The Extraction and Isolation of Saltpeter from Nitered Soil. A Curriculum Alignment Project for a First-Year High School Chemistry Course

One of the problems with many published experiments for the high school level is that they appear as isolated entities in the eyes of the students, having a duration of only one or two class periods and usually connecting to just one or two major concepts in the curriculum. This article describes an experiment that can move beyond this limited function and instead can act as an overarching project, tying together several chemistry concepts. Further, the experiment engages students in synthesizing several different laboratory techniques as they are required to extract, separate, and purify calcium nitrate (from an enriched soil sample) and then convert it into potassium nitrate, which is isolated. As an extension of the main work, students are asked to combine the potassium nitrate generated with the other two ingredients of black powder which can then either be tested for proper burn characteristics or used in a followup experiment. During the course of this multi-week investigation, students will be asked to apply concepts related to separation techniques, intermolecular forces, ionic bonding, qualitative analysis, and solution and oxidation–reduction chemistry. It is a process that will ideally leave them with a sense of the cohesive, interconnected nature of real chemistry.