1. AIR PRESSURE Chapter 1, Section 3 Pages 25-30

2. What properties does air have? Since it is made of atoms and molecules, which are made of matter, air must have… –Mass –Volume –Density-  the amount of matter in a given space (g/mL) –Pressure-  the force pushing on an area or surface.

3. What is AIR PRESSURE? How is air pressure measured?  Air pressure is the result of the weight of a column of air pushing down on an area.  That weight is measured with a barometer.  HIGH PRESSURE- fair weather or a clear sky  LOW PRESSURE- storm is approaching or a cloudy sky

4. Explain how air pressure is pushing down at approximately the weight of a bus, but does NOT crush anything?  Because air molecules are not only pushing down, but they are pushing in ALL directions

5. What is a Mercury barometer?  A mercury barometer consists of a glass tube open on the bottom end and partially filled with mercury.  The “empty” space in the tube is a vacuum…there is NO air in there!  As air pressure increases, the level of the fluid in the tube increases and visa-versa.

6. What is an aneroid barometer?  An aneroid barometer is an instrument that measures air pressure “without liquid.”  It consists of an airtight metal chamber sensitive to slight changes in air pressure.  As pressure increases, the thin walls push in and cause the dial moves, which is connected to springs, indicating an increase in pressure and visa-versa.

7. What are the two units used to measure air pressure?  Inches of mercury and millibars  Average air pressure is… –1013.25 millibars –29.92 inches

8. What is altitude?  Altitude, or elevation, is the distance above sea level, the average level of the surface of the oceans.

9. How does altitude affect air pressure? WHY?  Air pressure decreases as altitude increases.  A “larger column of air” has more molecules within it and creates more force than a “smaller column of air.”  As altitude increases the column or air gets smaller and smaller.

10. How does the density of air change as altitude increases?  As altitude increases, air pressure decreases and so does density.  If the air is LESS DENSE, then that means that there are FEWER molecules to create the force of pressure (air pressure.)