This diploma thesis discusses the three levels of chemical concept; the Johnstone's triangle of three learning levels of chemistry; the interdependence of the three levels of science concepts model; the teaching and learning chemistry model; the visualization tools; the Paivio’s dual coding model; the results of the researches based on understanding of selected chemical concepts (element, compound, pure substance, mixture, state of matter, physical change and chemical reaction), submicroscopic representations, chemical equations and the methods of teaching of all the selected chemical concepts except pure substances on a submicroscopic level.
The main purpose of the diploma thesis is to find out whether there are any problems with ninth grade primary school students’ understanding of the selected chemical concepts on a submicroscopic level, the changing states of matter on a macroscopic level and the chemical reaction on a symbolic level.
The results of the research have shown that the students in ninth grade have the most problems with decoding diagrams representing the arrangement of particles in a gaseous state and with forming the correct chemical equation on the basis of a submicroscopic representation. Other researches also showed that students have problems with understanding of symbolic forms.
Approximately two-thirds of the students did not differentiate between the submicroscopic representations of water in liquid and solid state or did not identify a mixture of elements, a mixture of two gases/a mixture of an element and a compound from diagrams of particle arrangements.
More than a half of the students could not identify the changing states of matter (water) on a macroscopic level (melting and evaporation) or did not recognize the product (gas) and the reactants in a chemical reaction (2 elements) based on particulate representation. Less than a half of the students had difficulties with recognizing the physical change and its properties; the liquid state of matter; the compound; the mixture of gases from submicroscopic representations and with differentiating between the chemical concepts element and compound.
Ninth grade students were very successful at defining submicroscopic representation of an element in a solid state; at identifying the process of freezing on a macroscopic level and at recognising a mixture and a pure substance on a particle level. They were also successful in identifying the process of condensation on macroscopic level and sublimation on submicroscopic level.
The research shows that the students have difficulties with understanding some of the selected chemical concepts on a submicroscopic level as well as the changing states of matter of water on a macroscopic level and a chemical reaction on a symbolic level.
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