Barometer

= Make a Barometer (MODIFIED) = = =


 * **Materials**
 * wide-mouthed glass jar or small coffee can
 * balloon (recommended) or plastic wrap
 * rubber band
 * scissors
 * drinking straw
 * cardboard strip
 * crazy glue recommended
 * ruler
 * small piece of modeling clay || [[image:http://www.ciese.org/curriculum/weatherproj2/images/baro1.jpg width="258" height="195"]] ||

> > >
 * Procedure**
 * Cut the narrow opening of the balloon off. (Double click on any of the images for a larger size image)
 * Cover the top of the jar with the balloon so that it is airtight and use the rubber band to hold it in place. IMPORTANT: the seal should be **airtight** (If you are using plastic wrap, it should make an airtight seal around the rim of the jar).
 * Place a small amount of glue in the middle of the balloon and carefully place the side of one end of the straw on the glue so that the other side extends over the edge of the jar. [[image:http://www.ciese.org/curriculum/weatherproj2/images/baro4_small.jpg width="101" height="78" link="http://www.ciese.org/curriculum/weatherproj2/images/baro4.jpg"]]
 * While the glue is drying, fold a piece of cardboard (see photo) so that it can stand on its own.
 * [[image:http://www.ciese.org/curriculum/weatherproj2/images/baro5_small.jpg link="http://www.ciese.org/curriculum/weatherproj2/images/baro5.jpg"]]
 * Optional:
 * Carefully, mark lines .5 cm apart and write "Low Pressure" at the bottom and "High Pressure" at the top. \
 * Once completed, place the barometer and the scale in the shoe-box sized cardboard box so that the end of the straw with the clay just reaches without touching the scale. Tape both the barometer and the scale into place so they cannot move
 * **Note:** Because we can not change the air pressure of our classroom for e DEMO; is good to place the jar on a hot plate for a couples of minutes and place a ruler (that already have measurement scale) next to the hot plate instead of the cardboard (for safety issues).

Describe to the best of your ability how this device actually measures air pressure. Include the following terms in your description: pressure, expansion, contraction, density.
 * How does it work?**

What can you do to improve the functioning of this device? Can you improve the accuracy? Precision? Can you make the device more stable or portable? You may select any materials we have here today or suggest alternative materials. Be clear in your description as to why these modifications will improve this device.
 * Engineering Experience: Ideas for Improving the Design**