 Air has mass ◦ Therefore air has density and pressure ◦ Density is the amount of mass in a given volume  DENSITY=MASS/VOLUME (kg/L)  MASS= DENSITY x VOLUME (kg)  VOLUME= MASS/DENSITY (L) ◦ If there are more molecules in a given volume, the density is greater. Less molecules in a given volume, the density is less

 If Spiderman has a mass of 90kg and has a volume of 30 liters, what is his density ◦ Density= mass/volume ◦ Density= 90kg/30L ◦ Density= 3kg/L

 On the same day and same time at Mount Everest, the air has a density of 75kg/L in a volume of 5 liters. What is the mass of the air? ◦ Mass=Density x Volume ◦ M= (75kg)(5L) ◦ M= 375 kg

 On the same day and same time in Miami, the air has a density of 130 kg/L in a volume of 5 liters. What is the mass of the air? ◦ M=DV ◦ M= (130kg/L)(5 L) ◦ M= 650 kg

 Ms. Zeidman’s brain has a mass of 28 kg and takes up a volume of 7 liters. What is the density of Ms. Zeidman’s brain? ◦ D=M/V ◦ D=28 kg/7L ◦ D= 4kg/L

 The density of Ms. Arangio’s 2 nd hour class is 12,500 kg/L and the mass is 200,000 kg. What is the volume of the class? ◦ V=M/D ◦ V= 200,000kg/12,500 kg/L ◦ V=16L

 Your table has a density of 750 kg/L and a mass of 100 kg. What is the volume of your table? ◦ V=M/D ◦ V=100kg/750kg/L ◦ V=.13L

 Pressure is the force pushing on an area or surface  Weight of the atmosphere exerts a force on surface and air pressure is the result of the weight of air pushing down on an area  The column of air extends through the entire atmosphere

 Molecules in air push in all directions therefore it does NOT crush us  Air pressure can change from day to day  Denser substances have more mass per unit volume than less dense substances so denser air exerts more pressure than less dense air

 Barometer ◦ Two kinds:  Mercury barometer consists of glass tube open at the bottom end and partially filled with mercury  Aneroid barometer has an airtight metal chamber and is most commonly used  Units of air pressure are “inches of mercury” and millibars  30 inches of mercury is approximately equal to 1,016 millibars

 Air Pressure and Altitude  Air Pressure decreases as altitude increases

 Altitude and Density  The density of air decreases as altitude increases. Air at sea level has more gas molecules in each cubic meter than air at the top of a mountain.

 Four Main layers classified according to changes in temperature ◦ Troposphere ◦ Stratosphere ◦ Mesosphere ◦ Thermosphere  Includes the ionosphere and exosphere  Know Figure 9 on pg. 523

 Lowest layer of the atmosphere  Weather occurs here  Goes 9-16km from the surface of the earth  Shallowest layer  Contains almost all of the mass of the atmosphere  As altitude increases, temperature decreases  At the top, the temp stays at about - 60degrees Celsius and water forms thin, feathery clouds of ice

 Extends from the top of the troposphere to about 50km above earth’s surface  Contains the ozone layer  The lower part is cold, about -60 degrees Celsius and the upper part is warmer because of the ozone layer ◦ Ozone layer gets heated from the sun

 Middle layer of the atmosphere  Begins 50km above earth’s surface and ends at an altitude of 80km above earth’s surface  Outer mesosphere is about -90degrees Celsius  Protects earth’s surface from being hit by most meteoroids

 Outermost layer of earth’s atmosphere  Extends 80km above earth’s surface and goes outward into space, no definite outer limit  Extremely hot up to 1800 degrees Celsius ◦ Because sunlight strikes the thermosphere first and nitrogen and oxygen molecules convert sun’s energy into heat ◦ Would not feel hot because there are not very many molecules in this layer

 Divided into two layers: ◦ Exosphere- the outer layer  Extend from about 400km outward thousands of kilometers ◦ Ionosphere- the lower layer  80km above the surface and extends about 400km  Energy from sun cause gas molecules to become electrically charged particles called ions  Radio waves bounce off ions- make brilliant light displays called Auroras