Exploring Electrolytes in the Lab with a PhET Inquiry

Have I mentioned that I’m obsessed with Ramsey Musallam?  In 2012, I had the opportunity to hear this passionate chemistry teacher speak at the ISTE Conference in San Diego.  I bought into his philosophy that student curiosity drives learning.  His teaching strategy made sense: Spark kids’ curiosity by letting them explore in the lab, then bring in lecture (often through video lessons) to push their engagement even further.  From a mentoring stand-point, I wish I could observe Musallam teach in his classroom, but since San Francisco is a long way from Chicago, I’ll settle for studying his teaching style through his videos.

I adapted a recent lab with Musallam’s “Lab First, Lecture Second” strategy in mind.  I typically implement a traditional Vernier Electrolyte Lab after my students learn how to name ionic compounds, covalent compounds, and acids.  In the past, I started this lab by lecturing about how ionic and covalent compounds behave differently when dissolved in water.  I emphasized the difference between the solutions ability to dissociate when dissolved in water.  By the time I explained the difference between strong and weak acids my students eyes had usually glazed over.  The lecture would be followed by a cook-book lab with Vernier probes and a bunch of post-lab questions.  Boring!

I took the old version of my lab and removed any pre-lab questions and unnecessary fluff.  A trimmed-down introduction provided limited background on the conductivity probe that would measure current passing through the solutions.  Students followed basic directions and measured the conductivity values of various solutions of ionic, covalent, and acidic compounds.  Rather than lecturing immediately after the data collection, I designed an inquiry segment using a fantastic PhET simulation from the University of Colorado, called Sugar and Salt Solutions.  The biggest disappointment I faced in this lesson dealt with the iPad’s inability to run this simulation.  A shout-out to the University of Colorado for working on Phet HTML5 Sims.  Unfortunately, this animation is not one of them.  Students in a 1:1 iPad classroom will need to use laptop
 computers for this inquiry activity or the teacher can guide the entire class through it using a projected computer screen.  The activity helped students visualize what was happening on a molecular level when different substances dissolved.  In all of my classes students shouted out “Wow, the NaCl just broke apart!” and “Why aren’t the ions together anymore?”  It was really cool to hear them coming up with intelligent conclusions on their own.  The inferences they made in teams

taught them more than my teacher-led lecture.  The simulation allowed them to change the solute to study the covalent behavior of sugar (they easily figured out that it stayed intact) and an ionic compound like CaCl2 (the 1:2 ion ratio was obvious to them).

Keeping NGSS SEP 4 in mind, Analyzing and Interpreting Data, I included data analysis in the inquiry activity.  SEP 4 states that students should “present data as evidence to support their conclusions.”  As students answered questions within the activity, they were asked to look back at their collected data to infer the relationship between the conductivity values of the solutions and the ability of certain particles to ionize as shown in the animations.  My gut feeling:  Students inferred the relationship between high conductivity values and dissociation more successfully than in my traditional Vernier lab with lecture coming first.  My post-lab discussion was shorter and more effective than in the past.  How do I know?  Their answers to the post-lab questions demonstrated richer understanding of the content.  Bottom-line, inquiry led to greater student learning.

Electrolyte Lab

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About Tanya Katovich

I am a proud mother to three beautiful girls and two dogs (one naughty, one nice). Currently serving as Vice-President on the NISE Board of Directors. Incredibly proud of winning the CICI Davidson Award in 2015. I love presenting, whether it's at NSTA conferences, workshops for teachers, ChemEd, or private consulting. I am National Board Certified in HS Chemistry,