1. How is Air Pressure Measured

2. Mercury Barometer Air pressure is measured with an instrument called a barometer. A mercury barometer is a glass tube filled with mercury.

3. How a Mercury Barometer Works A numbered hollow tube sits in a container of mercury. As air pressure pushes the mercury down, it flows up the hollow tube. As air pressure changes, the level of the mercury in the tube rises or falls.

5. Another kind of barometer is called an aneroid barometer. The word aneroid means “without liquid”. Aneroid Barometer

6. How a Aneroid Barometer Works An aneroid barometer is made of an airtight metal container. When air pressure increases, the sides of the container bend in. When air pressure decreases, the sides of the container bend out. A needle measures the difference in air pressure.

7. Measuring Air Pressure Standard air pressure at sea level measures 760 mm of mercury. Air pressure is also measured in millibars (mb). Standard air pressure is equal to 1,013.20 mb.

8. An altimeter is a device used to measure altitude. Pilots, scientists, surveyors, and mountain climbers all use altimeters. Altimeter

9. Checking Concepts 1. Air pressure is measured with a ______ 2. Two kinds of barometers are mercury barometers and _________barometers. 3. The mercury column in a mercury barometer rises or falls with changes in ________. 4. Air pressure is measured in ___(hint: two letters).