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How to Make a Barometer From a Coffee Can

A barometer measures air pressure, which is a key measurement that meteorologists use when they predict upcoming weather conditions. High air pressure tends to accompany stable weather that is sunny and dry, while low air pressure means that a storm may be on the way. The air around a barometer pushes liquid up through a gauge. The typical liquid used is mercury, and the number of inches this mercury extends up the gauge is the mesaurement of pressure. Using a coffee can and some other household items, you can make a simple barometer to show your children how a barometer works.

Things You'll Need

Coffee can
Rubber band
Index card
Drinking straw
Scissors
Plastic wrap

Instructions

- 1
  Tear enough plastic wrap from the roll to cover the top of the coffee can. Place it over the top and put a rubber band around the top of the can. Make sure the rubber band makes an airtight seal with the plastic wrap.
- 2
  Place the straw across the top of the can, so that about a third of it extends off one side. Tape the straw into place. Attach the index card to the back of the can with tape, so that is also behind the extended end of the straw.
- 3
  Make a line where the straw currently points on the card. After half an hour, mark where the straw points, and repeat several times. If the air pressure drops, the plastic will expand, pointing your straw downward. If the pressure rises, the plastic will sink, pushing the straw up.

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