TITLE: The Rusty Nails,

Teacher: Aimee Modic

Context:

Currently I am teaching a unit on chemical reactions including: balancing reactions, identifying the types of reactions and predicting products of selected types of reactions. Given the opportunity to do a formative assessment probe from one of the Keeley, et al volumes in lieu of a performance assessment, I perused them and found a probe that meshed very well with my topic.

Background:

We had been working on predicting products all week and had just finished some notes on predicting the products of double replacement reactions using the solubility rules; having studied decomposition and single replacement reactions earlier in the week. I asked if they would complete the probe for me (again, anonymously) and place it face down in the pile I created. I separated them into three stacks: those that chose A, the mass will increase; those that chose B, the mass will decrease; and those that chose C, the mass will remain the same. After reading through the students’ written responses and listening to the student interview responses there was one decision I was sure about: we need to do this activity

Task:

The students had been given the class period to work on any of three assignments that had upcoming due dates. I asked if they would complete the probe for me (again, anonymously) and place it face down in the pile I created.  This was the only day in a 7 class day period of time that I had enough time in the schedule to allow the students to complete the probe and with three items coming due most of the students seemed to take it seriously, but it would not surprise me if a few of them rushed through it to get to their work that would be graded. I chose three students to interview about the probe during our next available time

Results:

Of the students indicating the mass of the nails would increase due to the rusting process (5 out of 18, 27.7%) most indicated that the oxygen would somehow become bonded or added to the nails somehow … Two of the students (11.1%) said that the mass of the nails would decrease and the remainder of the class (61.1%) said that the mass would stay the same

The remainder, and largest portion of the class, had many variations on the theme of Law of Conservation of Mass

Closing the Loop:

I spoke to my class briefly about the results and indicated that pretty much everyone had something correct in their response, but that there were also a few misconceptions that needed to be cleared up. . I suggested that we set up the Rusty Nails activity when we return from vacation and actually make the measurements and the students indicated that it sounded like a good idea.

Reflection:

I have a very difficult time planning a way to fit them into my schedule. I tend to be a creature of habit and have certain activities that I feel are valuable for the students and like to include into my curriculum;  This probe in particular was an eye-opening experience for me on the misconceptions and seeming lack of preparation that several of the students are bringing to my classroom. I feel as though actually doing the lab will be of great benefit to my students. One of my colleagues and I have previously discussed the idea of using some pre-unit knowledge probes as a way of determining what our students know before we start so we can plan more effectively, and I saw several probes in Keeley’s book that piqued my interest;

Source:

Keeley, P,  Eberle, F. &Tugel, J. (2005). Uncovering Student Ideas in Science, Volume 1: 25 More Formative Assessment Probes. NSTA Press

Acknowledgement:

The author completed this assessment while a student at Montana State University