The weather is a go-to topic of conversation, and for good reason—it affects everyone, everywhere, and is fairly easily divided into “good” and “bad”. Even smelly little kids like the students in your classroom know about weather, and can tell what a “good” temperature is, or what conditions they consider “bad”.
However, there is one element of daily weather forecasting that kids may have heard of, but have no idea what it really means: the barometer. This handy dandy Demo Science science demo will help you explain to your students what the barometer is and how it can be used to help predict the weather.
NOT 3.28 Feet of Baro
For this lil’ experiment, you’ll need but three things: a large bowl, a two liter bottle of soda (or other similarly sized pressure vessel), and water. Crack open the soda bottle, pour one out for the homies that ain’t with us no more, and, if you’re feeling generous, distribute the rest to your students in Dixie cups or whatever.
Now that they’re all hopped up on caffeine, gather all those smelly little kids around and ask them to sit still and quietly as you continue. Fill your bowl about halfway with water; fill the now-empty soda bottle to about three-quarters full. Place your hand, or, if you’ve got a really fat thumb, your thumb over the opening of the bottle and carefully turn it upside down.
Place the upended bottle in the bowl, with your hand (or thumb) on the very bottom of the bowl with the bottle still on top. Remove your hand (or thumb) quickly and carefully, and observe as hard as possible.
NOT A Cylindrical Length o’ Meter
If everything goes as it should, the water level inside your soda bottle should either rise or fall, depending on the ambient air conditions. This is caused by the changing pressure of the outside air on the water in the bowl, which in turn changes the water level in the bottle. With rising air pressure, water is forced into the bottle; falling air pressure will cause the water level to fall, as well. (These results are dependent on the pressure inside the bottle staying the same, which it should unless something went awry.)
Simple as it is, your soda bottle barometer can be used to predict future weather. High (or rising) pressure generally results in better, warmer weather, whilst low (or falling) pressure foretells colder temperatures and precipitation. Using far more sophisticated instruments, weather scientists can read and predict weather and climate patterns, and use this info to prepare citizens for weather events in the near future.