Study of plant material as potential acid-base indicators

U nastavi kemije često prevladava tradicionalni oblik rada kojim se gradivo samo usvoji što rezultira nagomilavanjem informacija. Ovakvim usvajanjem gradiva ostvaruje se niži nivo obrazovanja, ali ne i povezivanje naučenog gradiva sa svakodnevnim životom i njegova praktična primjena. Poznato je da vizualizacija nastave znatno olakšava smisleno i svrsishodno učenje, što se u učionici kemije postiže korištenjem pokusa. Obrada pojmova pH, kiselina, baza i indikator ponekad uključuje pokuse uz upotrebu sintetskih indikatora koji su često nedostupni školama. Međutim, biljni pigmenti mogu poslužiti kao kiselo–bazni indikatori jer ovisno o pH otopine mijenjaju boju od crvene, ljubičaste, plave, zelene do žute. Cilj rada bio je ispitati potencijal primjene odabranog biljnog materijala kao kiselo–baznog indikatora. U tu svrhu ispitano je jagodičasto i bobičasto voće, a korišten je sveži, suhi, smrznuti i prerađeni biljni materijal (džem, sok, vino). Odabrane su prerađevine s najvišim sadržajem voća. Rezultati istraživanja ukazuju na izuzetno veliki potencijal primjene biljnog materijala u nastavi kemije. Niska cijena biljnog materijala, dostupnost cijele godine, jednostavna priprema bez štetnih nusprodukata, mogućnost pripreme u malim količinama, jednostavno skladištenje i mogućnost pohrane na duži period prednosti su ispitanih alternativnih indikatora. Od ispitanog biljnog materijala, među vizualno najdojmljivijima istakli su se kupina, malina, ribiz, aronija i drijenak.In chemistry classroom the dominant teaching methods are traditional ones. Their result is accumulation of information which is a lower level of education with no application of learned lessons in everyday life. Visualization in science class allows meaningful and purposeful learning, with the help of experiments. Teaching of terms like pH, acid, base and indicator occasionally involves experiments, using synthetic indicators, which are often unavailable to many schools. However, plant pigments may be used as acid–base indicators as well, due to their different color depending on the solution pH value – red, purple, blue, green, yellow. The aim of this thesis was to evaluate potential of application of selected plant material as acid–base indicators. Studied plant material was soft fruit (berries) as fresh, dry, frozen fruit and fruit products (jam, juice, wine). Used products had the highest fruit concentration. Results indicate high potential of application of selected plant material in chemistry class. Low price, availability all year, simple preparation with no side products, preparation in small or big quantities, simple storage and possibility of longer storage are the advantages of studied alternative indicators. Of all studied plant material, especially visually impressive were blackberries, raspberries, currants, aronia and European cornel