Common Sense Chemistry

This week, my students began their participation in the Open Notebook Science Solubility Challenge. Determining the solubility of an organic compound in a solvent is not the most demanding experimental goal but it does present a significant challenge for students if they are designing their own experiment. So far this experiment/experience has taught me the value of having students think through and trouble-shoot a relatively simple experimental protocol. I set up the experiment so that students would pick their own solute from the stockroom spreadsheet and their solvent from a list of common solvents. Even at this point some wet chemistry wisdom becomes important. How would you propose to separate a room-temperature liquid solute from a saturated solution? What solvent characteristics are desirable if we are going to use a boiling water bath to evaporate the solvent? Is it likely that a polyol sugar derivative will dissolve in hexane? As we think through the procedure other challenges arise. What is the optimal mixing vessel given the volume requirements? What is the best way to mix the solution? How will you know when the solution is saturated? Measurements are critical and ultimately rely on solid math skills. What measurements are necessary to provide information for determining the solubility data in Molarity, Molality, g solute/100g solution, and so on…? nl_centrifugeHow will the calculations be done? How do we know if our numbers are “good?” This experiment is a good example of an experiment that provides not only answers, but raises vital questions that are essential to the scientific process. What I am hoping for is that my students will see themselves as part of a larger scientific community where asking and answering these questions is important, not just to get a good grade but to advance the scientific endeavor.

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