# Balloon Animals by dffhrtcv3

VIEWS: 3 PAGES: 15

• pg 1
```									           Announcements
• Survey on Sakai
• Homework 1 on class web site (also
available on Sakai)
• Quiz 1 available on Sakai after class (10
points)
• Pre-test on Sakai (10 points)
Atmospheric Physics

what drives the weather
Specific Heat
How much energy it takes to raise the
temperature of a substance
• The same energy input raises the
temperature of land more than water
– or–
• It takes more energy to raise the
temperature of water than land
Expanding and Contracting
• Compressing a gas adds energy to it
– Its molecules speed up
– Its temperature rises
• A gas expanding against its surroundings
loses energy
– Its molecules slow down
– Its temperature drops
Expanding and Contracting
• The same amount of gas occupies more
volume at a higher temperature.
• That same volume of cool air weighs
more.
• Cool air sinks, pushing warm air up.
Convection
• Hot water stayed on top, cold stayed on
the bottom
• Hot water moved to the top, cold to the
bottom (with mixing)
Phase Changes
• Melting, boiling, freezing, condensing…
• Water freezes at 0 °C, boils at 100 °C (well,
at 92 °C in Laramie)
• Not all heat transfer is expressed as a
temperature change.
Evaporation of a Liquid
• More energetic jostling = higher
temperature
• An especially fast molecule at the surface
may detach!
Evaporation of a Liquid
• More energetic jostling = higher
temperature
• An especially fast molecule at the surface
may detach!
Evaporation
• Evaporating molecules carry away energy
• Remaining liquid cools (lower energy)
Latent heat
• Energy required to change the phase of 1
kg of substance
• Water’s latent heat of fusion (melting):
335,000 J/kg = 80 Cal/kg
• Water’s latent heat of vaporization:
2,255,000 J/kg = 539 Cal/kg
Heating Curve for Water

Water temperature with heating
200
150                          Water boils            steam
temperature (C)

100
50 Ice melts                              Liquid water
0
-50                                                    ice
-100
0.0E+00       1.0E+06       2.0E+06         3.0E+06   4.0E+06
heat input (J/kg)
Condensation
• Vapor condenses to liquid only when:
– its concentration is high enough and
– its temperature is low enough
• Rising humid air forms clouds
– air rises and cools
– moisture condenses to droplets
Condensation
• Vapor condenses to liquid most easily on
a surface (solid or liquid)
– Wall of the bottle
– Smoke particles
Layers of the Atmosphere
thermosphere   Heated from sun, solar wind
very rarefied

Heated from stratosphere
mesosphere     very rarefied

Heated by sun on ozone
stratosphere   temperature rises with altitude
not mixed
Heated from surface
troposphere    temperature drops with altitude
strongly mixed
surface

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