Here we construct an aneroid (without fluid) barometer from a collection of simple materials that you can find at the supermarket and local hardware store. Your barometer can be used to track changes in air pressure with weather or it can be used as an altimeter. It is also affected by temperature, so it will provide good practice in the experimental technique of "holding independent variables constant". While we've posted this exercise on the L. M. Nixon Noon Science website, the calibration and analysis is probably at the extreme limits of the skill level of the typical 5th grader, even for our recently-simplified version.  But let me know if I'm wrong! (revision 4-29-06) Materials 1. Large balloon, 11" or larger.  Get a good quality balloon; the cheap ones slowly leak. 2. Rigid plastic or glass cup.  If you select plastic, spend a little extra and get very heavy-grade cups. 3. Rubber bands (#30 size seems good, they are about 2" long.  They'll need to fit tightly around whatever cup you select.). 4. Hardwood dowel (1/8" diameter x 12" long). 5. Hot glue gun and glue. 6. 8-1/2" x 11" sheet of heavy card stock, such as 90lb Bristol board. 7. Paper ruler, divided into millimeters (pick one from here, http://www.vendian.org/mncharity/dir3/paper_rulers/ ) 8. 3" x 1/2" x 16" piece of lumber for a base. 9. Sharp scissors. 10. A piece of #100 grit sandpaper or an emery board for filing a point onto the dowel. Assembly Prepare the Aneroid Chamber 1. Blow up the balloon to stretch it out, and then release the air. Cut off the neck of the balloon so that you can reach into the balloon with your fingers and stretch the balloon out and over the top of the cup.  Make sure that the inside surface of the ballon ends up on the outside so that humidity trapped in the inside of the balloon will not be trapped in the chamber. You may have to practice this several times to do it without ripping the balloon, yet at the same time obtaining a good seal over the top of the cup. Note: Some like to stretch out the balloon by simply pulling it in their hands. My personal bias is that this does not stretch the balloon uniformly. But blowing up heavy balloons is sometimes difficult for kids.
 2. Wrap several rubber bands around the top of the cup and over the balloon to help insure a tight air seal.
 Add The Pointer The long dowel will be glued to the balloon surface so that it extends from the center of the balloon outwards over the edge of the cup.  Use two dabs of glue; one at the center of the balloon and one at the rim of the cup.
 Assemble The Stand and Scale Load your computer printer with some heavy paper (80 lb Bristol board, cut to 8-1/2" x 11") and print this pattern on the paper.  Cut it out and fold it up to make the stand.  Glue (or double-stick tape) the "tabs" to the "base". Cut out and attach this ruler scale to the middle of the stand.  Put "zero" toward the base of the stand.
 Attach All Parts to the Base. 1.  Position the cup and scale/stand (without glue) onto the wood base.  See the picture below. 2.  Use hot glue to attach just the bottom edge of the cup to one end of the base by applying two or three blobs of glue, evenly spaced, around the outside edge of the cup.  Position the cup so that the end of the pointer is near the front edge of the base.  3.  Use a small sanding board to sharpen the end of the pointer so that its position can be determined precisely.  Then attach the scale/stand to the base so that the pointer is nearly touching the scale and is free to move up and down.  .