How to Build a Barometer to Measure Air Pressure

This simple tool is a wonderful way to observe and learn about changes in air pressure.

It also integrates nicely with other weather machines, anemometer, wind compass, hygrometer – and with cloud studies activity.

Barometer – Measure Air Pressure

Materials:

1. clear, straight-neck glass bottle (about 12 oz.)
2. clear glass jar (about 18 oz.)
3. food coloring
4. rubber band
5. straight pin
6. pot with water for testing the idea
7. notebook, pen or pencil
8. (optional) webcam or camcorder

Procedure:

1. Clean all labels from the jar and bottle.
2. Fill the jar with water to just over the mouth by an inch.
3. Add a few drops of food coloring.
4. Tip the bottle and jar enough to let air bubbles escape.
5. Slide the rubber band onto the jar. Position it at the same level as the water.
6. Place the barometer in a place out of direct sunlight but where it is visible.

As the water rises and falls in the neck of the bottle, use the rubber band
to mark the new level.

Testing this idea:
Take a large cooking pot and fill it with water. What happens to the water
level when you press down on it? What happens when you remove your hands?

Can you relate to how the non visible air around you would follow the same pattern?

High pressure happens when air is pressing down on the earth. What does your barometer do when there is high pressure? Low pressure happens when the air is rising. What happens to your barometer?

What do the clouds look like when there’s high pressure and when there’s low pressure? Do you notice patterns during morning, afternoon or evening observations?

Use your webcam or camcorder to keep track of weather changes.