Chemistry at elementary schools: particles or also atoms – that's the question
At elementary school level, the description of substances and their changes is preferred by most guidelines of education. If the elementary school includes fifth and sixth graders like in Africa, it seems to be possible to introduce the idea of the Particle Model of Matter to reflect changes of states, dissolving and diffusing processes. As an example the solution of sugar in water can be represented by a mixture of spheres and crosses as in the figure below : one sphere shows a sugar particle, one cross shows one water particle. The only difficulty is the scientific language concerning the original sugar solution, the mental model in the cognitive structure, and the kind of concrete models – may be spheres and crosses or circles with different colors.