At the end of modeling and practicing density I provided my chemistry classes with the following Lab Challenge (this idea took shape for me after seeing a Flinn email about how to make measurement interesting). I’m not sure this makes it interesting, but at least there is some motivation behind the measuring, not just doing it for nothing.
1) Pick any 10 items from the front tables and rank them in order of most dense to least dense.
2) Identify the chemical makeup (specific substance type) of the 10 items you measure.
Students spent the first class period making measurements on the different items. Some chose to use water displacement for volume, others used rulers for the regular shaped items. One of my big goals of this activity was to see how well students would remember all of the measurement rules and techniques we’ve already practices. (On their first mass vs. volume lab many failed to estimate a digit in their measurements) I also wanted students to show me they can organize a data table that contained ALL of their measurements (i.e. initial and final volumes) not just the actual volume they calculated. This is my Lab Goal #1 LAB.1 – I can recognize the precision of a measuring instrument, and record data in an appropriate, organized manner.
The second Lab Goal I assessed the students on was LAB.2 – I can design and/or follow an experimental procedure that tests a hypothesis, investigates a phenomenon, or solves a problem.
After the first class period most groups had their measurements made and densities calculated. Good start.
On day 2 I had the students finish their measurements and then begin searching online for densities of the various items. I did not provide any lists or other resources for them, just told them to start searching. As tech savvy as the students are when it comes to searching for real, relevant information they have a long way to go. Some were fine, but others were just lost. Part of my reason for this part of the challenge was to allow them to struggle a little bit in finding this information.
Finally on the 3rd day I gave the class the task to sort all of the items from the front table from largest to smallest density. Since each group only measured about half of the objects this took some class collaboration and problem solving as to how to handle this. This task proved to be an interesting study in class dynamics. Of my 3 classes each went about this in a different way. One class had each small group put a post-it note on each item and then were able to sort them that way. Another class had each small group put their sorted list of objects on the front whiteboard. That class proceed to find the overall largest, and if there were multiple measurements of the same item took the average. The final class had one representative from each group work together and started with the largest (kind of like class 2, but without writing everything on the front board).
As you can imagine there were definite challenges the group had. But as I talked about with each class was that this was a good simulation of what “real world science” looks like. Multiple small groups set out to solve the same problem. Those small groups then need to come together and collaborate and agree on something. They need to rely on each other and their data, and at the same time solve discrepancies that arrive between the sets of data.
Eventually the final product looked like this:
I would have liked to have their predictions as to what each substance was made out of on the board here as well, but we had a tough enough time just getting things lined up. Maybe we’ll discuss that the next day, but maybe I won’t worry about it. I talked with most individual groups as they were using the internet and searching densities anyways, so we might not need that large group time to discuss that.
Overall I really liked this challenge activity as a way to conclude Unit 1. This activity contained everything from experimental design, measurement, mass, volume, and density. If there is one thing I would change for next year it would be that on Day 2 I would have the class begin the process of organizing all of the materials right away since the groups have the densities. I would then have the students do the searching as homework or at the same time as the objects are being organized. I think that might be a more efficient use of time and would save us a class hour. But then again maybe not. Can you really rush good science?