Air Pressure 5.4 Ms. De Los Rios 6 th Grade

1. Weather Factors Air Pressure 5.4 Ms. De Los Rios 6th Grade

2. Vocabulary 5.4 • Density- the ratio of mass of a substance to its volu/me • (mass by volume) • Air Pressure: The pressure caused by the weight of air pushing • Down on an area. • Barometer: An instrument used to measure changes in air pressure. • Mercury Barometer: An instrument that measures in air pressure, consisting of a glass tube filled with mercury, with its opened air resting in a dish of mercury. • Aneroid Barometer- An instrument that measures changes in air pressure without using a liquid. • Altitude- Elevation above sea level.

3. What are Some Properties of Air? • Do you see air? • Air is made up of atoms and molecules, which have mass. • Mass properties= density, pressure • Because air has mass, it also has other properties, including density and pressure. • (more molecules= more density, less molecules= less density) • Density (mass by volume) • The amount of mass in a given volume it occupies of air is its density. You calculate the density of a substance by dividing its mass by its volume. • volume (Volume is the amount of space enclosed by a shape or object, how much 3-dimensional space (length, width, and height)

4. What are Some Properties of Air? Pg. 171 • Air Pressure • Atmosphere is heavy. • The force pushing on an area or surface is called pressure. • Air pressure is the result of the weight of a column of air pushing on an area. • The reason air pressure does not crush you is because the molecules in air push in all directions. • So the air pushing down • is balanced by the air pushing up.

5. Air Pressure Air Column The weight of the column of air above you puts pressure on you. How does pressure from air molecules keep you from being crushed?

6. What instruments Measure Air Pressure? • Air pressure can change daily. • A barometer is an instrument that is used to measure air pressure. Two types of barometers are: • mercury barometers and aneroid barometers. • A mercury barometer consists of a long glass tube that is closed at one end and open at the other. The open end rests in a dish of mercury. The closed end contains very little air. Increases in air pressure force the column of mercury higher in the tube. The level of the mercury in the tube shows the pressure of the air that day.

7. Air Pressure Reading a Mercury Barometer What would a low air pressure reading look like?

8. What instruments Measure Air Pressure? • Aneroid= means without liquid • An aneroid barometer has an airtight metal chamber. • When air pressure increases, the thin walls of the chamber are pushed in. • When air pressure drops, the walls bulge out. • As the chamber’s shape changes a needle on the dial moves. • Weather reports air pressure in inches of mercury. • National Weather Service maps indicate air pressure in millibars. • One inch of mercury equals about 33.86 millibars.

9. Air Pressure Inside an Aneroid Barometer An aneroid barometer has an airtight metal chamber, shown in red. Which diagram shows the aneroid barometer under high pressure and which shows it under low pressure?

10. How Does Altitude Affect Air Pressure and Density? • Altitude, or elevation, is distance above sea level. • Air pressure decreases as altitude increases. • As air pressure decreases, so does density. • Because air is less dense at a high altitude, each cubic meter of air you breathe has fewer oxygen molecules than at sea level. So you would become short of breath more quickly at a high altitude.

11. How Does Altitude Affects Air Pressure? Pg. 174 • Air at sea level has the weight of the whole atmosphere pressing on it. • The air at the top of a mountain has less weight pressing on it, therefore having lower air pressure.

12. Air Pressure Effect of Altitude on Pressure and Density How densely packed would the molecules be at the different altitudes?