Air pressure is measured by observing the height of the column of mercury in the tube. At sea level, air pressure will push on the mercury at the open end and support a column of mercury about 30 inches high. If you used water instead of mercury, you would need a glass tube over 30 feet in length. Control the Weather To see how weather and pressure are linked, move your mouse over the scale lines on the barometer to the left and observe what happens to the picture above. Narrow-neck glass bottle.
Instructions Insert a drinking straw into the bottle.
Fill the bottle about half-way full of water. Seal the neck of the bottle around the straw either with the rubber stopper or a cork. Make sure the end of the straw is immersed in the water and that the water level in the straw is above the top of the bottle. As the air pressure outside the bottle decreases, the trapped air inside the bottle will push the water up the straw. As the air pressure outside the bottle increases, it will push the water farther down the straw.