Teacher Demos Chapter 26: Atmosphere
Mass, Volume and Adiabatic Heating/Cooling
I.
Volume, Mass and Density of Air
A.
Volume: Thistle Tube w/KMnO4 water
Air takes up ____________________
B.
Mass:
1.
Weigh an empty balloon: _______________
2.
Inflate the balloon until it is spherical
3.
Weigh the inflated balloon: _________________
Air has _________________________
C.
Estimated Density of the air…
D = M/V
1.
Estimate the Volume of the inflated balloon
V = (4/3)πR3
a)
Find the radius of the inflated balloon
Circumference = π* diameter
C=d
π
d/2 = radius: _______________________
b)
Calculate the volume
V=4/3*3.14*R3
c)
Calculate the Density
D= M/V
Extra Credit: show with calculations how closely our experimentally determined value is to the
commonly accepted value for density of the air, which is 1.2 Kg/M3
Demos: Mass, Volume and Adiabatic Heating/Cooling – cont’d
II.
Adiabatic Heating and Cooling #1: Fire Piston
A.
What happens to the temperature in the fire piston when pressure
increases?
1.
What would happen to temp if pressure decreases?
a) What would happen to pressure if temp increases?
b) What would happen to pressure if temp decreases?
B.
Adiabatic Heating in the Atmosphere:
1.
Change in ___________________ associated with rising or
sinking air
a)
Rising Air: Cooling with Expansion - Adiabatic Lapse Rate
b)
Sinking Air: Heating with Compression - Chinook Winds
c)
Science Factoid: These relationships between pressure volume
and temperature are known as “gas laws”
PV=T
Boyles Law - Pressure and Volume
http://group.chem.iastate.edu/Greenbowe/sections/projectfolder/flashfil
es/gaslaw/boyles_law_graph_new.swf
Charles Law - Temperature and Volume
http://group.chem.iastate.edu/Greenbowe/sections/projectfolder/flashfil
es/gaslaw/charles_law.swf
Demos: Mass, Volume and Adiabatic Heating/Cooling – cont’d
III.
Adiabatic Heating and Cooling #2: Cloud in a bottle
A.
What happens when we quickly reduce the pressure inside a bottle
with humid air?
B.
What happens to the cloud when we re-pressurized the bottle?
C.
1.
The cloud…
2.
Our explanation:
a)
↑ Pressure = __________________ temperature
b)
↑ Temperature causes droplets to __________________
What happens to temperature when pressure again decreases?
1.
↓ Pressure = __________________ temperature
a)
↓ Temperature = holds less ______________ vapor so
water molecules condense around particles of smoke, dust or
salt resulting in the formation of a _____________
IV.
Adiabatic Heating of Moist Air in the Atmosphere
The temperature change associated with rising or sinking air as it is affected by
evaporation or condensation of water
A.
The Moist Adiabatic Lapse Rate depends on moisture vapor in the air
1.
Little moisture = not much effect
 air cools nearly 5.5ºC/1,000 feet – just like the dry adiabatic lapse rate
2.
Air with lots of moisture (that is saturated) = big effect
 Air cools at only 2-3 /1000 meters (stays warmer as it rises)
 in the meantime water vapor is condensing and forming
_____________________