How to Make a Water Barometer

A barometer is a weather instrument that measures the pressure of the atmosphere, which indicates changes in the weather. As the barometer rises, you can expect warmer, drier weather; as it falls, the weather will become wetter and cooler. With a few things from around your house, you can make a simple water barometer that demonstrates the changes in air pressure. If you watch the weather as your water barometer works, you can see the relationship between air pressure and weather, as well.

Things You'll Need

• Tall drinking glass
• Food coloring
• Empty juice bottle
• Erasable marker

Instructions

1. Fill the tall drinking glass with water. Add some red food coloring to it, so the level of the water can be seen easily.

2. Invert the empty glass juice bottle and insert the bottle's mouth into the drinking glass. Use a juice bottle that fits snugly in the drinking glass, but is short enough that the mouth of the bottle does not touch the bottom of the drinking glass. The water should be high enough in the drinking glass that when the juice bottle is inserted into the glass, the water rises into the bottle.

3. Mark a line on the drinking glass with an erasable marker to show the starting water level in the glass.

4. Watch the water level in the glass for two days. If the air pressure has risen, the air pressure on the surface of the water in the glass rises, as well, and more water is forced into the juice bottle. As the water level in the juice bottle rises, the water level in the glass will be lower than the mark you made on the glass. If the air pressure drops, there will be less water the juice bottle and the the water level in the glass will rise above the mark you made on the glass.

Tips & Warnings

• The smaller the neck of the juice bottle, the more noticeable the change in the water level will be.

• Be sure to wash the erasable marker from the drinking glass after you disassemble your barometer.

References

• The Franklin Institute

Resources

• The Weather Glass