Physics & Physical Science Demos, Labs, & Projects for High School Teachers

Powers of Observation

Posted on: January 7, 2009

(This was submitted by Duane, a High School teacher in Georgia.  Thank you Duane.)

One fun “observation vs. conclusion / assumption” demo that I love came from Flinn Scientific’s “A Demo A Day” for Chemistry. I call it the “Potato Candle”.

Cut a cylindrical core (apple corers work well) from a potato – rinse it in lemon juice to preserve the near-white color of the cut potato – then cut a cross in one end. Insert an almond sliver (available at any grocer in the baking goods aisle) into the sliver. Your “candle” is now ready for the discussion / demo.

Inform your students that they are to practice their powers of observation, and make as many observations about what they are about to see in a limited time frame. Turning the lights down or out aids in their “mis-observations.”

Light the almond sliver with a match – it will catch readily, and burn for about 2 minutes – so don’t give them much longer than 60 seconds to make their observations. Blow out the almond before it burns out, turn on the lights, and start taking notes on the board as to the observations the students made of the “candle.”

At some point, particularly effective after someone makes the observation that the “candle” is made of wax, note that that’s an interesting observation, calmly bite the potato candle in half, chew and swallow. Your students will be aghast for a moment, wonder if you’re as crazy as that seems, and it leads into a lively discussion on the differences between observations, conclusions, and assumptions based on previous experiences.

Hope you like it!



1 Response to "Powers of Observation"

I love this- great for any class any time. Almost can’t wait for school to start up so I can try this.

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