Why Is a Drinking Bird Like a Dog on a Hot Day?


Ted Beyer, Educational Innovations, Inc.By:  Ted Beyer

Summertime—sun and fun!  For most of us (in the northern hemisphere at least) that means hot weather.  Heat does interesting things to the world around us, and to us as well.  On a hot day you tend to perspire.  Your body does this for a good reason:  as the moisture evaporates, it cools your skin, and thus helps to regulate your body temperature.

In contrast, dogs don’t perspire—they don’t have sweat glands!  So on a hot day you will see dogs panting—lots of rapid, shallow breaths with their tongues looking bigger than usual hanging out of their mouths.  That’s the doggie way of cooling off.  They are moving air over a wet surface—again using evaporation to lower their body temperature.
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The Amazing Drinking Bird


Tami O'Connorby Tami O’Connor

Invented in 1945 by Miles Sullivan, the “drinking bird” has been a favorite of science teachers in every classroom from kindergarten through college. This amazing device is made of two glass bulbs (one representing the head and the other representing the body) joined by a glass tube (representing the neck).  Between the two bulbs, attached to the glass tube, is a metal fulcrum upon which the bird pivots.  The air has been removed from this closed device, and the bottom ball is filled with a colored liquid that has a high vapor pressure (methylene chloride). The rest of the bird’s body and head is filled with the vapor form of methylene chloride.

The demonstration is set up such that a glass, filled to the top with water, is placed in front of the drinking bird. The glass Drinking Birdshould be the same height as the pivot point of the bird. The bird’s head should be moistened and then the bird should be given a gentle push to begin it oscillating along the pivot point.  Eventually, the bird appears to drink repeatedly, on its own.  So, how does that happen?? Read the rest of this entry »