job satisfaction and motivation, London, PCP

Hattie, John A.C. (2009), Visible learning, London and New York, Routledge

McKinsey/Company (2007),//0w the \vorlds best-performing school svstems come out on

top,( 23. ožujka dostupno na:

http://www.mckinsev.coni/locations/UK Ireland/~/media/Reports/UKI/Education report.ashx)

Palekčić, Marko (2008): Odgojne znanosti, yoL10,br.2,p.403-423, Uspješnost i/ili učinkovitost obrazovanja

nastavnika,Zagreb,

Rijavec, Majda i sur. (2008): Pozitivna psihologija, Zagreb, IEP-D2

Rister, Damir (2008): G1REP-EPEC Conference: Frontiers inphysics education 2007, p.433-439,Elementary school

pupils' and teachers' perspectives on physics as school subject, Rijeka,

Student Projects in Chemistry and Ecology (Field work)

Zoran Weihnacht, Šonja Rupčić Petelinc

Prirododslovna škola Vladimira Preloga, sonia.petelinc@vip.hr. weihnachtz@.vahoo.com

Introduction

The field work curriculum comprises of the knowledge acquired in other subjects:

Chemistry: sampling method, analysis of soil, water samples in the nature and school Iaboratory.

Biology: study and analysis of plant and animal life, especially of the protected plant and animal species.

- Geography and Geology: determination and identification of the geographical features, determination of soli

type and composition.

Water is one of the most important raw materials. It is unevenly distributed over space and time. It has become a

limiting factor on economic and socail growth. As the demand for fresh water is constantly climbing, it is necessary

67

to continua!ly monitor and assess vvater quality, as well as economize and regulate its use in order to proteci its

sources.

Educational objectives

Interdisciplinary approach of teaching linked theoretical knovvledge acquired to the practical applications in

the field.

Noticing the essential characteristics of field work, techniques and methods as well as individua! and team

work.

Based on the data obtained, determine the essential and characteristic parameters for the preservation of

ecosystems in which measurements are made.

Students recognize the necessity of linking theoretical knowledge and practical application of the same

during the execution of field measurements.

From the concrete results of the measurements the students are finding positive as well as negative effects

of human activities on the environment.

Measured data should refer students to propose solutions and measures to reduce and completely eliminate

the effects of human activities on the environment

Methods

We have tasted the quality of 180 samples of surface vvater, spring vvater and drinking vvater from the

following areas: Medvednica mountain, Samobor mountains, mountainous region of Gorski kotar, hinterland of

Rijeka, mountainous region of Lika. Phvsical and chemical analvsis of vvater samples vvas carried out in school

laboratories. The follovving parameters vvere measured, pH factor and conductivity. Ammonia, nitrate, nitrite, and

iron content vvas determined by UV-VIS spectrophotometry. Chloride ions were determined by titration using the

Mhor method.

Results

The pH factor is simply a way of expressing the amount of aciditv, i.e. alkalinity of a solution. Unpolluted

waters have a pH under 7, because diluted carbon dioxide makes them mildly acid. Hovvever, if water is polluted

vvith detergents, the pH value vvill be above 7.

Nitrogen appears in nitrate form. It can be found in rain, snovv, fog, but it also occurs during the

decomposition of organic material in soil and sediments. When artificial fertilizers are applied in agriculture, the

level of nitrogen in soil and vvater increases. Nitrogen vvashes out of the soil during heavy rains and is carried directly

to rivers, lakes and seas. An increase of nitrogen concentration can result in excessive grovvth of algae and other

vvater plants, vvhich can induce a change in the smeli and taste of drinking vvater, causing health problem. An

increase of nitrogen in lakes and coastal vvaters is mostly due to the inflovv of sevver and vvaste vvaters.

Most vvaters contain a concentration of 10-30 mg/L of chloride ions. Mountain vvaters, vvhose sources lie in

granite masses, contain less then 10 mg/L. Large chloride quantities in natural vvaters vvhose geological origin can

68

not be determined are mostly caused by industrial waste \vaters or animal waste. Such polluted \vaters usually

contain a chloride concentration of 50-200 mg/L.

Iron is an essential mineral that belongs to micronutrients together with manganese, copper, zine,

molybdenum, cobalt and boron.

Water sample

pH value

K/mS cm1

cCNH^/mgL1

c(NO2)/mgL'

c(N03)/mgL'

c(Cl)/mgL'

c(Fe3+)/mgL'

Dobra river

(Gorski kotar

region)

7,71

304

0,00

0,00

4,00

0,00

0,02

Mrežnica river

(Karlovac

county)

7,37

361

0,00

0,00

4,00

0,00

0,04

Lake Kozjak

(NP Plitvička

jezera)

8,36

290

0,00

0,00

0,00

2,00

0,00

Bregana river

(Samobor

mountains)

8,43

326

0,00

0,00

4,00

13,99

0,00

Gacka river (NP

velebit)

8,60

305

0,00

0,00

0,00

13,29

0,00

Conclusions

The quality of vvater samples gathered in close proximity of urban areas has been affected by agricultural

chemicals, sewage waters and industrial waste. Although no greater pollution has been discovered, there is cause for

concern.

No significant vvater pollution has been detected in non-urban areas.

Reference:

• S. Tedeschi, Zaštita voda, HDGI, Zagreb, 1997, p. 23., 25., 33., 36., 64.

• D. A. Skoog, D. M. West, F. J. Holler, Osnove analitičke kemije, Školska knjiga, Zagreb, p. 489

Ispitivanje kvalitete vode i životnih uvjeta u rijeci Bosut

Rad izradili učenici: Ivan Kelava i Filip Čavar

Mentori: Ozrenka Meštrović, prof. i Dario Dragun, prof.

Osnovna škola „A. G. Matoš", Ohridska 21, Vinkovci

email: dario.dragunl@skole.hr, ozrenka.mestrovic@skole.hr

Nema ništa bolje od vode. Ovu činjenicu ustanovio je prije otprilike 2500 godina grčki pjesnik Pindar. Što

ovu tekućinu čini uistinu tako posebnom? Odgovor se zna već dugo: postoji vrlo bliska veza između vode i svakog

oblika života. Voda otapa mnogo tvari neophodne za život, a u otopljenom stanju tvari se mogu lakše transportirati

do svake točke u organizmu. Voda zauzima približno 71% ukupne površine zemlje, zato planet Zemlju zovemo još i

„vodeni planet". 7% ukupne količine vode na Zemlji otpada na rijeke, jezera i potoke '. Bosut je rijeka koja gotovo

69

da i ne teče. U narodu kažu: u kojem smjeru puše vjetar, u tom smjeru Bosut teče. Stari Rimljani su znali reći kako u

svom carstvu imaju rijeku koja dopodne teče na jednu stranu, a popodne na drugu, a pri tome su mis l i l i na Bosut.

Bosut je rijeka bez izvora jer nastaje spajanjem Bida i Berave i ponekad tako mirno teče da se i malim vjetrom voda

pokrene u jednom i l i drugom smjeru. Zbog slabe protočnosti, sklonija je zadržavanju štetnih tvari. Stoga Bosut po

svojim obilježjima možemo svrstati u vode stajaćice. Najveći zagađivač Bosuta do 2005. godine bila je gradska

kanalizacija koja je izgrađena 1964. godine i sve do 2005. godine direktno se ulijevala u rijeku. Tek 2005. godine

sagrađen je kolektor za pročišćavanje otpadnih i fekalnih voda. Tvornica za preradu kože u Vinkovcima bila je

najveći zagađivač vode uz gradsku kanalizaciju. U Bosut je ispuštala sve otpadne kemikalije bez prethodnog

pročišćavanja stoje uzrokovalo pomor ribe. Do razvoja kanal izacijske infrastrukture tvornica za preradu kože bila ja

najveći zagađivač. Zbog slabog toka rijeke pomor ribe osim što se širio nizvodno, širio se i uzvodno od grada.

Najveći pomor ribe se dogodio 1998. godine na potezu od centra grada pa uzvodno do Sopota, zbog velike količine

organskog otpada koji se raspadao na dušične spojeve NO2, NO3 i amonijak pri čemu se trošila velika količina

otopljenog kisika iz vode i riba nije mogla opstati 2. Tijekom 1984. godine gradio se most preko rijeke Bosut koji je

spajao staru jezgru grada s naseljem preko rijeke. Te godine razina vode spuštena je za l metar zbog gradnje mosta i

zidanja obale. Kako je već tada bilo jako puno mulja bilo je pogodno za razvoj biljaka. Bujanjem bilja, voda je bila

topla, udio otopljenog kisika se smanjivao. Odumrle biljke trunule su na dnu rijeke i dodatno trošile kisik. Bio je to

jedan od većih pomora ribe u kojem je stradalo približno 90% ribe u Bosutu2. Jedno od važnijih zagađenja je i

ulijevanje pesticida i insekticida u rijeku. Naime, kada poljoprivredni avioni zaprašuju polja pesticidima nerijetko ti

pesticidi dolaze i u vodu gdje uništavaju dio živog svijeta. Isto tako djeluju i insekticidi kojima se najčešće ljeti i u

jesen zaprašuju šume gdje se komarči razmnožavaju, no sve šume na tom području nalaze se u blizini rijeke. Jedan

oblik opasnog zagađenja je i izlijevanje lokalnih kanalizacijskih odvoda u Bosut. Kada čovjek uzrokuje povećanje

koncentracije određenih tvari u vodi (bilo one prirodno prisutne u većim količinama ili prisutne samo u mikro -

koncentracijama) mijenja ravnotežu i uzrokuje promjene u broju i vrsti organizama.

Materijali: terenska oprema za određivanje iona u vodi (komplet za Analizu vode; Model Educa), termometar,

reagens boce i laboratorijsko posuđe. Metode: vodu smo prikupili na 4 postaje: tri postaje u središtu grada te na

jednoj postaji izvan grada. Uz pomoć gotovih protokola (komplet za Analizu vode, Model Educa) na postajama smo

određivali: pH, temperaturu, alkalitet, udio otopljenog kisika, udio iona (željezo, karbonatni ion, fosfatni ion,

amonijev ion, nitriti, nitrati i magnezij). Prilikom analize glavni cilj bio nam je ustanoviti masu otopljenih tvari u 1L

(mg/L) vode. Pri analizi ostalih parametara slijedili smo standardizirane, zadane protokole za analizu vode (Model

Educa).3 Vrijednosti parametara se određuju subjektivno tj. usporedbom boje uzorka sa bojama na skali, odnosno

pomicanjem uzorka od polja do polja.

Rezultati dobiveni analizom vode sa sva četiri mjesta uzorkovanja su prikazani u slijedećoj tablici.

Analizirani parametri

PH

Fe2+

PO43'

Postaja 1.

7,2

0,075 mg/L

0,6 mg/L

Postaja 2.

7,3

0,05 mg/L

0,5 mg/L

Postaja 3.

7,0

0,075 mg/L

0,5 mg/L

Postaja

Slakove!

7,0

0,075 mg/L

0,6 mg/L

70

02

NO3"

NO2"

NH,+

Tvrdoća vode (Ča/Mg)

Karbonatna tvrdoća COj2'

Temperatura vode

(pri uzorkovanju)

Temperatura vode

(pri analizi)

5 mg/L

6,5 mg/L

0,075 mg/L

0,2 mg/L

4,2 mg/L

3 10 mg/L

9° C

23° C

8 mg/L

5,0 mg/L

0,2 mg/L

0,2 mg/L

4,3 mg/L

250 mg/L

8° C

22° C

6 mg/L

7,0 mg/L

0,2 mg/L

0,3 mg/L

5,5 mg/L

303 mg/L

8° C

24° C

5 mg/L

6,5 mg/L

0,075 mg/L

0,1 mg/L

4,1 mg/L

321 mg/L

10° C

23° C

Analizom smo smjestili vodu Bosuta u III., odnosno IV. kategoriju kvalitete te smo poprilično točno uspjeli odrediti

koncentracije promatranih parametara. Rezultatima smo zadovoljni jer smo usporedbom podataka dobivenih u našoj

analizi i onima dobivenima u pravom laboratoriju4 uvidjeli daje komplet za analizu vode pouzdan te ćemo ga sa

sigurnošću koristiti u istraživanjima koja slijede (biološka i kemijska analiza vode te popis biljnih i životinjskih vrsta

na Bosutu).

1 Đikić, D. i sur. (2001): Ekološki leksikon, O.P. Springer (ur.); Barbat, Zagreb2 Tugomil Štefanić - usmeno priopćenje (Dr. Štefanić se bavi analizom Bosuta gotovo 40 godina svoga

života te je veliki stručnjak po tom pitanju). Audio snimka; 20093 Kerovec, M. i sur. (2002): Ekologija životinja s biocenologijom, Interna skripta Zoologijskog zavoda,

Biološki odsjek - PMF, Zagreb4 Hrvatske vode: Laboratorij za vodu - rezultati analize vode za 2008. godinu; Slavonski brod

Testing of water quality and living conditions in the river Bosut

This is a student project of Ivan Kelava and Filip Čavar

Ozrenka Meštrović i Dario Dragun

Primary school: ,,A. G. Matoš", Ohridska 21, Vinkovci

dario.dragun l (5iskole.hr. ozrenka.mestrovic@.skole.hr

There is nothing better than water. This fact was established 2500 years ago by the Greek poet Pindar. What

really makes this l iquid so special? The ansvver has been knovvn for a long time: there is a very close connection

betvveen the vvater and ali forms of life. Water dissolves many substances necessary for life, and these substances can

be easily transported to any part of the body. Water occupies about 71% of the total area of planet Earth, because of

71

that our planet is called the "\vater planet". 7% of the total amount of vvater on Earth is in the rivers, the lakes and the

streams1. Bosut is a river that has almost no flow. The people say "in vvhich direction the wind is blowing in that

direction Bosut is flovving". The ancient Romans used to say that there is a river in their empire that flows to one side

in the morning and to the other in the afternoon. Bosut is a river without a spring because it is created by merging of

rivers Biđ and Berava. Due to the low flovv, Bosut tends to retain pollutants. Therefore, by its nature Bosut can be

marked as a standing vvater. Bosut biggest polluter by 2005 was the city sevvage. It vvas constructed in 1964 and until

2005 the sewage vvater poured directly into the river. In 2005 a collector vvas built for the vvaste and sevvage. Besides

the city sewage system, leather factory in Vinkovci vvas the biggest polluter of vvater. It emitted the chemicals into

Bosut vvithout any waste pre-treatment and thus caused the massive fish mortality. Due to lovv river flovv fish plague

spread dovvnstream and upstream of the city. The highest mortality of fish occurred in 1998 due to the large amounts

of organic vvaste decomposed to nitrogen compounds NO2, NO3 and ammonia and the process consumed a large

amount of dissolved oxygen from the vvater so the fish could not survive. In the 1984 the nevv bridge across the river

vvas built. Water level vvas lovvered by l meter for the purpose of building bridges and building the coast. At that

time there vvas already a lot of sludge vvhich vvas suitable for plant development. Due to the proliferation of plants,

the vvater vvas vvarm, the proportion of dissolved oxygen vvas reduced. It vvas one of the biggest fish kills vvhich killed

approximately 90% of fish in Bosut2. One of the main pollutants are pesticides and insecticides that are used

throughout the year on the farming fields near the river and in the nearby vvoods. One form of pol lut ion and

hazardous spills is from local sevvers into Bosut.

When a man causes an increase in the concentration of certain substances in vvater (either those naturally present in

large quantities or those present only in micro - concentrations) it changes the balance and causes changes in the

number and type of organisms.

Materials: field equipment for determination of ions in vvater (vvater analysis kit, Model Educa), thermometer,

reagent bottles and laboratory vvare. Methods: vve collected the vvater at 4 stations: three stations in the city centre

and a location outside the city. With the help of ready-made protocol (vvater analysis kit, Model Educa) vve

determined at the stations: pH, temperature, alkalinity, dissolved oxygen share, the share of ions (iron, carbonate ion,

phosphate ion, ammonium ion, nitrite, nitrate and magnesium). During the analysis the main goal vvas to determine

the mass of substances dissolved in l L (mg / L) of vvater. In the analysis of other parameters, vve follovved the

standard, default protocols for vvater analysis (Model Educa)3.

The values of parameters are determined subjectively by comparison of colour pattern vvith the colours on the scale

and by moving the pattem from field to field.

The results obtained by analyzing the vvater from the four sampling sites are shovvn in the follovving table.

Analised parameters

PH

Fe2+

po43-

Location 1.

7,2

0,075 mg/L

0,6 mg/L

Location 2.

7,3

0,05 mg/L

0,5 mg/L

Location 3.

7,0

0,075 mg/L

0,5 mg/L

Location

Slakovci

7,0

0,075 mg/L

0,6 mg/L

72

02

N03-

NO2"

NH,+

Water hardness (Ča/Mg)

Carbonate hardness CO32"

Water temperature

(sampling)

Water temperature

(during analisis)

5 mg/L

6,5 mg/L

0,075 mg/L

0,2 mg/L

4,2 mg/L

3 10 mg/L

9° C

23° C

8 mg/L

5,0 mg/L

0,2 mg/L

0,2 mg/L

4,3 mg/L

250 mg/L

8° C

22° C

6 mg/L

7,0 mg/L

0,2 mg/L

0,3 mg/L

5,5 mg/L

303 mg/L

8° C

24° C

5 mg/L

6,5 mg/L

0,075 mg/L

0,1 mg/L

4,1 mg/L

321 mg/L

10° C

23

Analysis placed the water of the river Bosut in the third (III.) and fourth (IV.) category of quality and we were quite

able to accurately determine the concentration of the observed parameters. We are pleased with the results because

we compared the data obtained in our analysis and those obtained in the laboratorv4 and realized that the water

testing kit is reliable. We will certainly be using it in the researches that will follow (biological and chemical analysis

of vvater and a list of plant and animal species in Bosut).

1 Đikić, D. i sur. (2001): Ekološki leksikon, O.P. Springer (ur.); Barbat, Zagreb2 Tugomil Štefanić - oral communication (Dr. Štefanić analyzes Bosut nearly 40 years of his life and is a great

expert on this issue). Audio recording; 20093 Kerovec, M. i sur. (2002): Ekologija životinja s biocenologijom, Interna! script Zoologijskog Institute,

Department of Biology - Faculty of Science,4 Hrvatske vode: Laboratory for water - vvater analysis results for 2008. year; Slavonski brod

Razumijevanje koncepta kovalentne veze

'Marija Lozo, 2Roko Vladušić

'OŠ oca Petra Perice, Zelenka bb, Makarska2Prirodoslovno-matematički fakultet Sveučilišta u Splitu

mariialozo24@.gmail.com vladusic@pmfst.hr

Problem nerazumijevanja elektrostatske prirode kemijskih veza prisutan je u različitim

obrazovnim sustavima. Tako je, primjerice, kod usvajanja znanja o kovalentnoj vezi uočeno

nerazumjevanje koncepta elektronegativnosti, nesposobnost da se odredi polarnost pojedinih

73

There vvere 612 secondary school students from various grades of secondary schools involved in the main study. It

took 20-40 minutes for the participating students to complete the questionnaire in the survey (Chiu, et al. submitted).

Students' conceptions of models are listed below:

/. A model is a replica, and to be viewed as reality: 79.2% students considered models as replicas of specific things,

46.6% of students thought that the structure, nature and relations of a model need full correspondence to specific

things.

2. The composition of models: 30.2% students did not consider models to be symbols, 25.8% students did not think a

model can be a process, and 10.8% students did not think a model can be a concept.

3. The functions of models: 39.2% of students did not think that the functions of models can be for predicting

development of things or phenomena for future use, 16.3% of students did not consider the functions of models can

be for producing new ideas, and 12.1% students did not consider that the functions of model can be used for

reasoning. Apparently, instruction on understanding the nature of models was underdeveloped in many areas in

science education.

C. Bridging the gap betvveen research and practice — How to teach

Study 1: Teaching chemistry with analogies

A study (Chan, 2002) conducted in the presenter's research lab was designed to elaborate on the role of multimedia

and multiple representations in learning scientific concepts and to investigate the effectiveness of dynamic

representations on students' learning. Chan (2002) developed a computer-based set of dynamic analogies. The

research investigated 53 8lh graders who were learning chemical equilibrium. The students vvere randomly assigned

to three groups: control group (C); analogy and instruction group (A); and analogy, instruction, and animation with

dynamic analogy group (D). Six target students vvere chosen from each group to be intervievved for their conceptual

change via learning vvith model-based animation and dynamic analogy instruction. The results show that the

students' performance in the three groups was not significantly different at the pretest. Hovvever, the post-test

revealed both analogy group A and dynamic analogy group D outperformed the control group C and that D group

performed better than A group on the gained scores. The tvvo groups did better than the control group on the post-test

as vvell as on on the retaining test. Betvveen analogy group A and dynamic analogy group D, there vvere significant

differences on the pretest and the post-test.

Study 2: Teaching chemistry \vith Multi-representation activities

The purpose of this study was to investigate secondary students' mental models of electrochemistry before and after

a series of modeling activities and hovv their mental models vvere changed using various teaching strategies (Chiu &

Chung, 2010). The research design was mainly adopted the idea about model-based approach for teaching students

the concepts of electrochemistry. The multiple model-based approaches covered gestures, concrete models,

language, visual, role plays, and symbolic representations in teaching-learning sequences. Three groups vvere

designed to ansvver our research questions. We also used the dynamic formative assessments to collect data about

kovalentnih spojeva, pogrešni stavovi da su nepolarne molekule građene samo od atoma jednake

i l i približno jednake elektronegativnosti te razmišljanja da broj valentnih elektrona i prisutnost

nepodijeljenih elektronskih parova određuju polarnost molekule (Peterson i ostali, 1989; Harrison

i Treagust, 1996; Boo 1998).

Uvažavajući navedene spoznaje provelo se istraživanje čiji je cilj bio utvrditi značajke

poznavanja i razumijevanja koncepta kovalentne veze među srednjoškolskom populacijom i

studentima te otkriti uzroke eventualnih nejasnoća.

Istraživanje se baziralo na detaljnom ispitivanju učenika dviju gimnazija i studenata

Prirodoslovno-matematičkog fakulteta primjenom kvalitativne metode intervjua.

Zaključeno je da su učenički koncepti kovalentne veze popraćeni brojnim nejasnoćama i

zabludama. Uočene su velike razlike u usvojenosti pojedinih segmenata znanja između učenika

dviju gimnazija. Utjecaj nastavnika kemije na takve rezultate je neosporan. Osim

nerazumijevanja pojmova i koncepata koje su trebali usvojiti prema tekućem programu, pojedini

učenici su iskazali poteškoće i prilikom objašnjavanja osnovnih pojmova kao što su građa atoma,

određivanje brojnosti subatomskih čestica te razlikovanje ionske i kovalentne veze. Uočena je

podudarnost nejasnoća i zabluda hrvatskih učenika s onima do kojih su došli istraživači u drugim

zemljama. Nerazumijevanja pojedinih kemijskih koncepata iskazana na gimnazijskoj razini

zadržavaju se i na studiju. Izuzev nekolicine studenata prve godine koji su nedavno položili

kolegij Opća kemija I, preostali studenti prve i pete godine mahom pokazuju neusvojenost

pojmova s tercijarne razine.

Razvidno je da mali broj učenika, odnosno studenata, pokazuje usustavljeno znanje.

Zabrinjavajuća je spoznaja da uočena pojavnost nije odlika nekolicine ispitanika već je široko

rasprostranjena unutar ispitivane populacije.

Literatura:

1. R. F. Peterson,-D. F. Treagust, P. Garnett, Development And Application Of A Diagnostic

Instrument To Evaluate Grade-11 And Grade-12 Students' Concepts Of Covalent Bonding And

Structure Following A Course Of Instruction, Journal of Research in Science Teaching, 26

(l989), 301-314.

2. A. G. Harrison, D. F. Treagust, Secondary Students' Mental Models of Atoms and Molecules:

Implications for Teaching Chemistrv, Science Education, 80 (1996),509-534.

74

3. H. K. Boo, Students' Understanding Of Chemical Bonding And Energetics Of Chemical

Reactions, Journal of Research in Science Teaching, 35 (1998), 569-581.

Utječe li oblik tessta iz kemije na uspješnost učenika na testu?

Željana Fredotović, Višnja Vuko

Prirodoslovno matematički fakultet, Split, zcliana.fredotovic(2)hotmail.com. visniavuko@vahoo.com

Provedeno je empirijsko istraživanje na 49 učenika dvaju osmih razreda osnovne škole. Istraživanje je temeljeno na

dva različita, ali usklađena testa (otvorenog tipa i višestrukog odabira) koja ispituju razumijevanje i poznavanje istih,

precizno određenih pojmova i procesa koji obuhvaćaju nastavni sadržaj kemije sedmog i osmog razreda. Testovi

sadrže po petnaest pitanja koja su pripremana i međusobno usklađena strogo prema zakonima izrade testova

(napomena: ne možemo objektivno suditi o njihovim karakteristikama jer ih nismo prethodno proveli na jako

velikom uzorku, stoga ne možemo govoriti o standardiziranim testovima). Učenicima su data oba testa na rješavanje

i to na način da su prvo rješavali test otvorenog tipa, a potom test višestrukog izbora. Cilj je bio prikupiti iskustvene

podatke radi utvrđivanja eventualnih razlika u rezultatima navedenih testova. Indukcijskom metodom i statističkom

analizom pokušali smo potvrditi postavljenu nul-hipotezu koja glasi „Različiti tipovi testova kojima se ispituje isto

područno znanje ne rezultiraju različitim ishodima". Motiv za ovo istraživanje bili su modeli vanjskog vrednovanja

(ispit iz kemije s državne mature) koji se baziraju na zadatcima višestrukog izbora, za što nismo sigurni da (posebno

u kemiji) adekvatno reflektiraju učenikovo znanje, posebno više razine istog; analizu, evaluaciju i sintezu.2 Testirani

učenici pokazali su znatno veću uspješnost (65%) na testu višestrukog odabira nego na testu otvorenog tipa (35%).

Pokazalo se da test otvorenog tipa traži od učenika veći kognitivni napor i testira sposobnost pismenog izražavanja

koja se, u našem istraživanju, pokazala izrazito slabom.

Literatura:

1. B. S. Bloom, Persistent Methodological Questions in Educational Testing Rewiew of Research

in Education, 1999, 24: 393-446.

2. B. S. Bloom: Taxonomy of Educational Objectives: The Classification of Educational Goals,

New York, 1956, pp. 201-207.

Obrazovanje kemijskih tehničara

Zorica Popović, Prirodoslovna škola Vladimira Preloga, Zagreb

75

U Prirodoslovnoj školi Vladimira Preloga, kemijski tehničari obrazuju se već 65 godina. Program se tijekom

vremena mijenjao, prilagođavajući se potrebama tržišta. Tako su u prvim godinama postojanja škole više pažnje

posvećivalo kemijskoj tehnologiji jer je u Zagrebu, u to doba, bila vrlo snažna kemijska industrija: Chromos-Katran-

Kutrilin, Pliva, Labud... Čak je bilo vrlo izražajno večernje obrazovanje prekvalifikacije raznih struka u kemijske

tehničare.

Poslije domovinskog rata, kemijska industrija gotovo da više i ne postoji. U obrazovni sustav Republike

Hrvatske vraćaju se programi gimnazije i kemijska struka doživljava svoj lagani pad.

Stoga sada obrazujemo samo dva paralelna razreda. Pored redovnog programa, učenicima se nude izborni

programi.

U redovnom programu, učenici u prvom razredu, slušaju Opću kemiju s vježbama. U teorijskom dijelu uče:

tvari, atom, periodni sustav elemenata, kemijske veze, strukture molekula, kristale, osnove računanja u kemiji,

otpine, kiseline i lužine, kiselo-bazni indikatori, neutralizacija, hidroliza soli te uvod u elektrokemiju i redoks

reakcije. Na laboratorijskim vježbama u početku se učenici uče kako raditi u laboratoriju, a potom se, izvođenjem

vježbi, prati teorijsko gradivo.

U izbornom programu učenici najčešće, u prvom razredu, izabiru Osnove ekologije i Izabrani kemijski

procesi. Predmet Osnove ekologije bazira se na interdisciplinarnom pristupu gdje se isprepliće biologija, matematika,

kemija, ekonomija... Cilj je upoznati učenike s važnošću očuvanja okoliša. Stoga se ovaj predmet realizira i na

terenskoj nastavi, počevši od Botaničkog i Zoološkog vrta u Zagrebu, pa do drugih karakterističnih područja diljem

Hrvatske.

Izabrani kemijski pokusi nadopunjuju gradivo opće kemije i, kako samo ime kaže, interesantnim kemijskim

pokusima koje se na redovnoj nastavi, zbog vremenske ograničenosti, ne mogu provesti.

U drugom razredu je Anorganska kemija s vježbama. Samo ime govori o programu. Nastavljaju se predmet

Izabrani kemijski pokusi, ali se nudi još jedan izborni program: Kemijski procesi u okolišu. Taj program

nadopunjava gradivo anorganske kemije i opet nudi rad u prirodi u obliku terenske nastave.

Anorganska kemija dopunjava se i Analitičkom kemijom s vježbama, koju učenici prate tijekom ovog

razdoblja školovanja.

Treći razred obiluje sadržajima iz kemije: Organska kemija s vježbama, Fizikalna kemija, Tehnološke

operacije s vježbama. Teorijski dio organske kemije sadrži: karakteristike C-atoma, ugljikovodici, organski spojevi s

kisikom, organski spojevi sa sumporom, organski spojevi s dušikom, uključen je i kemijski račun. Na vježbama se

uče tehnike rada u organsko kemijskom laboratoriju, a poslije se izvode sinteze organskih spojeva. Fizikalna kemija

obrađuje agregacijska stanja tvari, otopine i svojstva otopina (nadopunjujući dotadašnje spoznaje o otopinama),

termokemija, elektrokemija.

Tehnološke operacije su ostatak nekadašnje pozamašne tehnologije u struci kemijskih tehničara. Sada se

samo obrađuju oni tehnološki procesi koji se i dalje primjenjuju u praksi, a vježbe se izvode u pojednostavljenim

reaktorima.

Tijekom druge i treće godine obrazovanja, učenici imaju Stručnu praksu na kojoj primijenjuju ono što su

tijekom školovanja naučili: izrađuju školsku kredu za potrebe škole, eko-mrežice, tekući sapun, demineraliziranu

76

vodu. Svoje proizvode razmjenjuju s učenicima drugih škola. Isto tako pomažu u pripremi u laboratorijima i

posjećuju razne institucije u Zagrebu: izložbe i manifestacije u Tehničkom muzeju, institute. Ovaj predmet se ne

ocjenjuje numerički.

U trećoj godini, od izbornih programa se nudi: Mjerenja u okolišu, Kemija i nutricionizam.

Četvrti razred je i priprema za završetak školovanja. Kemijski tehničari izrađuju i brane završni rad. Oni,

koji žele na studij, polažu Državnu maturu.

Tijekom četvrtog razreda učenici imaju Biokemiju s vježbama. Taj program je vrlo rijedak obrazovni

program u našoj domovini. U njemu učenici uče osnovne spojeve koji grade organizam: lipide, ugljikohidrate,

aminokiseline, proteine, vitamine..., ali i enzimsku kinetiku. Ovaj program je dobar za izvođenje projektne nastave,

pa smo se do sada bavili kukuruzom (kroz četiri generacije učenike), krumpirom, graškom, žitaricama, grahoricama.

Neki od ovih radova bili su objavljeni u časopisima, a sudjelovali smo i na kongresima kemičara Hrvatske.

Nakon trećeg razreda, u četvrtom se rade Vježbe iz fizikalne kemije: potenciometrija, konduktometrija,

Nernstov zakon, refraktometrija, polarimetrija. Od izbornih programa nudi se Povijest kemije, Izabrani tehnološki

procesi, Toksikologija, i za učenike, vrlo privlačna Forenzična ispitivanja.

Sve, u laboratoriju izvedene vježbe, učenici moraju obraditi u laboratorijskom dnevniku. To mogu učiniti i

PC-em, jer imaju, nakon Informatike u 1. i 2. razredu, i Primijenjenu informatiku u 3. i 4. razredu gdje uče obrađivati

podatke, raditi skice, grafove, tablice, fotografije.

Naši učenici sudjeluju na raznim natjecanjima i postižu zapažene rezultate. To su, prije svega Državna

natjecanja iz kemije, na kojima svake godine imamo nekoliko učenika. Kako radimo puno vježbi, naši učenici

uglavnom sudjeluju u prezentacija svoga rada i istraživanja u kemiji.

Sudjelujemo i na međunarodnom natjecanju Grand Prix Chemique od 2003. godine. Bili smo domaćini

ovog natjecanje 2007. godine.

Mnogi naši učenici su završili fakultete, neki postali doktori znanosti i sveučilišni profesori s kojima i

danas surađujemo. Lijepo je doći u neku instituciju i tamo susresti bivšeg učenika koji radi kao kemijski tehničar,

asistent na fakultetu ili doktor znanosti, docent...

Obrazovanje ekoloških tehničara

Mara Husain, Zorica Popović, Prirodoslovna škola Vladimira Preloga, Zagreb

77

Ove školske godine, svoje srednjoškolsko obrazovanje upravo će završiti deveta generacija ekološkog

tehničara.

Program je prilagođen suvremenim potrebama zaštite prirode i obrade otpada. Cilj je bio pokrenuti

programe iz zbrinjavanj kućnog i industrijskog otpada otpada u gradovima (Zagreb, Rijeka), poljoprivredna

ekologija (Osijek), zaštita mora i ekologija mora (Split). Inicijator programa bio je ravnatelj naše škole dipl. inž.

kemije Zlatko Stic, koji je završio srednjoškolsko obrazovanje kao kemijski tehničar.

Sadržaji programa prilagođeni su tako da učenici, nakon završenog srednjoškolskog obrazovanja, mogu

raditi kao rendžeri u parkovima prirode i nacionalnim parkovima, mogu se zaposliti u zbrinjavanju otpada i l i

studirati.

Tijekom prve godine obrazovanja, učenici imaju Opću kemiju s vježbama, po programu sličnom kemijskim

tehničarima.

U drugoj godini učenici imaju Anorgansku kemiju, ali umjesto vježbi imaju Svojstva staništa (vježbe) u

kojima se obrađuju karakteristike staništa tako da su teme odabrane iz područja zrak, voda, tlo. Tijekom ove godine

obrazovanja, učenici počinju proučavanje organske kemije: ugljikovodici.

Treća godina nudi predmet Kontrola i zbrinjavanje otpada. To su vježbe u trajanju od 5 sati gdje učenici

počinju učiti o raznim tvarima: kako ih identificirati i zbrinuti. Uglavnom su to kvalitativna ispitivanja. U ovoj godini

se nastavlja Organska kemija s vježbama u kojo se uče ostali organski spojevi i izvode vježbe slično kao kod

kemijski tehničara samo što se više pažnje pridaje utjecaju na okoliš pojedinih spojeva i njihovo zbrinjavanje.

. Tu počinje proučavanje Fizikalne kemije, opet slično kao kod kemijskih tehničara.

U četvrtoj godini nastavlja se program Kontrola i zbrinjavanje otpada u trajanju od 6 sati, ali su ovaj put

analize kvantitativne: gravimetrija i volumetrija, te analiza uzoraka prikupljenih na terenu.

Ovaj predmet se nadopunjava Instrumentalnim metodama u zaštiti okoliša, gdje se analize provode

instrumentima: spektroskopskim metodama, konduktometrijski, polarimetrijski, pH-metrijski, refraktometrijski...

U ovoj godini se proučava i Biokemija s vježbama u manjem obimu nego stoje to kod kemijskih tehničara.

Specifičnost programa je stručna praksa koja se obavlja diljem Hrvatske u nacionalnim parkovima i

parkovima prirode, raznim ustanovama... Do sad su naši učenici prošli terensku nastavu u:

• Zagreb (Botanički i Zoološki vrt i Maksimir, Medvednica),

• Istra (Briuni, Baradina. Limski zaljev, Motovunska šuma, Hum, Pula),

• Gorski kotar (Vražji prolaz, Klek, Kamčnik, Risnjak),

• Velebit i Lika ( Gacka, Otočac, Sjeverni Velebit, Paklenica, Krasno),

• Dalmacija i Primorje (Cres-Beli, Mali Lošinj, Telaščica, Zadar, Nin, Kornati, Mljet, Dubrovnik-

arboretum),

• Slavonija i Baranja (Papuk, Požega, Osijek, Đakovo, Kopački rit, Ilok, Vukovar),

• Zagorje (Varaždin, Krapina),

• Podravina i sjev. Hrvatska (Đurđevac, Koprivnica, Križevci, Kalnik)...

78

Nakon provedene terenske nastave, prikupljene podatke učenici obrađuju u terenskom dnevniku. Puno je

lijepih fotografija i mnogo divnih uspomena s tih terena.

Naša škola je pokrenula natjecanje ekoloških tehničara na nivou Države u suradnji s Agencijom za

strukovno obrazovanje. Ove škloske godine bit će održano treće po redu natjecanje u programu ekološki tehničar. Na

dosadašnja dva, naši učenici su postigli zapažene rezultate u osvajanju prvih mjesta.

Kao i kemijski tehničar, i ekološki tehničar, mora izraditi i položiti završni rad, a za upis na studij položiti i

Državnu maturu. Prošle godine svi naši učenici ekološki tehničari položili su Državnu maturu.

Prirodoslovna gimnazija

Mara Husain

Prirodoslovna škola Vladimira Preloga, Zagreb, Ulica grada Vukovara 269

Uvođenjem novih smjerova obrazovanja: kozmetičar, ekološki tehničar i prirodoslovna gimnazija uslijedila

je promjena imena škole iz Kemijska i geološka tehnička škola u Prirodoslovna škola Vladimira Preloga.

Posebnost obrazovanja u smjeru prirodoslovne gimnazije je u naglasku na prirodoslovlje, koje se tijekom

sve četiri godine obrazovanja, realizira individualnim izvođenjem vježbi.

Predmet Kemija s vježbama učenicima na taj način teoretske sadržaje približava i olakšava savladavanje

samostalnim izvođenjem vježbi. Teorijski dio programa, prati program ostalih prirodoslovnih gimnazija, ali vježbe

su s dva sata tjedno, ono što ovaj program čini specifičnim.

Tijekom prvog razreda uče se osnove kemije na teoriji, a na vježbama, nakon uvođenja u laboratorijski rad,

upoznaju se karakteristike važnijih kemijskih elemenata i njihovih spojeva kroz interesantne eksperimente.

U drugom razredu proučava se fizikalna kemija, čiji se sadržaji prate i laboratorijskim vježbama.

U trećem razredu proučava se anorganska kemija, a na vježbama se vrše analize.

Četvrti razred je organska kemija i sadržaj vježbi prati ovaj program kemijskim sintezama organskih

spojeva.

Učenici rezultate laboratorijskih vježbi obrađuju u laboratorijskom dnevniku.

Od ove školske godine, obrazovnju u programu prirodoslovne gimnazije, pridružio se i jedan razred

sportaša, tzv. sportska gimnazija. Sadržaj programa kemije identičan je sadržaju u svim smjerovima, samo se

raspored pohađanja nastave prilagođava sportašima , kako bi mogli i trenirati.

Prošle godine, naši gimnazijalci postigli su zapažen uspjeh na Državnoj maturi. I oni sudjeluju na Državnim

natjecanjima iz kemije i kao kemijski tehničari skloniji su istraživačkom radu.

Suradnju svih naših učenika teško je razdvojiti. Posebno je to izraženo u dramskoj, literarnoj i pjevačkoj

aktivnosti.

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Priprava koloidnih sustava i kiselinsko-bazne ravnoteže

Mirela Pavić i Nenad Judaš

Kemijski odsjek, Prirodoslovno-matematički fakultet, Sveučilište u Zagrebu

mirepavi@gmail.com iudas@chem.pmf.hr

Koloidni sustavi su jako rašireni u prirodi i susrećemo se s njima u svakodnevnom životu. Stoga je bitno

upoznati njihova svojstva i neke načine primjene koloida. Smjese tvari u kojima su čestice jedne tvari dispergirane u

drugoj tvari zovemo disperzni sustavi. Disperzni sustavi mogu biti u bilo kojem agregacijskom stanju. Na temelju

veličine čestica dispergirane tvari, disperzne sustave dijelimo na suspenzije, koloidne sustave (koloide) i prave

otopine. Suspenzije su disperzni sustavi koji imaju najveće čestice i te čestice predstavljaju zasebnu fazu. Koloidni

sustavi imaju nešto manje čestice koje su dovoljno velike da se smatraju zasebnom fazom, ali se kinetički ponašaju

kao molekule. Upravo su zbog toga koloidi jako zanimljivi.

Važno svojstvo koloida je velika površina dispergiranih čestica i zbog toga je njihova površinska energija

velika, pa je za očekivati da su u energijskom smislu nepostojani. Koloidni sustav se stoga stabilizira nakupljanjem

čestica u veće nakupine - koagulira. Međutim, koloidni sustavi često mogu biti i stabilini u duljim vremenskim

periodima. U koloidnom sustavu čestice su dispergirane u obliku micela koje mogu biti hidrofobne ili hidrofilne.

Hidrofilne čestice će na sebe vezati molekule vode koje će onemogućiti njihov međusobni dodir, a time i

koagulaciju. Hidrofobne čestice će odbijati molekule vode, ali na svoju površinu će vezati ione koje ima u otopini,

prvenstveno one koje i same sadrže. Zbog toga vezivanja iona sve će čestice biti jednako nabijene i elektrostatski će

se odbijati, pa neće doći do koagulacije. Ako otopini dodamo ione koji će neutralizirati taj naboj, doći će do

koagulacije. Pokus prezentiran u ovom radu upravo je prikladan za pokazivanje koagulacije koloidnih čestica i

objašnjavanje nabijenosti površine čestica.

Koloidni sustavi su nastavna tema koja se, prema trenutnom nastavnom planu i programu, obrađuje u

sklopu nastavne cjeline Otopine. Koloidni sustavi ne moraju nužno biti otopine (najčešće se pod koloidnom

otopinom podrazumjeva čvrsta tvar dispergirana u tekućini ili tekućina dispergirana u tekućini). Ukoliko je čvrsta

tvar dispergirana u čvrstoj tvari (npr. poludrago kamenje), ako je čvrsta tvar dispergirana u plinovitom disperznom

sredstvu (npr. duhanski dim) ili ako je plin dispergiran u čvrstom disperznom sredstvu (npr. silikagel), to se također

ubraja u koloide. Stoga, ukoliko se koloidi obrađuju unutar nastavne cjeline Otopine, može doći do pogrešnog

shvaćanja pojma koloid, tj. da su koloidi samo sustavi u kojima je čvrsta faza raspršena u tekoćoj.

Ova nastavna tema bi se trebala obrađivati nakon što učenici usvoje Br0nsted-Lowryevu teoriju kiselina i

baza te pojmove: pH-vrijednost, kemijska ravnoteža, povrativa reakcija, konstanta ravnoteže, Le Chatelierov princip.

Tada bi mogli razumjeti i usvojiti točna znanja o svojstvima koloida i uočiti da se oni ne razlikuju od čestica u

suspenziji samo po veličini nego i po svojstvima. Navedena predznanja su posebno korisna prilikom objašnjavanja

velike površine koloidnih čestica, nabijenosti površine koloidnih čestica i koagulacije istih.

Opisivanje kemijskih prmjena simboličkim jezikom - jednadžbe kemijskih reakcija

80

Monika Štetić i Nenad Judaš

Kemijski odsjek, Prirodoslovno-matematički fakultet, Sveučilište u Zagrebu

monika.stetic@gmail.com judas@chem.pmf.hr

Kemija je znanost koja počiva na pokusima. Od pokusa sve počinje, pa je nužno da tako bude i s nastavom

kemije. Na žalost, moramo konstatirati da je danas pokus u nastavi kemije zanemaren, a kad ga i ima onda je

uporabljen na deskriptivnoj razini - pokus najčešće potvrđuje rečeno. Uglavnom se zanemaruje srž pokusa, njegova

prava kemijska narav. A to nije logično, zar ne?

Da bismo opisali kemijske promjene i "razumjeli" kemiju morali smo pronaći i odgovarajući

pojednostavljeni prikaz. Zbog toga je u tijelo kemije uveden i utkan poseban jezik kemijskih simbola pomoću kojeg

opisujemo događaje. Taj jezik ima svoja specifična pravila - sebi svojstvenu gramatiku. Naučiti opisivati kemijske

događaje simboličkim jezikom, posebna je zadaća koja zahtijeva i posebne kognitivne sposobnosti. Upravo zato je

svladavanje jezika kemije upravo dobra vježba za mladi um.

To je razlog zašto tijekom nastave kemije treba veliku pažnju posvetiti pisanju ispravnih jednadžbi

kemijskih reakcija na temelju opažanja tijekom izvedenog pokusa. I to treba biti trajni nastavni cilj. Danas se to često

zanemaruje s obzirom na navodni veliki opseg nastavnih sadržaja. Uvedena je i Državna matura te je dodan samo još

jedna razlog u nizu da se "nema vremena baviti osnovnim stvarima". Međutim, pristupimo li ispravno ovom

nastavnom cilju i razvijemo li nastavnu strategiju koja će počivati na pokusima iznenada ćemo uštedjeti vrijeme. Bez

obzira na to koliko je planom i programom bilo predviđeno sati za vježbanje i učenje trajnih ciljeva. Na taj način

smanjit će se "pritisak", a povećati razumijevanje.Bitno je raspoznati i razlikovati glavne i sporedne nastavne, ali i

edukacijske ciljeve. S druge strane, ukoliko se nakon nekog vremena usmjerimo na složenije pokuse postići ćemo

puno više. Ali, trajne ciljeve treba vježbati na svakom nastavnom satu. Nikada ih se ne smije zanemariti. Na taj će

način učenicima postati navika ispravno bilježiti opažanja, pisati ispravne jednadžbe kemijskih reakcija i kritički

promatrati svaki pokus. Više je metoda kojima se može poslužiti ne bi li se zadovoljilo gramatička pravila kemijskog

simboličkog jezika. Pokazat ćemo to na nekoliko primjera jednostavnih pokusa i pri tome upozoriti na potrebna

predznanja i sposobnosti koje učenici moraju imati kako bi mogli uspješno učiti kemijski jezik

Kako poučavati znanstvenu metodu na jednostavnim pousima

Martina Palošika i Nenad Judaš

Kemijski odsjek, Prirodoslovno-matematički fakultet, Sveučilište u Zagrebu

martina.palosika@gmail.com iudas@chem.pmf.hr

Pokus koji smo odabrali za poučavanje znanstvene metode je poznati i izrazito jednostavni pokus u kojem svijeća

gori ispod čaše. Razloga za to je mnogo, no izdvojit ćemo sljedeća dva:

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a) pokus je toliko jednostavna daje teško reći da ga ne možemo izvesti,

b) iako se na prvo pogled čini i prejednostavnim ovaj je pokus u tumačenju izrazito zahtijevan i komleksan

Ovaj pokus se, kao i svaki drugi, može se raditi s bilo kojim uzrastom, a u nastavnikovoj je volji da odredi dubinu do

koje će s pojedinom grupom ići. U ovom radu namijenili smo ga učenicima trećeg razreda srednje škole, a nastavni

satovi bi bili organizirani u trajanju od 90 minuta.

U prvom dijelu sata učenici trebaju izvesti pokus i zabilježiti opažanja. Po potrebi mogu pokus ponoviti i više puta,

cilj je skupiti sve relevantne informacije i kasnije ih pokušati objasniti. Zatim ih treba ispitivati na takav način da

svojim odgovorima na postavljena pitanja, malo po malo, stignu to ispravnih odgovora - do ispravnog tumačenja

pokusa.

Da bi učenici mogli sudjelovati u ovakvom satu moraju već imati usvojena neka znanja, ali i razvijene određene

vještine i sposobnosti:

- navesti koliki je volumni udio kisika u zraku,

- definirati homogene i heterogene smjese,

- objasniti stoje to difuzija i potkrijepiti objašnjenje primjerom,

- objasniti stoje konvekcija i uslijed čega se ona javlja te objašnjenje potkrijepiti primjerom,

- objasniti utjecaj temperature na gustoću zraka,

- razlikovati otvorene i zatvorene sustave

- pisati jednadžbe kemijskih reakcija

- objasniti značenje jednadžbi kemijskih reakcija

- povezati odnos broja jedinki u plinovitoj fazi s njenim volumenom.

82

students' understanding of the intended concepts to be learned before, during, and after instruction. The results

revealed that ali the students vvere able to understand the concepts of electrochemistry regardless of the teaching

strategies. Hovvever, the groups vvith model-based approaches vvere able to develop significantly better quality of

mental models in learning the electrochemistry than the non-modeling approach groups. We also found that the

students had hybrid representations of different models before instruction, but fevver such cases vvere found after

instruction. Our findings indicated that using appropriate and multiple approaches for teaching abstract chemical

concepts should be encouraged for meaningful learning of electrochemistry for secondary students.

Conclusions and implications

Students tend to use their daily life experiences to explain hovv scientific theories function in a real vvorld. The

difficulty of learning science can be attributed to the nature of scientific concepts, vvhich are complex and

unobservable. The use of multimedia—dynamic, simulated, role play, or analogical representations that depict the

essence of the concepts in an attempt to match the scientific concepts vvith expressed or external models to help

learners develop concepts or ideas about phenomenon—could play a role in explaining phenomena. The gap betvveen

macroscopic experiences and microscopic representations needs to build a bridge to help students construct scientific

models for understanding the material vvorld in terms of atoms, molecules, and chemical bonding. We consider that

cultivating students' understanding of the definitions of a model per se is not a difficult task in science education.

Hovvever, the more challenging task is to educate them hovv to construct, validate, and reconstruct models that vvill

facilitate their understanding about science. Of course, teachers' pedagogical content knovvledge should be

developed professionally in order to improve their teaching in chemistry education.

Selected References

Chan. W. J. (2002). Investigating the effectiveness of dynamic analogy on learning chemical equilibrium—Eighth

graders' conceptual change on ontological nature of concepts and mental models. Unpublished master thesis, Taipei,

Taivvan.

Chiu, M. H. (2007). A National Survey of Students' Conceptions of Chemistry in Taivvan. International Journal of

Science Education, 29 (4), 421-452.

Chiu, M. H. & Chung, S. L. (2010). Development of students' mental models of electrochemistry using multiple

model-based approaches. Paper presented at NARST Annual International Conference, March 21-24, 2010,

Philadelphia, PA, USA.

Grosslight, L., Unger, C., & Jay, E. (1991). Understanding models and their use in science: Conceptions of middle

and high school students and experts. Journal of Research in Science Teaching, 38(9), 799-822.

Halloun, I. A. (2006). Modeling Theory in Science Education. Netherlands: Springer.

Johnstone, A. H. (1993). The development of chemistry teaching. Journal of Chemical Education, 70(9), 701-704.

Treagust, D. (1988). Development and use of diagnostic test to evaluate students' misconceptions in science.

International Journal of Science Education, 10(2), 159-169.

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Treagust, D. F. (1995). Diagnostic assessment of students' science knovvledge. In Glynn, S. M. & Duit, R. (Eds.),

Learning science in the schools: Research reformingpractice (pp. 327-346). Mahwah, NJ: Erlbaum.

Small Group Learning - On the Science \Vriting Heuristic

and Process Oriented Guided Inquiry

Thomas J. Greenbowe

Department of Chemistry, Iowa State University, Ames, Iowa, United States of America, tgreenbo@iastate.edu:

The Science Writing Heuristic (SWH) and Process Oriented Guided Inquiry (POGIL) are two effective guided

inquiry instructional techniques. Both are projects sponsored by the National Science Foundation aimed at

challenging high school and college students and instructors to do more than to follovv a procedure or to plug

numbers into a formula. Students vvork in small groups of three or four, under the supervision of a chemistry

instructor, to complete tutorials and laboratory experiments. Students are assigned roles of manager, recorder,

presenter, and reflector. Implementation of POGIL and or the SWH approaches have produced significant gains in

student test scores and have increased retention rates. An overvievv of POGIL and SWH will be presented, along

with specific examples of inquiry-based tutorials and experiments. Examples of student laboratory reports will be

presented, as well as student data on performance on quizzes and examinations, retention rates, and grade

distributions will be presented.

On the Croatian Small-group discovery-based learning strategy (SGDBLS)

Nenad Judaš

Faculty of Science, University of Zagreb, Croatia, e-mail: judas(g),chem.pmf.hr

Introduction

When teaching chemistry (science) we should have three general objectives: a) we should introduce our students

to the basic concepts of chemistry (content knovvledge); b) we should make it relevant to everyday life (context

knowledge) and c) we should make it attractive (appealing). During the past century a lot of thought and research in

science education was dedicated to objectives a) and b). Achievements accomplished with content presentation and

implementation of context-based chemistry into the curricula are in general satisfactory. Unfortunately, as can be

read from Thomson (1918) and Roberts (2002) reports, little has changed over the same period considering the

objective c). There are still no clear guidelines on how to create a climate vvhere young people would feel

enthusiastic about their experiences in school science and beyond. Creating such a climate \vould rely on:

13