Precipitation reactions are ones in which at least one of the reactants is in the aqueous phase (i.e., dissolved in water), and a solid forms on the product side which was not present on the reactant side. If all the reactants are solid, then a solid product forming should not be called a precipitate. To be called a precipitate, an insoluble product must form from within solution, either from a solid and solute interacting, or from an interaction strictly between solutes.
The accepted views of science knowledge can change over time. Changes can result from new science observations, but can also be affected by social, political or religious convictions. To develop a deeper understanding, students need to investigate the context of the time in which science ideas were developed.
