Tuesday, December 9, 2014

Predicting Products, Part 2

Now that the students have learned how to predict products, it's time to put the skills to the test in the lab.  Since this skill is about looking at the ingredients and predicting how they will interact, this is a great time for a Choose Your Own Adventure lab, a lab where the students design their own procedures.

We start with this premise:  Remember those logic puzzles that you did the day before vacation in elementary school that started with something like "Seven ladies live in 7 different colored houses with 7 different pets?"  This is going to be the lab version of that.  There are 5 beakers, labeled A, B, C, D, and E with 5 solutions that are AgNO3, BaCl2, CuCl2, K2CO3, and NaOH.  Figure out which solution is in which beaker.  The only things you can use to solve the puzzle are these 5 solutions.

With that, they move into the lab and start making a plan.  Eventually, they get the solutions and start mixing them together.  I have suggested they use a spot plate for this, but I haven't made many other suggestions.  They keep track of their data in different ways - some make tables, some make lists.

There is this great quiet buzz in the lab as they work; the conversations are awesome.  They have to know how to predict the products of a double displacement reaction because they have to predict the products of reactions between every combination of the above compoundsThey have to know how to read and interpret a solubility table because they have to predict the identity of the precipitates.  They work together.  They explain their reasoning to each other.  For some, their understanding of this reaction type deepens.  Others realize that they don't understand the work which ups the ante for them to dig in.

I have told them that their grades on their lab reports are entirely independent of whether or not they identify the solutions correctly.  But they don't care.  They want to be right because they want to be right, not because they are getting a grade.  They want to solve the puzzle.  When kids finish quickly, they ask if they are right.  Many leave class saying things like, "I really liked that lab" or, even better, "That lab was fun."  It doesn't get any better than this. 

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