Saturday, August 30, 2014

Mixed Experience with Net Ionic Equations

Generally, my thinking is that iPads will reinforce a skill but in a much deeper way than just practicing the skill on a homework assignment.  This did not turn out to be the case when I had students create screencasts of "net ionic equations."

I think that writing a net ionic equation really synthesizes many different skills and concepts learned in a chemistry class.  The students have to demonstrate that they know how to write symbols and formulas, balance equations, predict products, know the solubility rules, distinguish between strong and weak acids.  In other words net ionic equations are one of those things that "ties it all together."  So what a perfect type of skill to demonstrate on a screencast.  I assigned my students each a different equation.  They had to write the "molecular", "total ionic" and "net ionic" equations.  As they wrote they had to audibly explain what they were writing.  This is no different from other screencast assignments.  My thinking was that the assignment would make them learn the skill so deeply that they would all "ace" the exam.  This did not happen at all.  Here is a typical problem:

"Hydrochloric acid is added to sodium fluoride."  Here is a screencast of a student performing this skill.

This is the type of problem that gives students fits because you are given a strong acid HCl and it produces a weak acid HF.  In the total ionic equation H + (aq) and Cl- (aq) are written separately because HCl completely ionizes in aqueous solution.  Conversely HF(aq) is written in its molecular form because it mostly stays unionized as molecules.  Students have a difficult time with this.

Here is another example screencast of net ionic equations.  In that example a precipitate is formed.


Students tended to explain the concepts and write them out correctly in their screencast. But when it came to the exam a very large number of students did not receive a passing grade.  In fact it was well over half that did not pass.  I was very surprised.  During a subsequent laboratory time I called many students up individually and asked them why this happened.  I showed them their screencast that was done correctly and then I showed them their exam with a similar problem and it was done incorrectly.  In several cases on the screencast the students correctly showed the weak acid written as a molecule and even noted clearly that it was a weak acid but then on the exam they wrote the acid in ionic form.  Many shook their heads. Many were unable to explain why this happened but almost all quickly and clearly understood their mistake.  It is very hard for me to come up with a clear explanation of this.  I will say it again. I totally expected that the screencast would have driven home the concept.

I have to come up with something so here it is.  This was a six week class in the summer.  This particular summer we moved the concept of net ionic equations to an earlier time in the curriculum calendar.  I think that the students just did not have enough time to learn these concepts deeply enough. I think they got it well enough to explain in a screencast (They had about 2 hours to do the screencast) but not well enough for a pressure filled exam.  This was a good lesson for me to learn.  iPads are not the be all end all.  They are just a very good tool that will help, but they are not magic.

Good News in the End!

I did something I have never done before.  The test results were so bad, among the worst I had seen in college, that I actually gave a make-up test.  The students knew the gravity of the situation and also knew how much I was bending over backward to help them succeed.  They did better.

The students got a third chance on the final exam.  Net ionic equations show up on the final.  The difficulty of the problems is the same.  This time all but one student passed the part of the final exam which includes net ionic equations.  My thinking is that for them to learn it deep enough for a high stakes, high pressure exam, they need much time and multiple modes of reinforcement.  Do I plan to use iPads again this new semester in my Elementary Chemistry class to practice net ionic equations?  Absolutely!  I am just not going to expect the iPads to do something impossible.

2 comments:

  1. When do you first introduce the iPads? Because I introduced them during the first week of class and the results were quite disastrous......

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  2. Linda,

    I am sorry it has taken so long to get back to you. I do not introduce iPads right off the bat. I usually bring them out a month or more into the term (semester). For me iPads are just a tool. When I grew up in school I took woodworking class. I remember we learned to use the tools progressively. So we started out on the simplest and safest saw, the scroll saw. When the teacher felt we could be trusted we went up to the band saw and then, well you get the point. So it goes with iPads. I don't bring them out right away because I want to get to know my students first and establish my expectations for them. I want them to get to know me as well. When there is a bond of mutual trust I can get out the iPads. Using iPads the students will have a lot of freedom to go outside and create their screencasts. Students could probably figure out a way to walk away with an iPad, but they don't because I think there is that mutual trust and relationship. Also they know that I expect quality work from them. So when they use the iPads those high expectations are know and established. That is why I wait until several weeks into a semester. Now at my sons's Junior High School they gave the students iPads before school even started. But as a parent I had to sign a long contract that I discussed with my child. There was a big school wide meeting on the expectations. All of the teachers reiterated those expectations. So I think the students got the message. So the bottom line is clear, established, high expectations and trust. Thanks for your question.

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