Acid-Base Titrations or The Importance of Fast Failures and Quick Feedback

Titration

Friday was one of my favorite days of the year in my AP Chemistry class: the first titration of the year.  Let me quickly explain what I mean by a titration and why it relates to fast failures and quick feedback…  The goal of our lab period was for students to run numerous trials of an acid-base reaction in service of determining the exact concentration of a solution of a strong base (sodium hydroxide).  At the point when the amount of the base *EXACTLY* consumes the acid with which it is reacting, a previously added indicator (phenolphthalein) turns the solution from clear to a light, persistent pink color.  However, even one drop too much base and the solution will turn a deep, unrelenting pink/purple.  Pink signifies success, purple failure.

It was amazing to watch this group of highly talented students get into each trial.  They desperately wanted to achieve that light pink color.  However, the purple that so many of them saw indicated that their work did not measure up to a known, clear standard of excellence.  In fact, they “failed” the trial and needed another go at it, hopefully with a better result. My normally reserved group of students threw themselves into the lab, with each purple solution sending them rushing back to get more acid and start anew.  The quick feedback on their trials helped them understand that they were not quite where they wanted to be and that they needed to do it again.  And sometimes again and again…

Having worked as a chemist in a former life, I know that most chemists never complete a titration as part of their daily work.  So why teach it?  For the experience of helping students *SEE* how they can learn from feedback.  After the first failure (or second…or third), each student improved their technique and began to zero in on the light pink.  This experiment is also a wonderful reminder about how much students can learn (and how fast) when I provide them the feedback necessary to grow.  My students eagerly, willingly, and excitedly repeated this experiment in search of an acceptable pink result.  Light pink solutions were revered.  Some students even took photos of their solutions and sent them to friends.  That lab was a great learning experience for them.  And it was the opportunity to fail quickly and receive immediate feedback that made it so.

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2 thoughts on “Acid-Base Titrations or The Importance of Fast Failures and Quick Feedback

  1. Pingback: Acid-Base Titrations or The Importance of Fast Failures and Quick Feedback | Ms. Goodrich's Science Class Blog

  2. Pingback: Acid-Base Titrations or The Importance of Fast Failures and Quick Feedback | PRHS Chemistry Class Portfolios

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