The use of probabilistic concepts is suggested as a way to explore the main differences in the behaviours of solids, liquids and gases with high school pupils. The idea of correlation is introduced with reference to macroscopic systems and then applied to describe the link between particles in solids, liquids and gases: analysis of the graphs of the radial distribution function allows pupils to construct a representation of how the three states of matter are differentiated by the nature of their order and to explain phenomenological observations. Results of a first trial of the proposal with pupils attending the final year of high school are presented.