Beyond Benign

Lead Teacher Blog

Cassandra Knutson

How to Go Green This Spring with Acid/Base Titrations

It’s never too late to include green chemistry in your curriculum! A common springtime topic in many chemistry classrooms is acid/base chemistry. This means that many chemistry teachers have a titration experiment on the horizon, which is a perfect opportunity for inclusion of green chemistry. Adding a titration following the Recycling Polylactic Acid experiment is an easy way to introduce or extend students’ knowledge of the Twelve Principles of Green Chemistry and polymers. During the Recycling Polylactic Acid experiment students degrade a polylactic acid (PLA) cup to its monomer, lactic acid, creating a green cleaner for the classroom. Following the degradation, students can titrate the lactic acid produced and find the experimental pKa to verify that it is lactic acid. Students can also quantify the concentration of the lactic acid sample through the titration. This experiment is versatile and accessible to various levels of students. The recycling portion of the experiment is available on our website or as a Flinn Scientific Kit and the titration portion of the experiment is available on our website. As a side note, Flinn Scientific offers a number of kits that address the principles of green chemistry.

The degradation of the PLA cup is a great platform for discussing green chemistry principle #7, use of renewable feedstocks, and principle #10, design for degradation. Using the degraded products as a green cleaner is a means of discussing principle #1, reducing waste. In addition, titration experiments meet many parts of the Next Generation Science Standards under High School Chemical Reactions.

In my experience, the degradation of PLA gave my students context around their titration, making it more relevant and engaging. My students enjoyed creating something that could be used in our classroom and seeing a recycling process in action. My students were aware of the enormous quantities of plastics that are accumulating in our environment and appreciated the opportunity to begin thinking about how scientists are addressing this concern and how they might be part of the solution as future scientists. These experiments were a great substitution for my traditional titrations, resulting in a much richer experience for my students with the additional exposure to the twelve principles of green chemistry and polymers.

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