Learning About Conductors Through a Demonstration Using Butter, Warm Water, and 5 Rods Made of Different Materials

The graph above is interactive.  Hover over it and notice the five circles that appear.
Hover over each circle to see when on the graph each butter pat slid down the rod.
Thanks to thinglink.com!

Today, our class learned about conductors (insulators are coming on Wednesday) as they relate to heat transfer.  We predicted that the type of material an object is made of determines its rate of heat transfer, so naturally we needed to test out various materials!

We used five rods made of different materials: brass, copper, aluminum, plastic, and wood.  On each rod, we placed a frozen pat of butter at one end (see the picture for a better idea).  We placed each rod into a glass jar filled with hot water, sitting on a hot plate which allowed the water to continually heat up.

I placed a temperature probe into the water to track the temperature during the experiment.  The results of that are in the data chart on the left (and the graph above).  The top of the glass jar was sealed with plastic wrap to contain the heat, and all rods and probes were poked through the plastic wrap.

This experiment was actually done as an demonstration.  We discussed the procedure and materials of our experiment, and then set it up and conducted it.  We observed the butter melting and sliding down each rod, and recorded the data in our science journals.  Students discovered that the metals seemed to conduct heat faster or better than the plastic or wood did.  We discussed how brass and copper are good conductors, but how aluminum is generally considered a poor conductor.  This was an anomaly in our results.  Aluminum should have slid later in the experiment.  We discussed how experiments are far from perfect and that results are often incorrect or inconclusive due to errors in the set-up or other variables.  (For instance, one student kept bumping the table during the experiment and we had to ask him to move!!!)

This was a good experiment for understanding what a conductor is.  The main reason it was so valuable was because of the discussion we were able to have during and after the experiment since we used "conductor" so often.  We discussed what properties might have made a material a "good conductor" and what would make it a "bad conductor."  We avoided the term "insulator" because that comes later.  Although we don't know the exact scientific reason why a good conductor is a good conductor, we did analyze the materials, make logical conclusions, and use prior knowledge in our conversation.  Lots of great thinking and learning going on in this lesson!  :)

Above: Ryan and Erik watching butter melt - how exciting!  :)

To the right: Our butter pats on five rods made of different materials (brass, copper, aluminum, plastic, and wood).