DAY 37 – Multivalent Naming

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Science 9 – Once again I managed to get a bit stuck into a rut with Chemistry in Science 9.  Lots of problems with these topics and lessons.  First of all, formulas and naming just isn’t that interesting. Students like to participate in discussions on atoms, electrons, etc, but the mechanics of naming compounds is pretty dry.

Nevertheless, I did my best to use some constructivist methodologies for these topics.  At some point the kids just have to be told some information, such that roman numerals are used to describe which ion charge a metal has.

I am continually surprised at how difficult students find the writing and naming of chemical formulas, I keep thinking that it’s something that I’m doing wrong and if I what I’m doing, the kids will be okay.  I debriefed on this topic with my students and it became clear that there are so many small things to “know” that the kids get confused.

I wonder if this type of topic is perhaps better served with some old school memorization quizzing and testing, prior to solidifying conceptual understandings.  In other words, nail the “knowing” first.  This argument is made often in maths, as well.

I actually had students figure out atom ratios for ionic compounds by drawing Bohr diagrams, prior to them being told any rules for writing formulas.  However, this kind of work/learning never seemed to transfer over to mastering the skill of writing formulas for compounds.

Truth be told, I think these topics are so out of context and abstract that they’re pretty much useless.  I would bet that a Chemistry 11 student could learn all of the naming rules in two classes, and that doing it at this grade level is truly not worth the effort.  This is also the last year this topic will be covered in science 9…

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Day 33 – Naming Compounds

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Science 9 – Despite the difficulties I have in getting students in grade 9 engaged, there are some days that are winners.  In the past, I would spend 15 minutes in front of the class and show them the rules for naming compounds and writing formulas for compounds. This year I asked the students to find the patterns themselves.  They see this as a challenge and worked really hard on the task.  When done, the students put their results on whiteboards and we went over the rules.

The Cognitive Load Theorists out there would likely poo-pooh the lesson. This was one of those “discovery” type lessons, albeit with a fairly generous entry point.  And in the end we summarized the rules on paper which could have been done at the very start.  However, CLT has nothing to say about motivation or engagement, and there is a big difference between having 30 kids mindlessly blasting through some worksheet/textbook type questions, compared to having 30 kids hunched over desks, participating in science discussions with their eyes wide open and focused on the task.

Day 42: Vitamin C Analysis

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Science 9 Students spent the class performing a lab where they use an indicator to determine relative amount of vitamin c in fruit drinks.  The lab was too complex for them to design all of their own procedures.  Instead, the lab is broken into two parts.  In Part A, students are given a dark blue iodine starch solution and a vitamin c tablet.  There job was to crush the tablet into a 100 mL water solution and then slowly dropwise add the solution to the iodine.  At some point the dark blue turns clear, indicating that the vitamin c has reacted with all of the iodine.

For Part B the students were to design a procedure for using the above calibration to determine the amount of vitamin c in different juices.  This proved to be quite difficult for some groups.  Several then started off with fruit juices and added the iodine solution to it dropwise.  They couldn’t see any colour changes, other than dilution, because should have been adding the juice to the iodine. I was a bit surprised at how many groups got this wrong. What didn’t surprise me is how almost all students immediately starting working on the lab prior to actually clarifying and writing a procedure.

The majority of students were able to use good reasoning and determined that apple juice, which took the fewest number of drops to clear the blue iodine colour, had the most vitamin c.