Water Barometer

What you need:Water barometer experiment
• glass or jar
• bowl
• 3 coins
• pen
• water

What you do:
• Fill the glass about two-thirds full with water.
• Place the bowl upside down over the glass.
• Carefully turn the bowl and the glass over so that the glass sits upside down in the bowl.
• Some of the water will run out of the glass but most will stay inside it.
• Slide the coins under the rim of the glass and space them equally around the rim.
• With a pen mark the level of the water in the glass at the beginning of the activity.
• Take your barometer outside into the open air.
• Look for changes in the water level in the glass over time. (This may take several hours or even longer than a day.)

How it works: When the atmospheric pressure of the air rises, the water in the bowl will be forced downwards by the weight of the air on the water. This, in turn, will cause the water in the glass to rise. A barometer measures the weight of the amount of air between the surface of the earth (the water in the bowl) and the top of the atmosphere.

DIY Barometer

What you need:barometer
• Scissors
• Tape
• Balloon
• Jar
• Elastic rubber band
• Straw

What you do:
• Cut the balloon in half.
• Discard the piece with the neck on it.
• Take the remaining piece of the balloon and stretch it across the glass or jar.
• Keep it stretched firmly across and seal it down with the rubber band, around the rim of the glass jar.
• Tape the straw onto the balloon lid; the straw should be sitting one quarter of a way on the lid, with the tape about 1 inch from the edge of the straw end that is sitting on the balloon lid. The straw is your indicator “needle”.
• Trim the straw if it’s too long, but leave more length off the jar as what is attached to it.
• Put the finished glass jar next to a wall and tape a piece of paper or card to the wall behind it.
• Mark the current position of the straw on the paper, and mark one above and below the mark, about the same length away, and label the high and low pressure.
• Check the straw regularly and keep marking its location on the paper for a few days.