Testing Our Thermal Loss Procedures

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Objective

Using a typical calorimetry experiment, students will test their strategies from the previous class for estimating energy lost to the surroundings.

Big Idea

Scientists test their ideas to see how well they adhere to real world situations.

Warmup

20 minutes

Previously, I had asked my students to consider ways that thermal losses could be observed and measured. Students had quickly designed procedures to accomplish this. Today, we take some time to test those procedures and, in the process, make our thermal model that much more sophisticated. 

In order to both provide a "bell-ringer" and to suggest a method for testing energy losses, I provide the water mixing warmup problem.

My goal is to get students to realize the importance of being able to both predict and measure the equilibrium temperature for a system where all of the inputs are well-known or can be accurately measured.  The difference between the expected and actual temperatures can be converted into energy that left the water mixture.

One way of estimating losses is suggested to the students who may choose to use this method. Alternatively, they can use the method they devised in the previous lesson.

Estimating Energy Losses - Implementing Procedures

40 minutes

Having spent the beginning of class pondering how to estimate thermal losses, students are primed to implement their strategies for estimating energy losses in a calorimetry experiment.

In order to foster a sense of reflection (on process) and to promote a sense of "rapid prototyping," I tell students to create a quick experiment, then consider the results before adjusting their approach. I also tell them that I'll be interviewing them to report out on round one results, along with ideas they have for enhancement.

Students then proceed to gather the specific material needed for their distinct implementation. I circulate to prompt conversations about their process and to keep teams from getting too locked in to "perfection;" it is far more important to do something relatively quickly and make observations than it is to over-plan and only get one data trial completed (or none!). 

Here's a sample interview where students were successful at quantifying the energy loss:


 

Reporting Conclusions

20 minutes

After testing procedures, students are expected to share their results. In the final segment of class, student groups report out on their results, with each team taking a few minutes to stand in front of their peers to share results.  The expectation is that groups should quickly recap their procedure, show a sample result, then summarize their conclusion based on multiple trials.  When students are not presenting, they are acting as peers in a peer review session.

The rationale for this segment is that when teams know they must confront an audience of peers, they are more likely to truly reflect on their own work.  My role during these presentations is to help keep the discourse civil - it is imperative that all students feel safe during the critiques.

The assessment of this is highly formative.  My true goal is to create an experience that is authentic and creates a general feel of a peer review session in a working laboratory. This activity does more to set a tone - that students will be active and will take on roles that real scientists take - than it does to reveal deep insight into the content of thermodynamics and thermal losses.