Andras S. Szabo, Margit Izsak, Janos Bozi
When teaching physics and chemistry in schools, experiments are of primary importance. Students are satisfied if the investigated materials are food samples, well known to them. This paper deals with 10 simple experiments of chemical, physical and sensory type. The following foodstuffs were investigated: sugar, salt, egg, milk, butter, margarine, fat, lemon juice, apple juice, vinegar, baking powder, sodium bicarbonate.
We think that in the teaching of natural sciences, experiments are of primary importance. When chemical and physical experiments – with, of course, no sharp dividing line between these 2 subjects - comprise a dominant part of the education, students become more interested and the education process will be more successful, taking examples from practical life.
Today, modern scientific food investigations cover a rather complex field, since not only the basic requirement (food safety), but a lot of other parameters, like sensory quality, mass or volume, analytical composition, packaging, labelling, special – microbiological, toxicological, radiological – parameters are investigated, as well. Not going into details, let us stress that recently, instrumental analytical methods – techniques suitable for the determination of chemical composition – have been focusing dominantly on physical methods (e.g., NIR-NIT technique, dielectrometry, radioanalysis, viscosimetry) (1)2(3)(4)(5)(6)(7)(8)(9) – and even in microbiology, the rate of application of rapid, physical methods (e.g., conductometry) has been increasing.
Physical techniques have an important advantage in comparison with chemical procedures: they do not need chemicals, they are fast and non-destructive. These properties allow them to be applied in chemical process control – in the case of on-line and on-stream connection in industrial food processing (e.g., cheap filling products of the meat industry) – for regulation, based on composition measurements (chemometrics).
In the following sections, information is prpovided about 10 rather simple experiments, which can be carried out in normal labs of the schools. Before, during and after the experiments we have to mention the work and safety rules and the applicability and validity of the most important scientific laws. This means that the results of the studies should be interpreted on the basis of energy conservation, energy transformation and the principle of energy minimum(steady state). And it should also be pointed out that the pupils should not learn physics and chemistry literally (these subjects are not poems) but should strive to understand, endeavoring to interpret the findings correctly.
Although it was mentioned earlier that practically there are no boundaries between physics and chemistry – the expression „physical chemistry” is an excellent proof of this statement, having the following subfields: thermodynamics, reaction kinetics,electrochemistry, colloidics and rheology – of the 10 experiments, 5 belong mainly to physics, 4 to chemistry and 1 is a special one, belonging to sensory qualification.
This last one – because it is based on the application of the students’ own biosensors – is an experiment of the biological type, and it is necessary to mention that students participate with special enthusiasm in such types of measurements. Perhaps it would be interesting to study the maybe difference between the pupils and students, concerning the mean taste threshold value of perceptibility. It is known that the ability to recognize tastes depends not only on individual peculiarities, but age is a dominant factor, as well (10)(11)(12). read more ...