on the topic of Science Teaching
Talking about thermometers is never an easy thing.
Neither is mentioning the idea of thermal expansion. But, through sections 1.3 and 1.4, my students were able to grasp both concepts quite easily, even if some occasionally forget to remove the case around the thermometer before measuring!
In section 1.3, the focus begins on getting students used to using the thermometer and understand how it works. I really liked this for two reasons. The first was that they got their hands on actual lab equipment and learned a skill that even high school students sometimes perform incorrectly. Second was that they didn’t just learn to read the measurements given; they began to understand how chemistry played a role in the liquid rising and falling.
Though we don’t get into conduction until chapter 2, the idea that the molecules increase in energy and motion, collide more, and have more spacing between the molecules (thus increasing the volume of the object) is a great one. The students easily can relate to this, having witnessed doors stuck in their frames during the summer, and having heard of the trick of running a jar under hot water to loosen the lid.
I believe that making those real-world connections really helps the idea stick. However, there is one point worth stressing over and over again:
THE SPACING IS INCREASING, NOT THE SIZE OF THE MOLECULES.
It seems that every year there are students who think that the size of the molecules is increasing, and not the space between molecules. Some even carry this misconception into section 1.4, where we discuss the molecular structure of solids, and through the ball and ring demonstrate thermal expansion of solids. 1.4 goes pretty quickly for me, so I use the rest of the time to hammer what may be the greatest acronym ever:
The EMCS (pronounced E-M-Cees)
The EMCS stand for Energy, Motion, Colliding, and Spacing, and really help when explaining how molecules act when heated (increase in energy, motion, colliding, and spacing) or cooled (decrease in energy, motion, colliding, and spacing). My colleague showed this to me when I first started teaching 7th grade chemistry, and I have used it ever since. It helps to dispel the misconception, and gives us a fun way to remember the concepts.
We also use the EMCS in a song. What song? For that, you’ll have to wait until the next posting