I recently decided I needed to step up my game in the classroom. In fact, I decided I needed to change the setting altogether. So, I donned my Slytherin robes, (Yes, I’m Slytherin!) brought out my Elder wand and conducted a lesson on Potions. Yes, Potions. As a chemistry teacher, I’ve always wanted to take my lesson planning to the next level and create a curriculum entirely based on Harry Potter. (J. K. Rowling: If you ever read this, my offer still stands on a Co-Op!!) How fun would it be to officially rename my course Potions and tailor fit every unit to the muggle world? Well, we all must start somewhere, so I started with one lab. And holy MOLE-ly, was it a success.
If you caught that pun, then you know that this lab was centered on the mole concept. For those of you not current on your chemistry I’ll review the basics. The mole, in short, is a quantity, similar to how a dozen is a quantity. If you need a quick refresher, you can brush up on your skills here. Part of the mole unit includes using the periodic table to recognize molar masses of elements, how to calculate molar quantities, and understanding how to create molar solutions (I mean POTIONS!!!).
AND this is where potions come into the picture. I’ve always taught molarity by having students create their own molar solutions. This is a laboratory activity that I highly recommend to all chemistry teachers because students cannot learn this skill through word problems alone. Students need practical engagement with volumetric flasks, the molarity equation, and understanding how to use the periodic table. Every year that I do the molarity lab, I see the misconceptions. Students are good at putting numbers into equations, but put those kids in a lab, and they cease up like butter on ice. SO, without further ado, here is my rendition of Harry Potter’s Potions lab as an engaging way to teach molarity.
Objective: Students will use their knowledge of the molarity equation to create an assigned molar solution of Copper (II) Sulfate Pentahydrate. (Note: Copper (II) Chloride is an acceptable substitute for Copper (II) Sulfate Pentahydrate.)
Overview: Each lab group will be tasked with making an assigned molar solution of Copper (II) sulfate Pentahydrate. After each group has created their solution, they will test their accuracy by graphical analysis of known molar solutions (Beer’s Law) through the use of a colorimeter.
Materials: Volumetric Flasks of various sizes between 25 mL and 100mL (quantity dependent on class size), Solid CuS04-5H20, Scoopulas, DI water, Colorimeter (I use Vernier), LoggerPro software.
Prior Knowledge: Students should be familiar with the molarity equation and should have an understanding of dimensional analysis. (Beer’s Law is not required knowledge for this lab, however, for Advanced Chemistry courses, this would be an appropriate extension.)
- Instruct students that they are tasked with creating their own potion!
- Each “Potion” must have the assigned molarity. (I give these to students on a card)
- Students go to their lab stations (each with the materials and assigned volumetric flask) and must create their potion based on their understandings of the molarity equation.
- When all the students have created their potions, I explain Beer’s Law and show them (using my computer) how to create a line of best fit with known concentrations of CuS04-5H20. (If you are unfamiliar with Beer’s Law, here is a demonstration from the Vernier Website.)
- Once our line of best fit is created, students test their “potions” to see if their molarity has the predicted absorbance.
- Get ready for excitement! Students love to see how close they are to the predicted absorbance. We were lucky enough to see students obtain PERFECT absorbance values for their potions!
I give homework passes when students win competitions. You can tailor the class to best fit your needs. Please feel free to contact me with any of your questions or if you need any assistance. Below is the link to the student handout. Feel free to use and modify for your classroom!