Todor et al (1988) consider that “the psychological process of formation of representations and notions about
nature run through, at individual scale, two stages”. In the first stage, named “the stage of notion’s elaboration”, the
school children become aware of objects, phenomena and processes by certain features/properties of them. Taking
into consideration the particularities of small school child’s thinking, the authors pointed out the necessity of using
in this stage of many modes of gaining knowledge, such as: the direct contact with objects and phenomena; the
indirect contact, aided by models, with objects and phenomena; the contact aided by word. With the aid of these
modalities of gaining knowledge, initially are formed to the school children the perceptions and representations of
concrete objects, and subsequently, based on them, the concepts. The authors emphasized that, for becoming able to
establish the general features/properties of studied objects or phenomena, as well as the essential relations between
them, the school children have to run through the following stages: