In this work, we examine whether tenth-grade high school students (N = 197, age 1516) as well as first-year university chemistry students (N = 77, age 18-19) can make the connection between chemical reactions and chemical phenomena. We used nineteen physical and chemical phenomena, and asked the students at one stage to distinguish physical from chemical phenomena, and at another stage to state...

It is well known that when chemical reactions occur, the masses of the participating molecules are not conserved, whereas the masses of the nuclei of the chemical elements constituting these same molecules, are conserved. Within the context of non-equilibrium thermodynamics, the first fact is expressed by the differential balance equations, for the densities of the chemically reacting molecules...