Introduction

 

A barometer is an instrument used to measure atmospheric pressure. Meteorologists track a series of changes in atmospheric pressure to forecast impending weather changes. Decreasing atmospheric pressure is a sign that rainy weather might be on the horizon.

To avoid complex issues common among high tech devices, we can use a simple barometer like the water barometer to measure changes in atmospheric pressure. A water barometer is a sealed glass container half filled with water. A narrow spout open to the atmosphere extends downward to the body of the glass container below the water line.

As air pressure increases, water level in the spout drops below the water level in the body of the glass container. As air pressure decreases, the water level in the spout rises above the water level in the body of the glass container.

Things You'll Need

  • Glass container with spout
  • Double sink (or equivalent)
  • Water
  • Food coloring

Instructions

Step 1 - Fill one side of sink or container with cold water; fill opposite side with very hot tap water. Depth of water must allow complete submersion of barometer (i.e., entire glass container).

Step 2 - Submerse barometer in hot water. Let water fill barometer. When air stops coming out of spout, place finger over mouth of spout. Takebarometer out of hot water, and submerse it in cold water.

Step 3 - Remove finger from mouth of spout, and water should be drawn into the spout. Repeat steps 2 and 3 until water in barometer is about 1/2 inch above the highest point where the spout meets the body of the barometer (glass container).

Step 4 - Let barometer sit for about an hour to allow water to reach room temperature. Then, turn the barometer upside down, letting half the water in the spout pour out. Add liquid food coloring to barometer to make the barometer easier to read. See the image at left.

Step 5 - Take note of where the water level in the spout is in relation to the water level in the body of the barometer.

Step 6 - Monitor changes in atmospheric pressure: As air pressure increases, water level in the spout drops below the water level in the body of the glass container. As air pressure decreases, the water level in the spout rises above the water level in the body.

Photo Credits

Wikimedia Commons