Home made Barometer

December 11 2010

Inspiration
More cub scout science this week with a home made barometer and some lessons about air pressure.

Materials
1 Milk bottle
1 Balloon - sliced open to form the flexible membrane over the bottle
1 Rubber band - to hold the membrane tight to the bottle, we used one of the jumbo punching balloons
1 coffee stir stick - to act as a needle
Elmer's glue - to attache the needle to the middle of the membrane
 a strip of paper to record the needle readings

Notes
This is an easy craftish event to do with the kids but the science and observation will take days and weeks to pay off so be patient.  The construction was easy enough and similar to making a makeshift kids drum with a balloon skin.  Be careful to use a long "needle" and glue it to the middle of the membrane so that the motion at the end of the needle will be clear.  We spent some time talking about air pressure and what would happen if the pressure changed outside the bottle, and the relationship to changing air pressure with certain inclement weather changes.  By looking up current pressure readings from weather.com we were even able to record values for our needle readings over the next few weeks which the kids still got excited about (and would even make their own predictions about the next day's weather based on their readings.

Here's the baseline.

The pressure dropped this day and it started raining soon after.