Graphing the time vs temperature of ice water placed over a heat source as it changes phases is a pretty standard lab for 7th-grade science. Below is a PDF of a lab that may look familiar to you. Take a moment to read through it before we discuss how probeware can improve this lesson.
What is the goal of this lesson? I asked a number of teachers and got a variety of responses. All the teachers were hoping students would begin to learn about phase changes and temperature. A few teachers were concerned about student’s ability to read a thermometer.
NGSS goals for this lesson include:
|Disciplinary Core Ideas (DCI)||MS-PS1-4: Develop a model that predicts and describes changes in particle motion, temperature, and state of a pure substance when thermal energy is added or removed.|
|Science and Engineer Practices (SEP)||
|Cross-Cutting Concepts (CCC)||
Do you see any goal that includes “Reading a thermometer”? Nope! There’s a reason. For our middle school students who go to post-secondary education, the workforce is about 10 years away. In 10 years, how many jobs will there be that require someone to read an analog thermometer? Contrast that to how many jobs there will be that require someone to connect to a piece of equipment, download temperature data, and analyze it to determine the fault. The future is not reading the temperature, it’s knowing what to do with that data.
Using probeware changes the focus of the lab from reading thermometer values to plotting and analyzing the resultant data.
To further explain my point, let’s look at two different examples of student work. Both students measured and graphed temperature. One used an alcohol thermometer, the other used a Pasco Wireless Temperature Sensor.
With manual measurements, we get a graph that looks like this.
We’re in luck. This A student made a fairly clean graph, labeled the Y-axis, but substituted the X-axis label for the title of the graph. They also labeled “No more ice” at 1 minute, and “Boil” at minute 21.
The student using a temperature probe produced the following three graphs.
Graph one shows the entire data capture session.
Graph two shows the initial two and a half minutes. We can clearly see that ice persisted until about 72 seconds in, then the temperature began to rise suddenly.
Graph three shows the minutes leading up to boil. We can see clearly that at second 1,265 the temperature touched 99.9 degrees Celcius, but never exceeded that.