Thursday, July 12, 2012

#ModChem Day 4

Modeler's Log, Day 4 --

This modeling chemistry business keeps getting better and better! Today, the focus moved us more into the motion of particles and factors associated with their motion.

We read and discussed an article by Bruce Alberts called Restoring Science to Science Education, where Alberts talks from a scientist's perspective on how science education (in the lecture-demo based traditional approach) is a caricature of real science. We discussed Alberts notion that poor science instruction turns students away from science careers and does not teach them understanding. He blames the standards movement, which gave rise to the high-stakes standardized tests, that exerts a subliminal force on education to teach to the test. He proposed revamping and simplifying the educational standards to four main strands for science education; similarly, he outlined a four-point plan for improving science education at the national level.

We identified ways that we, as classroom teachers, could take part in Albert's plan, or parts of it. Many of us agreed with points in Albert's article, as it is a similar concern that we in the modeling workshop have about traditional science education--it looks very little like doing science--we are here training to be better science educators in order to provide a more authentic science experience for our students. With the current move toward delineating the Next Generation Science Standards, we could all relate to what Albert was saying. One important final point that came up was related to Albert's position as a biologist talking about education. His opinion in this article is fairly well known and respected; however, had he been an educator, would his ideas have been taken as seriously by readers?

It is essential that modeling workshops have a scholarly literature review component. Without the discussion of the ideas and background that motivate a move toward a different approach to teaching science, we are not fully embracing the modeling instruction for all that it is. To change for the mere sake of change, or to "try out modeling" simply because it "sounds" good is not enough--we need to have the full picture and a better understanding of what it's all about. This is why I find it so important to reflect on the articles and take their discussion into consideration in my recap of the workshop day.

After the productive and constructive discussion of the article, it was on to labs! We picked things up with the difference in particle motion we observed with the red and blue colored food dye in different temperatures of water at the end of day 3. We surmised that warmer particles must move faster based on the evidence we saw. This was the springboard point for what we did today.

Interesting side note, I had a thoughtful exchange with Brian Vancil (@bvancil) on Twitter yesterday about this very demonstration. He took note of the video I posted depicting the food coloring in water and presented some additional factors that could influence particle motion. The exchange was so moving that he recreated the experiment under different conditions to try and isolate the system as best he could to show the effect of temperature (without influence of other factors) on motion of particles. Just goes to show how useful of a tool Twitter can actually be for teachers to think through ideas for lessons together. Thanks Brian!!

Ok, back to the action of the day.

We examined the nature of the motion of particles in solids, liquids, and gases. This extended into demonstrations of changes of state and considerations of the energy transfer involved in those processes. Expansion and contraction were ideas introduced in this discussion, and those terms became helpful in understanding how thermometers work. Observing what happened in this demonstration of ethanol (green) and water (yellow) being heated led us to get a sense of how expansion had to do with temperature.

A formal definition for pressure was established, also through discussion demonstration, and we came to use "pressure" as a means of explaining what was happening in the situation of drinking through a straw.

 Our instructor "crushed" a soda for us and we discussed changes in the pressure, volume, and temperature of the can. After observing this can crushing phenomenon, which rarely fails to impress, we were prompted to consider factors that might affect gas pressure. In a classic inquiry-style experiment, our instructor led us to determine what factors we thought might affect gas pressure, determine which we were able to directly measure given our equipment, and to then decide which measurable factors we could compare to pressure. Our group narrowed it down to volume, temperature, & amount of gas.

It's important to point out that no introduction of the term molecule or atom has been made yet, and the phrase "amount of gas," which is colloquial for moles (n,) is intuitive enough to the untrained student that they can use it without having to know anything about moles.

After determining what we were going to compare, we designed three experiments that we carried out using Vernier lab sensors and high-tech equipment. We compared pressure to volume by pulling a syringe to varying volumes while attached to a pressure sensor. The handheld Vernier LabQuest recorded our data for us and I then plotted it in Graphical Analysis for iPad. Since all the relationships we have seen up to this point have been linear, we first tried a linear fit. It didn't look so good, so we tried other fits until proportional. Though we were encountering this for the first time in class during this lab, it was pretty clear to understand what it meant in the context of the lab.

The other two labs (Pressure v. Temperature and Pressure v. Amount of Gas) also took place in similar fashion using similar equipment. We graphed our data and looked for relationships. Through lab debrief, we arrived at three different relationships, all showing factors that affect pressure of a gas. The data collection for these labs took a while. The debrief was so critical to our model building that it also took a while. The day ended with lab debrief. We learned the difference between a direct (y=mx+b) relationship and a directly proportional (y=mx) one. Then, the most interesting thing happened after we learned that the difference between these relationship types while looking at the graph of Pressure v. Temperature. We reasoned that this relationship had to have a y-intercept value, because we all know you can have particle motion at zero degrees (e.g., very cold temperatures.)

So, we speculated about what the trend would be if we were able to get the temperature colder, and colder...and colder. We used the mathematical model for the graph of Pressure v. Temperature to determine how far back the temperature would go before there was no more gas pressure, e.g., when  the molecules would stop moving, colliding, and exerting pressure. Guess what! It turned out in our data that the Celsius temperature at which we predicted particles would stop moving was about -272 degrees! Our teacher suggested we take that difference into account and re-plot, what she called, the absolute temperature and pressure. When we did, the relationship came out to be directly proportional. I had an epiphany at this point! Though I was already sold on modeling instruction, this really impressed me.

My epiphany was that we were giving students authentic experience and empirical evidence to deduce absolute zero temperature and arrive at a physical meaning of it. This is important for two reasons to me: 1) it is imperative that students have a context with which they experience the learning and construct it on their own if they are to understand it fully, and 2) I always knew what absolute zero was, I even know the graphical explanation of it--I remember learning it from my chemistry teaching telling me in high school and I always felt that I "understood" it; HOWEVER, today when we did that lab and I saw the extrapolation to absolute zero based on our lab data...I realized that I in fact had no genuine sense for what it meant prior to today. I was able to bypass my own retrograde amnesia and have an authentic learning experience in the modeling workshop with the content just as the students would. This fascinated me and reaffirmed my belief in the success of modeling instruction.

Any teacher could show their students the graphs of the relationships to gas pressure, and any teacher could tell their students about absolute zero--it's a term students have heard and do use; however, providing a context in which the students can uncover this information for themselves in the scheme of their own model for the particles of matter and arrive at an understanding of the relationships and the significance of absolute zero (and eventually the Kelvin temperature scale)...priceless!


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