Docstoc

Balloon Animals

Document Sample
Balloon Animals Powered By Docstoc
					           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

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:3
posted:1/30/2012
language:
pages:15